Diagrams showing the internal wiring structure of the Bosch 1.3 DME electronic control unit for injected BMWs that use it, E30, E28, E34, etc...
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Showing posts with label guide. Show all posts
Showing posts with label guide. Show all posts
Thursday, 15 June 2023
Wednesday, 14 June 2023
BMW DME Bosch Motronic 1.1 - 1.3 Complete Guide (Equiptech)
Superb guide from the guys at Equiptech all about the Bosch Motronic 1.1 and 1.3 for the E30 and other BMWs...
Motronic 1.1 and 1.3
Motronic 1.1 and 1.3 are an evolution of the early Motronic EMS fitted to previous BMW vehicles during the early to middle 1980's. Motronic 1.1 was first fitted to some 6 cylinder models in 1987 and was superseded in 1988 by Motronic 1.3. The main differences between 1.1 and 1.3 concern the SD feature. 1987 versions of M1.1 contained some small differences to the 1988 version. The Motronic EMS is a fully integrated system that controls primary ignition, fuelling and idle control from within the same ECU. Although only 6 cylinder engines were equipped with M1.1, when M1.3 was introduced, both 4 and 6 cylinder engines were equipped with this later version.
The ignition point and injection duration are jointly processed by the ECU so that the best moment for ignition and fuelling are determined for every operating condition. The injection function of the Motronic system is based on the well tried 'L' jetronic system, although a number of refinements have improved operation. A 55 pin connector and multi-plug connects the ECU to the battery, sensors and actuators.
Basic ECU operation
A permanent voltage supply is made from the vehicle battery to pin 18 of the ECU. This allows the self-diagnostic function to retain data of an intermittent nature. Once the ignition is switched on, a voltage supply to ECU pin 27 (not 1987 M1.1) and to the ignition coil is made from the ignition switch. This causes the ECU to connect pin 36 to earth, so actuating the main fuel injection relay. A relay switched voltage supply is thus made to ECU pin 37, from terminal 87 of the main fuel injection relay. The 1987 M1.1 system relay is connected to earth and not to the ECU. However, once the ignition is switched on the relay operation is similar to later models.
The majority of sensors (other than those that generate a voltage such the CAS, CID, KS and OS), are now provided with a 5.0 volt reference supply from a relevant pin on the ECU. When the engine is cranked or run, a speed signal from the CAS causes the ECU to earth pin 3 so that the fuel pump will run. Ignition and injection functions are also activated. All actuators (Injectors, ISCV, CFSV etc), are supplied with nbv from the main relay and the ECU completes the circuit by pulsing the relevant actuator wire to earth.
Signal processing
Basic ignition timing is stored in a two dimensional map and the engine load and speed signals determines the ignition timing. The main engine load sensor is the AFS and engine speed is determined from the CAS signal.
Correction factors are then applied for starting, idle, deceleration and part and full-load operation. The main correction factor is engine temperature (CTS). Minor correction to timing are made with reference to the ATS and TS signals. In addition, other factors that influence ignition timing are signals from the Electronic Throttle Control, Automatic Stability Control, Engine Torque Control and Electronic Transmission Control where all or any of these components are so fitted.
The basic AFR is also stored in a two dimensional map and the engine load and speed signals determines the basic injection pulse value. Motronic calculates the AFR from the AFS signal and the engine speed (CAS).
The AFR and the pulse duration are then corrected on reference to ATS, CTS, battery voltage and position of the TS. Other controlling factors are determined by operating conditions such as cold start and warm-up, idle condition, acceleration and deceleration.
In models with an ISCV, Motronic accesses a different map for idle running conditions and this map is implemented whenever the engine speed is at idle. Idle speed during warm-up and normal hot running conditions are maintained by the ISCV. However, Motronic makes small adjustments to the idle speed by advancing or retarding the timing, and this results in an ignition timing that is forever changing during engine idle.
Adaptive function
The ECU is adaptive to changing engine operating characteristics and constantly monitors the data from the various sensors (ie MAP, ATS, CTS and TPS). As the engine or its components wear, the ECU reacts to new circumstances by adopting the changed values as a correction to the basic Map.
When the adaptive map is used in conjunction with the OS, Motronic is able to respond much more quickly and retain tighter control over the changing gases in the exhaust system. During closed loop operation the basic injection value is determined by the values stored in the map for a specific rpm and load. If the basic injection value causes exhaust emissions outside of the Lambda value (ie 0.98 to 1.04 AFR) the mixture would be too rich or too lean and the OS would signal Motronic which in turn will correct the mixture. However, this response takes a little time and so Motronic learns a correction value and adds this 'Adaptive' values to the basic map. From now on, under most operating conditions, the emissions will be very close to Lambda and so, after reference to the OS signal, the ECU will only need to make small corrections to keep it that way.
Adaption and correction of the map occurs during the following engine operations. CFSV operation
ISCV operation
Idle mixture adjustment
part load mixture adjustment
Operation of the CFSV introduces a combustible mixture to the engine that is compensated for by the fuel evaporation adaptive correction values after detection by the OS..
Self Diagnostic function
The Motronic 1.3 system has a self-test capability that regularly examines the signals from engine sensors and internally logs a code in the event of a fault being present. This code can be extracted from the Motronic Serial Port by a suitable Fault Code Reader. If the fault clears, the code will remain logged until wiped clean with a suitable FCR, or until the engine has been started for more than 5 times - when the fault code is self initialising. An ECU that retains codes for faults of an intermittent nature is a valuable aid to fault diagnosis.
Motronic 1.1 1987 to 1988: The ECU will store a maximum of 5 fault codes.
Motronic 1.3 from 1989: The fault code memory is extended to contain all fault codes that are detected by the EMS.
In vehicles sold in the USA, when the ECU detects that a some faults are present it earths pin 15 and the Check Engine warning lamp on the dash will light. The lamp will stay lit until the fault is no longer present. A warning lamp is not fitted to vehicles sold in other markets. The faults that will turn on the lamp are mainly those concerned with emissions. Other faults are logged by the ECU but the lamp will remain out.
Limited Operating Strategy (LOS)
In the event of a serious fault in one or more of the sensors or their wiring circuits, Motronic will substitute a fixed default value in place of the defective sensor. This procedure is often termed limp home. A serious fault occurs when the signal from the sensor is outside of its normal operating parameters.
When operating in LOS the engine may actually run quite well with failure of one or more minor sensors. Since the substituted values are those of a hot engine, cold starting and running during the warm-up period may be less than satisfactory. Also, failure of a major sensor, ie the AFS, will tend to make driving conditions less easy. Once the fault has cleared, Motronic will once more accept the live signal from the sensor. The following LOS measures are taken in the event of a failure
Component AFS
ATS
CID sensor CO pot CTS
OS TS
Action
substitute values are calculated from the TS position. The load signal is fixed to 6.0 ms and the ignition timing to 20° BTDC once the TS contact is open.
substitute value of 50° C . A code will not be set, and LOS will not commence until a minimum of 3 minutes after engine start and the engine idling for a minimum of 30 seconds.
injectors are pulsed simultaneously
substitute value of 2.77 volts
substitute value of 80° C if ATS value is greater than 20° .
if ATS value is less than 20° , substitute value of ATS value for first three minutes after engine start-up .
substitute value, open loop control
substitute values, restricted engine operation
Anti-theft protection
When the drive-away code is entered upon the on-board computer, or when the anti-theft system is armed, a signal is sent to Motronic which switches off the ignition and injection functions.
Automatic Stability Control (ASC)
ASC is integrated with ABS and is located in the ABS Electronic Control Unit. The rotational speed of the wheels is monitored by the ABS ECU via the ABS wheel sensors. If the rotational speed between the driven and non-driven wheels is vastly different, the ECU interprets this as wheel spin. Depending on the degree of wheel spin, the ABS ECU may take one or more of the following actions.
Instruct the Electronic Throttle Control to reduce the throttle opening angle.
Instruct the Motronic ECU to retard the ignition timing angle.
Instruct the Motronic ECU to cut off ignition and injection functions.
Engine Drag Torque Control
Torque control occurs when wheel slip occurs during deceleration. Engine Drag Torque Control is also integrated with ABS and is located in the ABS Electronic Control Unit. The rotational speed of the wheels is monitored by the ABS ECU via the ABS wheel sensors. If the rotational speed of the driven wheels is vastly different to the non-driven wheels during deceleration, the ECU interprets this as wheel spin. Depending on the degree of wheel spin, the ABS ECU may take one or more of the following actions.
Instruct the Motronic ECU to de-activate the deceleration fuel cut-off function.
Instruct the Electronic Throttle Control to adapt the throttle opening angle until wheel spin is reduced.
Service lights
There is a cluster of LED's on the dash: five green, one red and one Yellow. Up to five green LED's will light when the ignition is turned on. However, the LED's will extinguish once the engine is started. When the yellow light comes on , service is due. When the Red light comes on, this means that service is overdue by approximately 1000 miles & should be attended to immediately. Once the service has been completed, the service lights should be reset .
Reference voltage
Voltage supply from the ECU to many of the engine sensors is at a 5.0 volt reference level. This ensures a stable working voltage unaffected by variations in system voltage.
The earth return connection for most engine sensors is made through an ECU pin that is not directly connected to earth. The ECU internally connects that pin to earth via one of the ECU pins that are directly connected to earth.
Signal shielding
To reduce RFI, a number of sensors (ie CAS, KS and OS) use a shielded cable. The shielded cable is connected to the main ECU earth wire at terminal 19 to reduce interference to a minimum.
Maximum speed cut-off
Once the engine speed reaches a pre-determined limit (4 cyl: 6200 ± 40), (6 cyl: 6400 ± 40), Motronic cuts off injector operation so limiting the maximum rpm possible.
Deceleration fuel cut-off
When the engine speed is above 1000 . . 1200 rpm with the throttle closed, Motronic cuts off injector operation and retards the ignition timing as an economy aid. As the engine speed falls below the threshold value, injection is re-instated and the timing advances. The point at which injection is re-instated depends upon engine temperature and the drop in rpm.
CAS
The CAS in the early Motronic system utilised two sensors to provide speed and position signals to the ECU. However, in M1.1/1.3 the primary signal to initiate both ignition and fuelling emanates from a single CAS mounted in proximity to the flywheel. The CAS consists of an inductive magnet that radiates a magnetic field. A number of steel pins are set into the periphery of the flywheel at 10 intervals. As the flywheel spins, and the pins are rotated in the magnetic field, an AC voltage signal is delivered to the ECU to indicate speed of rotation. In addition, a reference mark to TDC also indicates crankshaft position as the flywheel spins.
The peak to peak voltage of the speed signal (when viewed upon an oscilloscope) can vary from 5 volts at idle to over 100 volts at 6000 rpm. Because computers prefer their data as on/off signals, an analogue to digital converter transforms the AC pulse into a digital signal.
Ignition
Data on load (AFS), engine speed (CAS), engine temperature (CTS) and throttle position (TS) are collected by the ECU, which then refers to a three dimensional digital map stored within its microprocessor. This map contains an advance angle for each operating condition, and thus the best ignition advance angle for a particular operating condition can be determined.
Ignition timing
It is not possible to adjust the ignition timing on the Motronic 1.3 system.
Amplifier
The Motronic amplifier contains the circuitry for switching the coil negative terminal at the correct moment to instigate ignition. The amplifier circuitry is contained within the ECU itself and the microprocessor holds a map containing the correct ignition dwell period for each condition of engine speed and battery voltage. The signal received by the amplifier from the trigger is of an insufficient level to complete the necessary coil switching. The signal is thus amplified to a level capable of switching the coil negative terminal. One disadvantage of an internal amplifier, is that if the amplifier fails, the whole ECU must be renewed.
Dwell operation in Motronic is based upon the principle of the `constant energy current limiting' system. This means that the dwell period remains constant at around 4.0 to 5.0 ms, at virtually all engine running speeds. However, the dwell duty cycle, when measured in percent or degrees, will vary as the engine speed varies. A current limiting hump is not visible when viewing an oscilloscope waveform.
Ignition coil
The ignition coil utilises low primary resistance in order to increase primary current and primary energy. The amplifier limits the primary current to around 8 amps and this permits a reserve of energy to maintain the required spark burn time (duration).
Distributor
In the Motronic system, the distributor only contains secondary HT components (distributor cap, rotor and HT leads) and serves to distribute the HT current from the coil secondary terminal to each spark plug in firing order.
Cylinder Identification (CID)
An cylinder identification sensor is used to identify cylinder firing sequence. The sensor is connected around the HT lead of cylinder number 4 (4 cylinder) or cylinder number 6 (6 cylinder) adjacent to the distributor. As the HT pulses travel along the HT lead, a small AC signal is induced in the sensor and returned to the ECU. The ECU utilises an ADC to transform the signal into a digital pulse.
Fuel injection
The Motronic ECU contains a fuel map with an injector opening time for basic conditions of speed and load. Information is then gathered from engine sensors such as the AFS, CAS, CTS, and TS. As a result of this information, the ECU will look-up the correct injector pulse duration right across the engine rpm, load and temperature range.
The injectors are arranged in two banks with injectors 1 and 3 (4 cylinder) or 1, 3 and 5 (6 cylinder comprising one bank, and injectors 2 and 4 (4 cylinder) or 2, 4 and 6 (6 cylinder) making up the other bank. Each bank is connected to the ECU via an independent ECU pin.
The Motronic 1.1 & 1.3 multi-point injection system pulses the injectors semi-sequentially and once every two engine revolutions. During engine start-up below 600 rpm the ECU pulses all injectors simultaneously. Once 600 rpm has been attained and if the ECU has received a signal from the CID sensor, each injector bank will be pulsed alternatively according to which pair of cylinders are approaching TDC. If a signal is not received from the CID sensor the injectors will remain on simultaneous operation. However, if the CID sensor subsequently sends a signal to the ECU after the engine has commenced running, the ECU will pulse the injectors semi-sequentially after the next deceleration phase - even if the CID sensor then ceases to send a signal.
During start-up from cold, injector pulse duration is increased to provide a richer air/fuel mixture and pulse frequency is also increased. In addition, the ignition timing is also retarded. Injector frequency & pulse duration and degree of timing retard depend upon the engine temperature both during start-up and immediately afterwards. If the engine is restarted within one minute of the first start occurance, less overall fuel is injected to reduce the risk of fuel flooding into the engine.
Fuel injectors
The fuel injector is a magnetically operated solenoid valve that is actuated by the ECU. Voltage to the injectors is applied from the main relay and the earth path is completed by the ECU for a period of time (called pulse duration) of between 1.5 and 10 milliseconds. The pulse duration is very much dependant upon engine temperature, load, speed and operating conditions. When the magnetic solenoid closes, a back EMF voltage of up to 60 volts is initiated.
The fuel injectors are mounted in the inlet stubs to the engine inlet valves so that a finely atomised fuel spray is directed onto the back of each valve. Since the injectors are pulsed in two banks, fuel will briefly rest upon the back of a valve before being drawn into a cylinder.
Air Flow Sensor (AFS)
The AFS is located between the air filter and the throttle body. As air flows through the sensor it deflects a spring loaded vane (flap). The greater the volume of air, the more will the flap be deflected. The vane is connected to a wiper arm which wipes a potentiometer track and so varies the resistance of the track. This allows a variable voltage signal to be returned to the ECU. The voltage signal varies in proportion to the volume of air that flows through the vane.
Three wires are used by the circuitry of this sensor and it is often referred to as a three wire sensor. A 5 volt reference voltage is applied to the resistance track with the other end connected to the AFS earth return circuit. The third wire is connected to the wiper arm.
From the voltage returned, the ECU is able to calculate the volume of air (load) entering the engine and this is used to calculate the main fuel injection duration. To smooth out inlet pulses, a damper is connected to the AFS vane. The AFS exerts a major influence on the amount of fuel injected.
ATS
The ATS is mounted in the AFS inlet tract and measures the air temperature before it enters the inlet manifold. Because the density of air varies in inverse proportion to the temperature, the ATS signal allows more accurate assessment of the volume of air entering the engine. However, the ATS has only a minor correcting effect on ECU output.
The open circuit supply to the sensor is at a 5.0 volt reference level and the earth path is through the AFS earth return circuit. The ATS operates on the NTC principle. A variable voltage signal is returned to the ECU based upon the air temperature. This signal is approximately 2.0 to 3.0 volts at an ambient temperature of 20° C and reduces to about 1.5 volt as the temperature rises to around 40° C.
CO pot
The CO pot mixture adjuster is a three wire potentiometer that allows small changes to be made to the idle CO. A 5.0 volt
reference voltage is applied to the sensor and connected to the AFS earth return circuit. The third wire is the CO pot signal.
As the CO pot adjustment screw is turned the change in resistance returns a voltage signal to the ECU that will result in a change in CO. The CO pot adjustment only affects idle CO. Datum position is usually 2.50 volts. On catalyst equipped models, the CO pot has no effect and the CO is thus non-adjustable.
CTS
The CTS is immersed in the coolant system and contains a variable resistance that operates on the NTC principle. When the engine is cold, the resistance is quite high. Once the engine is started and begins to warm-up, the coolant becomes hotter and this causes a change in the CTS resistance. As the CTS becomes hotter, the resistance of the CTS reduces (NTC principle) and this returns a variable voltage signal to the ECU based upon the coolant temperature.
The open circuit supply to the sensor is at a 5.0 volt reference level and this voltage reduces to a value that depends upon the resistance of the CTS resistance. Normal operating temperature is usually from 80° to 100° C.
The ECU uses the CTS signal as a main correction factor when calculating ignition timing and injection duration.
Throttle switch
A throttle switch with dual contacts is provided to inform the ECU of idle position, deceleration, cruising and full-load (WOT) conditions. When the engine is at idle the idle contact is closed and the full-load contact is open. As the throttle is moved to the fully open position, the full-load contact closes and the idle contact becomes open. Under cruising conditions with a part-open throttle, both contacts are open. During full-load operation, the ECU provides additional enrichment. During closed throttle operation above a certain rpm (deceleration), the ECU will cut-off fuel injection. Injection will be reintroduced once the rpm returns to idle or the throttle is opened.
Electronic throttle control
Some models are equipped with Electronic throttle control, the so-called 'drive by wire' system whereby the mechanical control using a throttle cable is discontinued. A TS is not used on vehicles equipped with Electronic throttle control and the position of the throttle valve is signalled to the ECU electronically.
ISCV (2 wire type)
The ISCV is a solenoid controlled actuator that the Motronic ECU uses to automatically control idle speed during normal idle and during engine warm-up. Motronic detects the engine idle situation from the position of the TS or TPS. The ISCV is located in a hose that connects the inlet manifold to the air filter side of the throttle plate. A voltage supply is applied from the main relay and the ISCV earth is actuated by the ECU according to load.
When an electrical load, such as headlights, A/C or heater fan etc are switched on, the idle speed would tend to drop. The ECU will sense the load and rotate the ISCV against spring tension to increase the air flow through the valve and thus increase the idle speed. When the load is removed, the ECU will pulse the valve so that the air flow is reduced. Normal idle speed should be maintained under all cold and hot operating conditions. If the ISCV fails it will fail in a fail-safe position with the aperture almost closed. This will provide a basic idle speed.
ISCV (3 wire type)
The ISCV is a solenoid controlled actuator that the Motronic ECU uses to automatically control idle speed during normal idle and during engine warm-up. The ISCV is located in a hose that connects the inlet manifold to the air filter side of the throttle plate. Unlike the two pin ISCV which is controlled by a separate Idle speed ECU, the 3 pin ISCV is controlled by the Motronic ECU via ECU pins 33 and 34.
The ISCV is a DC motor that the ECU can rotate either clockwise or anti-clockwise. Rotating in one direction will open the valve and rotating in the opposite direction will cause it to close. A voltage supply is applied to the ISCV from the battery and the earth for the motor is made through two connections to the ECU.
Rotation of the motor in the appropriate direction is accomplished by actuating the motor through one or the other of the earth circuits. In reality the two circuits are opposed. This prevents the valve from being fully opened of closed in one particular direction. The valve will thus take up an average position that reflects circuit bias to be open or closed. Normally, this bias would be towards the open position.
A duty cycle can be measured on each earth circuit to determine the opening or closing time period as a percentage of the total time available.
When an electrical load, such as headlights or heater fan etc are switched on, the idle speed would tend to drop. The idle ECU will sense the load and rotate the ISCV to increase the air flow through the valve and thus increase the idle speed. When the load is removed, the ECU will pulse the valve so that the air flow is reduced. Normal idle speed should be maintained under all cold and hot operating conditions. If the ISCV fails it will fail in a fail-safe position with the aperture almost closed. This will provide a basic idle speed.
Relays
The Motronic electrical system is controlled by a main fuel injection relay and a fuel pump relay. A permanent voltage supply is made to the main relay terminals 30 and 86 from the battery positive terminal. When the ignition is switched on, the ECU earths terminal 85 through ECU terminal number 36 which energises the first relay winding (on the 1987 M1.1 system, this connection was made directly to earth). This causes the first relay contacts to close and terminal 30 is connected to the output circuit at terminal 87. A voltage supply is thus output at terminal 87. Terminal 87 supplies voltage to the injectors, ECU terminal 37, ISCV and the CFSV when fitted. In addition voltage is supplied to the fuel pump relay terminal 86.
When the ignition is switched on. the ECU briefly earths fuel pump relay contact 85 at ECU terminal 3. This energises the relay winding, which closes the relay contact and connects voltage from terminal 30 to terminal 87, thereby providing voltage to the fuel pump circuit. After approximately one second, the ECU opens the circuit and the pump stops. This brief running of the fuel pump allows pressure to build within the fuel pressure lines, and provides for an easier start.
The fuel pump relay circuit will then remain open until the engine is cranked or run. Once the ECU receives a speed signal from the CAS, the relay winding will again be energised by the ECU, and the fuel pump will run until 3 seconds after the engine is stopped. The 3 seconds delay in switching off the pump relay allows the fuel pump to maintain pressure on engine shut-off to avoid engine run-on.
In addition, on some vehicles control of the OS heater is made through a separate OS relay. Once the ignition is switched on, a voltage supply is made to the OS heater relay terminals 30 and 86. When the engine is started, the ECU connects relay terminal 85 to earth through ECU pin 23. The relay actuates and the output voltage at terminal 87 provides voltage to the OS heater. The ECU switches off the relay under certain conditions of speed and load.
Fuel pressure system
From build date 3/1988 the BMW vehicles in the Motronic 1.3 range were mounted internally in the fuel tank. Prior to that date the pump was mounted externally and in some instances an additional internal transfer pump was fitted to aid the pumping of fuel from the fuel tank.
internal pump operation (where fitted)
The fuel pump assembly comprises an outer and inner gear assembly termed a gerotor. Once the pump motor becomes energised, the gerotor rotates and as the fuel passes through the individual teeth of the gerotor, a pressure differential is created. Fuel is drawn through the pump inlet, to be pressurised between the rotating gerotor teeth and discharged from the pump outlet into the fuel supply line. When both an internal and external pump are fitted, the internal pump is ancillary to the main external pump and is provided to aid the pumping of fuel from the fuel tank.
external pump operation (where fitted)
A roller type fuel pump, driven by a permanent magnet electric motor mounted close to the fuel tank draws fuel from the tank and pumps it to the fuel rail via a fuel filter. The pump is of the 'wet' variety in that fuel actually flows through the pump and the electric motor. There is no actual fire risk because the fuel drawn through the pump is not in a combustible condition.
Mounted upon the armature shaft is an eccentric rotor holding a number of pockets arranged around the circumference - each pocket containing a metal roller. As the pump is actuated, the rollers are flung outwards by centrifugal force to act as seals. The fuel between the rollers is forced to the pump pressure outlet.
Fuel pressure in the fuel rail is maintained at a constant 2.5 bar by a fuel pressure regulator. The fuel pump normally provides much more fuel than is required, and surplus fuel is thus returned to the fuel tank via a return pipe. In fact, a maximum fuel pressure in excess of 5 bar is possible in this system. To prevent pressure loss in the supply system, a non-return valve is provided in the fuel pump outlet. When the ignition is switched off, and the fuel pump ceases operation, pressure is thus maintained for some time.
Fuel pressure regulator
The pressure regulator is fitted on the outlet side of the fuel rail and maintains an even pressure of 2.5 bar in the fuel rail. The pressure regulator consists of two chambers separated by a diaphragm. The upper chamber contains a spring which exerts pressure upon the lower chamber and closes off the outlet diaphragm. Pressurised fuel flows into the lower chamber and this exerts pressure upon the diaphragm. Once the pressure exceeds 2.5 bar, the outlet diaphragm is opened and excess fuel flows back to the fuel tank via a return line.
A vacuum hose connects the upper chamber to the inlet manifold so that variations in inlet manifold pressure will not affect the amount of fuel injected. This means that the pressure in the rail is always at a constant pressure above the pressure in the inlet manifold. The quantity of injected fuel thus depends solely on injector opening time, as determined by the ECU, and not on a variable fuel pressure.
At idle speed with the vacuum pipe disconnected, or with the engine stopped and the pump running, or at WOT the system fuel pressure will be approximately 2.5 bar. At idle speed (vacuum pipe connected), the fuel pressure will be approximately 0.5 bar under the system pressure.
Catalytic Converter and emission control
The Motronic injection system fitted to BMW vehicles equipped with a Catalytic Converter implements a closed loop control system so that exhaust emissions may be reduced. Closed loop systems are equipped with an oxygen sensor which monitors the exhaust gas for oxygen content. A low oxygen level in the exhaust signifies a rich mixture. A high oxygen level in the exhaust signifies a weak mixture. The Oxygen Sensor closed loop voltage is quite low and switches between 100 mVolts (weak) to 1.0 volt (rich).
The signal actually takes the form of a switch and switches from weak to rich at the rate of approximately 1 HZ. A digital voltmeter connected to the signal wire, would display.an average voltage of approximately 0.45 volts. In the event of OS circuit failure, the ECU substitutes a constant voltage of 0.45 volts and this should not be confused with the average voltage of 0.45 which occurs during switching from approximately 1.0 volt to 0.1 volt.
When the engine is operating under closed loop control, the OS signal causes the ECU to modify the injector pulse so that the AFR is maintained close to the stoichiometric ratio. By controlling the injection pulse, during most operating conditions, so that the air/ fuel ratio is always in a small window around the Lambda point (ie Lambda = 0.98 to 1.04), almost perfect combustion is achieved. Thus the Catalyst has less work to do and it will last longer with fewer emissions at the tail pipe.
The closed loop control is implemented during engine operation at engine normal operating temperature. When the coolant temperatures is below 70° C, or the engine is at full load or is on the overrun the ECU will operate in open loop. When operating in open loop, the ECU allows a richer or leaner AFR than the stoichiometric ratio. This prevents engine hesitation, for example, during acceleration with a wide open throttle.
The OS only produces a signal when the exhaust gas, has reached a minimum temperature of approximately 300° C. In order that the OS will reach optimum operating temperature as quickly as possible after the engine has started, the OS contains a heating element. The OS heater is controlled by the ECU through an OS relay or from the fuel pump relay depending on vehicle. The ECU switches off the OS relay under certain conditions of speed and load.
CFSV
A CFSV and activated carbon canister is employed to aid evaporative emission control. The carbon canister stores fuel vapours until the CFSV is opened by Motronic under certain operating conditions. Once the CFSV is actuated by the EMS, fuel vapours are drawn into the inlet manifold to be burnt by the engine during normal combustion.
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Sunday, 6 February 2022
E30 318i: Replacing Clutch Slave-Cylinder - Quick + dirty guide!
Clutch reservoir suddenly low on fluid? Gearbox housing covered in it? Sounds like a popped slave-cylinder. Not to worry, this has to be one of the easiest to replace ever made!
* This guide covers the M40 engine and 5-speed gearbox, but process is the same for most models. *
1. Lift the left side of the car.
2. Remove the 13mm nut from the outer side of the slave-cylinder. This one is easy to access and can be got with a ring-spanner or socket, but the ratchet is quite snug to the gearbox.
3. Remove the 13mm nut from the inner side of the slave-cylinder. This is quite difficult to get to as it is inhibited by the clutch-hose as well as limited access in the trans.-tunnel. I managed it with a socket and a 4" extension bar to get past the hose/pipe.
* I have seen someone getting that difficult to reach nut using a longer extension bar and the ratchet further back behind the gearbox, but this was not possible on my E30, so I'm guessing this may be for 4-speed boxes or older M10/M20 engines. If yours cannot be got with the details in step 3, then try this. *
4. Remove the slave-cylinder fr the gearbox and allow to hang down on the hose.
5. Clamp the hose (optional, but saves time when bleeding system later).
6. Remove the hose end from the slave-cylinder using an 11mm wrench so the old unit can be discarded. [It is much easier to grip the slave-cyl. by hand while it is removed from the gearbox and get a turn on the pipe-collar, as well as minimising leaks from the hose.]
7. Prime the new slave-cylinder by removing the bleed-nipple and carefully pouring DOT4 brake/clutch fluid into the hole at the top for the hose/pipe until the air is displaced and the fluid run out of the lower hole. It won't need much. Refit and tighten the bleed-nipple.
8. Refit the hose-end to the slave-cylinder and remove the hose-clamp if you're using one.
9. Refit the slave-cylinder to the gearbox and tighten the two 13mm nuts.
10. Top up the clutch reservoir with DOT4 brake/clutch fluid and bleed the system of air. [Which bleeding technique you use is up to you, but for all BMW clutches I would recommend using a one-way valve attached to the bleed nipple as detailed in THIS POST, which saves time and headaches.]
E30 316i / 318i Electrical Troubleshooting Manual [1984 onwards] - PDF 8.9MB
CONTENTS:
- Index
- How to Use this Manual
- Symbols
- Wire Size Conversion Chart
- Systematic Troubleshooting
- Diagnostic Connector
- Power Distribution Box
- Fuse Data
- Schematic Diagrams
- Component Charts and Figures
Friday, 17 December 2021
BMW E30 / E28 Diagnostic Plug / Socket Pin Out Diagram
| PIN: | WIRE SIZE: | WIRE COLOR: | APPLICATION: |
| 1 | 1.5 | Brown | Ground Distribution G101 |
| 4 | 0.5 | Brown / Violet | Gauges / Warning Indicators, |
| Coolant Temperature Sender | |||
| 5 | 0.5 | White / Green | Fuel Control, |
| Injector Control Module (Fuel Rate) | |||
| 7 | 0.5 | White / Blue | Service Indicator, |
| Service Interval Processor (Reset) | |||
| 11 | 2.5 | Black / Yellow | Start, Start Signal |
| 12 | 0.75 | Blue | Charge System, Alternator, |
| 13 | 0.75 | Black | Ignition, Ignition Coil |
| 14 | 2.5 | Red | Charge System, Alternator |
| 15 | 1.5 | Green / Yellow | Idle Speed Control, |
| Idle Speed Control Unit |
Sunday, 5 September 2021
E46 318i Touring: Replacing leaky Oil Cooler gasket [N42]
After fixing the major oil leak from the rocker-cover gasket [THIS POST], I noticed there was still some oil pooling on the under-tray and a fews spots dripping onto the road. I traced the source up the right side of the engine (looking from the front) and could see oil filling up some cavities in the cylinder-head to the left of the oil-cooler / filter housing, so determined this to be the culprit... yes, another common one, especially if the filter-housing has been removed for previous engine work.
4. Remove the three screws holding the oil-filter / cooler housing to the cylinder-head using a 10mm socket with a long extension bar. One is clearly visible in front of the housing, the other two being hidden down the back.
A replacement gasket was just £6.59 from eBay and comes as a two piece set including the main gasket that sits between the housing and the cylinder-head, as well as a smaller gasket that sits between the oil-filter housing and the coolant fed heat-exchanger. This latter one hardly ever leaks, as it's very rare to find a filter-housing that has been split apart during engine work, but it's nice to have one anyway and you may find it worth the time to replace this one while the housing is removed, though I could not see any signs of leakage so didn't bother.
GUIDE:
1. Remove the lid to the air-con ducting that sits atop the firewall at the back of the engine by undoing the clips a quarter-turn, take out the pollen-filter and remove the weather-strip seal from the firewall.
2. Remove the air-con ducting itself by undoing the four screws using a T30-Torx socket and lifting it out.
3. Remove the rear right-side engine cover by undoing the two stud-nuts using a 10mm wrench.\
** Make sure you have a cloth / plenty of tissue to catch any oil that runs from the housing. **
5. Lift the oil-filter / cooler housing upwards out of the head, catching any wayward oil and lift the housing clear, rotating it so as not to put too much strain on the coolant-hoses. The hoses do not need removing or any coolant draining for this job.
6. Remove the old gasket and clean both mating surfaces with a cloth and I find it always worth scraping any crud off with a razor-blade.
7. Insert the new gasket to the housing. A lug on one side sits in a notch in the housing so the gasket can only fit in one way. [If it's an older engine or the housing has been removed a few times before, it might be worth taking a belts-and-braces approach by applying some gasket sealant to the mating surface on the head, as I did with some white Corteco.]
8. Carefully place the filter/cooler housing back onto the cylinder-head, trying to spill as little oil as possible on the mating surface and reverse steps 4-1 to refit.
Monday, 26 July 2021
E30 M40 316i / 318i: Adjusting Throttle-Body and Idle Stop-Screw
Yes, this is set at the factory and they say it should never be messed with, but as the youngest M40 engined BMWs are approaching 30 years old now, chances are the stop-screw and throttle-plate will have been adjusted at some point in its life.
Here I will explain what happens when it is adjusted, the problems it may cause if it has been and how to reset it back to stock.
WHY HAS IT BEEN ADJUSTED?
The stop-screw should have a paint mark on it from the factory to show if it has been messed with, but after so many years the mark may no longer be visible. If you feel yours has been adjusted in the past, the main reason this has been done is likely to falsely raise a low idle caused by another issue, say an induction air leak. If an over lean mixture is causing a low idle, the tendency is to tweak the idle stop-screw to get the car to tick over at higher revs and stop the engine stalling out or running lumpy. This is a great short-term workaround, but will cause other issues with the AFM / DME and fuel delivery further down the line, particularly when the underlying issue is worked out.
SYMPTOMS:
The issues you will get with a poorly adjusted throttle stop-screw are:
High idle.
Hunting / pulsing revs.
Poor or no low-end throttle response.
Erratic idle (if throttle position switch TPS is not engaged).
Bogging at high revs (where wide-open throttle WOT switch is not engaged).
There is only one way the throttle can be adjusted, via the stop-screw, though the throttle-cable itself can be adjusted to change throttle response somewhat, mainly with how the pedal / cable reacts to driver input and will not affect the fuel/air ratio and the engine idle.
** The intended job of the idle stop-screw is simply to stop the throttle-plate from jamming in the throttle-body and being difficult to open when the pedal is pressed and not to change the car’s idle characteristics. BMW recommend that this is never played with, so do so at your own risk. **
1. Back off the lock-but using an 8mm wrench.
2. Use a small flat screwdriver to wind the idle stop-screw in and out.
* Clockwise will push the throttle-linkage further from its rest position, holding the throttle-plate open slightly and allowing more air to bypass it while the pedal is not pressed.
*Anti-clockwise will allow the throttle-linkage to close further and will reduce bypass air and choke the engine while the pedal is not pressed.
STOCK SETTING:
You will need a set of A/F / imperial feeler-gauges as this is how the stock throttle-plate aperture is measured.
** If you are only adjusting the throttle-plate and do not need to adjust the throttle position switch (TPS) then the throttle-body itself does not need removing and you can skip to step 7.**
Removing the Trottle-Body:
1. Remove the main air-inlet hose from the AFM to the throttle-body by loosening the jubilee-clip and easing it off.
2. Unclip the throttle-cable from the throttle-linkage and remove the two screws holding the throttle-cable mount from the top of the throttle-body housing using a 10mm wrench. Move the cable assembly to one side.
3. Remove the two water hoses and air vacuum-hose from either side of the throttle-body by undoing the jubilee clips and teasing the hoses off with a screwdriver.
4. Remove the six nuts from the upper inlet-manifold using an 11mm wrench and the two locating screws from the manifold using a 10mm wrench. Lift the upper inlet-manifold so that the throttle body can be fully accessed.
5. Remove the throttle-body from the inlet manifold by undoing the four nuts using a 10mm wrench.
7. Back off the lock-nut of the stop-screw using an 8mm wrench.
8. Use a small flat screwdriver to adjust the throttle stop-screw by the notch in the end of it. Obviously, clockwise will move the screw further out and make the throttle-butterfly rest in a more open position. Anticlockwise will allow the butterfly to close more.
9. For the OEM setting, the throttle-butterfly should be 0.377” from the housing, so use your feeler-gauge between the side of the tube and either side of the butterfly until you find a happy medium.
10. Tighten the lock-nut up again with an 8mm wrench.
11. Now take the throttle-position switch (TPS) and locate it back in the housing so that the switch is depressed while the throttle is in the fully closed position. With the two screws loosened, the TPS can be swivelled left and right as in pic below to adjust the point at which it engages. The ideal placement for the switch is to have it click closed while the throttle is open about 1mm. (You will hear the quiet click from the TPS as it opens and closes.) When you’re happy with the TPS placement tighten the screws to lock it in place.
13. Refitting is a reversal of steps 5-1.
Wednesday, 9 June 2021
E30 318i M40: GUIDE - Replacing lower inlet-manifold gasket - rough idle and stalling fixed!
The engine just about ticked over when warm, albeit with a slight misfire. On cold startups however, the misfire was a lot more severe and at low revs the engine just couldn’t hold on, stalling out due to a way over-lean mixture. It would drive though, but there was no throttle response until about halfway up the rev range and power would arrive with a bang. It is amazing how sensitive these older engines with analog electronics are to unmetered air leaks!
IF YOU HAVE THESE SYMPTOMS, CHECK HERE!
I ordered a new gasket from eBay, it was a snip at £6.88. Be careful when ordering, older M10 engine gaskets are far more plentiful, so ensure yours is the right one for the M40... they have a funny shape which is quite distinctive. Choice was limited, in fact I could find one more gasket for sale of the right type and that came with a full £30 set including a head gasket, so be sure to check out carpartsinmotion, they have rare-fit stuff.
GUIDE:
1. Undo the jubilee-clip and disconnect the large rubber duct from the throttle-body using a flat screwdriver or 7mm socket.
2. Unclip the throttle-cable from the throttle-linkage and remove the two 10mm screws holding the metal plate to the throttle-body so the cable assembly can be moved clear.
3. Remove the wiring connectors from the throttle position sensor [TPS] and idle control valve [ICV].
4. Remove the rubber hose from the bottom of the ICV.
5. Remove the vacuum air hose from the front side of the throttle-body by undoing the jubilee-clip and teasing it off carefully with a flat screwdriver.
6. Remove the two coolant hoses from either side of the throttle-body by undoing the jubilee clips and teasing them off with a flat screwdriver.
7. Remove the six nuts from the upper inlet-manifold using an 11mm wrench [9 in diagram] and two locating studs in the centre with a 10mm wrench [13 in diagram].
8. The upper inlet-manifold can now be lifted out of the engine bay.
9. Remove the wiring connector from the fuel-rail / injectors.
11. Remove the five nuts holding the ports of the lower inlet-manifold to the head using an 11mm socket [4 in diagram].
12. Remove the two bracing bolts from the lower inlet-manifold using a 13mm socket. (They point towards the right side of the car) [11 in diagram].
13. The lower inlet manifold is now free to be removed. This can be a bit tricky as the rigid fuel pipes are routed through one of the gaps in the manifold ports. Also make a note of how the hoses to the throttle-body are routed through around the lower manifold, as it can be confusing once the upper manifold is bolted back in.
14. Clean off the mating surfaces of the cylinder head and the inlet manifold.
15. Carefully fit the new gasket to the studs on the head. It only fits one way round.
16. To refit reverse the above steps.
Saturday, 5 June 2021
E30 318i: Correct Temperature Sensor fitted (Brown Plug) + wiring/loom issue
The temperature gauge in the dash has not worked since I bought the E30, which was a little worrying on my 250 mile drive home, but the car does not overheat. Oh, it has some issues with the cooling-system, like the heater-matrix pipes fitted incorrectly and an air-lock at the back of the head, but hey it doesn't overheat. Still though, I thought it best to get the bottom of the faulty temp. gauge for peace of mind, particularly with summer coming / just about here.
MULTIMETER TESTING:
The temp. sensors can be easily tested with a multimeter set to 20k ohms resistance.
The Blue plug is a two-pin sensor, so test across both terminals with the multimeter and you are looking for a reading of 4-4.5k ohms for a working sensor. This sensor and plug can be accessed easily without removing any parts from the engine.
The Brown plug though will require removal of the lower inlet-manifold to access the sensor for testing or replacing. This is a single pin sensor, so place one probe of the meter to the terminal and the other to a ground-point in the engine bay or against the block/head. Expect a reading of between 1k and 1.5k ohms for a working sensor. To test the Brown plug sensor without removing any parts from the engine, you can apply the multimeter to Pin 4 of the C101 connector (main wiring loom plug in engine bay) which is easy enough to get at, or at Pin 26 of the blue connector to the right side of the instrument binnacle, though the binnacle will need removing to do this.
WRONG SENSOR / CONFUSING WIRING LOOM:
Upon inspection, the rear temp. sensor fitted to my E30 is black, not brown and has two terminals. The second pin means that the sensor body earths back to the loom and not through the block so, if the redundant earth wire in my loom is not connected to a ground-point then the sensor was open circuit. I guessed that someone had ordered a second Blue plug sensor by mistake and fitted that, but it turns out the part number doesn't match and the sensor is for a completely different model engine entirely. The reading from the multimeter was over 11k ohms, something like 7.5 times what it should be! That sensor was never going to work with the E30 temp. gauge circuit whether it was earthed or not.
I ordered the correct single-pin sensor with the brown base from mr-wiper on eBay, who also supplied my Bosch spark-plugs. It was only £7.69 delivered. My temp. gauge now works, but this may also be due in part to removal of an air-lock at the back of the head due to a heater-matrix problem so coolant is now flowing properly round the area of the sensor.
A BIT MORE ON WIRING LOOMS:
Brown / Violet, brown being the main colour, denotes that the power source provided from the temp. gauge circuit is earthing through this wire and does not need to be a closed circuit back to the gauge. The other wire is either not wired in to the loom or goes to a body-earth anyway, so earthing the sensor through the block will make no difference. This colour coding is the same for all wires in all BMW looms, I would imagine most cars are the same.
Sunday, 30 May 2021
BMW E30 Heater Matrix Hoses Configuration - Right and Wrong way round + how to bleed matrix / remove air-lock
My E30 had little or no hot air from the blower inside the cabin. I have heard it is common for the two hoses running to the heater matrix to be fitted back to front, so the flow of coolant through the core is reversed. This causes air locks and severely reduces the amount of coolant flowing through the heater matrix, thus no hot air.
The reason these hoses so often get fitted incorrectly is due to their location and the way they look when fitted. It appears obvious that the upper hose (back of cyl.-head to heater) goes to the upper stub on the heater-matrix and the lower hose (side of block to heater) goes to the lower stub on the matrix. The hoses look happier this way round, but the matrix and heater-valve are designed in such a way that flow is interrupted and causes the air-lock.
The correct way round is actually with the upper hose connected to the lower stub and the lower hose to the upper stub, which does of course appear to be back to front, but is essential for correct flow of coolant round the whole engine, not just the heater-core. The correct and incorrect hose configurations are shown in the pictures below.
RIGHT:
WRONG:
** This is not the normal air-bleeding process when refilling an empty system with coolant, this process is to bleed a system with the air-lock at the back of the head and / or the heater-matrix full of air. **
1. Ensure heater-matrix hoses are fitted the correct way round, if not swap them over. [You should notice if there is an air-lock that no coolant comes out of the hoses when removed from the matrix and the stubs appear dry].
2. Fully tighten the lower [inlet] hose.
3. Leave the upper hose disconnected from the matrix.
4. Remove the radiator bottle cap. Assuming the coolant level is up to the halfway / max. mark, there should be some gulps of air and the coolant level should drop slightly in the rad. bottle.
5. Cut the bottom off a 2-litre drinks bottle and fill it with water, holding your hand over the lid.
6. Dump the water from the drinks bottle into the radiator bottle, allowing the weight of water to push the remaining air though the system. Water should start to come out of the upper heater-matrix hose from the head. Block this hose with a finger.
7. Continue to top up the radiator bottle with water until water begins to flow out of the upper stub on the heater matrix and quickly refit the upper hose, which can now be fully tightened.
8. Drain the radiator bottle back down the halfway /max. / fill line.
** You should be good to go, but can now bleed / top-up the system using the usual bleeding procedure if necessary. **
Wednesday, 26 May 2021
BMW M40 Engine - how to check timing, where the marks are located
This must be one of the hardest bits of info to find in the whole world of BMW, but there is a great post on BMW Werks on how to do it [https://www.bimmerwerkz.com/threads/m40-motor-timing-info.59059/].
QUICK TIMING CHECK GUIDE:
** Only if crank pulley has NOT been separated from crankshaft! **
1. Remove the distributor / timing cover at the front of the engine.
2. Check the timing mark on the crank pulley. This is an arrow cast into the block which should line up with the sprocket tooth to the right of the gap in the teeth, as in pic below.
3. Check the timing mark on the camshaft pulley. This is a notch/line mark in the pulley and should line up with the right-angle notch in the cylinder head, as in pic below. If this looks good, your timing is fine.
Thanks again to xdrian on BMW Works for making these pics and sharing this secret!
Sunday, 25 April 2021
Causes of flat batteries on BMWs explained - Great guide!!
If you own an older BMW, no doubt you will have experienced your battery suddenly starting to go dead for no apparent reason. All modern BMWs have a ‘shut-down’ procedure after the ignition is turned off, things can be heard whirring and humming even after you’ve locked the car and this is the most common cause of your battery going dead over night with no warning, but there are others too...
Below is a great guide from Vlad at MCA Blog explaining the reasons BMW batteries go flat over night and where to check. It also details that bane of the BMW battery's life, the 'IBS' or Intelligent Battery Sensor fitted from the '90s on.
- Plugged in external devices
- Plugged in OBD-II scanner
- BMW Intelligent Battery Sensor
- The infamous ”hedgehog” (from the climate control panel)
- One of the electronics on your car drains too much power or does not go into sleep mode
- Faulty alternator
- Old battery
Friday, 19 March 2021
BMW MOST Bus - Troubleshooting Guide [Vlad on MCA]
Great guide to the BMW MOST Bus (Media Oriented Systems Transport), used in all BMWs with fibre-optic connectivity. It covers what it is and what it does, as well as troubleshooting a lot of associated problems with these complex systems. It is from Vlad at MCA.org and can be found here:
https://mca.electricmura.ro/en/blog-bmw-most-troubleshoot/
Sunday, 6 December 2020
BMW Bosch Fuel Injection System Trouble-Shooting Guide
| SYMPTOM: | PROBABLE CAUSE: |
| No cold start | Fuel-pump fault or clogged fuel-filter |
| Additional air-valve not opening correctly | |
| Start-valve not opening correctly | |
| Leak in fuel system | |
| Throttle-valve plate not opening correctly | |
| Temp.-sensor fault | |
| Diode-relay fault | |
| Poor hot start | As above then: |
| Leaking / faulty injector | |
| Heat/time switch fault | |
| Poor idle | Baffle-plate stop wrongly adjusted |
| Leak in Vacuum-system | |
| Fuel-filter clogged | |
| Mixture-adjustment incorrect | |
| Backfire from engine | Weak fuel mixture |
| Fuel pressure too low | |
| Starter-valve leaking | |
| Engine runs on after shut-off | Leaking / faulty injector |
| Stiff/stuck baffle-plate | |
| Stiff/stuck control-plunger | |
| Excessive fuel consumption | Control pressure too low |
| Starter-valve leaking | |
| Leak in fuel-system | |
| Fuel mixture too rich | |
| Heat/time switch fault | |
| Idle-speed too high | Control pressure incorrect |
| Additional air-valve stuck open | |
| Baffle-plate stop wrongly adjusted |
Detailed maintenance guide / diagrams in this post [L-Jetronic] - https://www.beemerlab.org/2020/03/bmw-bosch-l-jetronic-fuel-injection.html
Bosch K-Jetronic injection-system overview / diagram here - https://www.beemerlab.org/2019/11/e21e12e28-bosch-k-jetronic-fuel.html
Bosch L-Jetronic injection-system overview / diagram here - https://www.beemerlab.org/2019/11/e30e28e34-bosch-l-jetronic-fuel.html
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