LH Fuel System 2.2 : T16 Lambda
LH Fuel System Diagrams:
LH Fuel System Components:
Locations of components
1 Battery
On the left-hand side of the engine compartment
7 Earthing point
on the left-hand wheel housing
22A Fuse board
Behind the access panel in the glove compartment
59 Two-pole connector
Two in the engine compartment at the windscreen wiper motor
One on the right-hand side of the engine compartment, at the intake manifold
One at the fuel pumps, under the luggage compartment floor
60 Single-pole connector
One at the Lambda sensor, on the engine manifold
One on the left-hand side of the engine compartment, at the bulkhead
65 Earthing point
Under the back seat
67 Six-pole connector
Two in the engine compartment, at the windscreen wiper motor
75 Distribution block
Forward of the battery
76 Switch for raising the engine idling speed, auto
Under the centre console, at the gear selector lever, in gear selector switch 239
101 Feed pump
In the fuel tank, under the luggage compartment floor
102 Fuel pump relay
In the electrical distribution box behind the glove compartment
103 Fuel pump
In the fuel tank, under the luggage compartment floor
122 Eight-pole connector
Two behind the combined instrument
136 Lambda sensor
On the engine manifold, at the turbocharger
144 Pressure switch
Under the facia, to the left of the steering column (behind the knee shield)
146 Ignition system amplifier
On the left-hand wheel housing, forward of the battery
147 Ignition pulse amplifier
In the electrical distribution box behind the glove compartment
156 Relay for the AC and ACC radiator fan
In the electrical distribution box, behind the glove compartment
159 Distribution terminal +15
In the electrical distribution box behind the glove compartment
200 Control unit, LH fuel system
On the left-hand side of the bulkhead between the engine compartment and the passenger compartment
201 Engine earthing point
At the engine lifting lug
202 Engine temperature transmitter
On the intake manifold flange, between cylinders 2 and 3
203 Throttle angle transmitter
On the intake manifold
204 Test connector
On the left-hand side of the engine compartment, on the bulkhead
205 Air mass meter
On the hose between the air cleaner and the turbocharger air intake
206 Injection valves
On the underside of the intake manifold
210 EDU trip computer
In the combined instrument
211 Earthing point
On the gearbox
229 Main relay (fuel injection system)
In the electrical distribution box behind the glove compartment
230 Distribution terminal +30
In the electrical distribution box behind the glove compartment
23 1Distribution terminal +54
In the electrical distribution box behind the glove compartment
257 Earthing point
On the alternator bracket
271 Lambda sensor preheater
On the engine manifold, at the turbo charger
272 Engine idling speed adjustment
In the centre of the intake manifold
285 Lambda sensor fuse
In the engine compartment, at the windscreen wiper motor
Operation
The engine is equipped with the Bosch type LH Jetronic fuel injection system. LH is the abbreviation for Luftmassenmesser Hitzdraht (Air mass meter with hot filament). The fuel injection system is controlled and monitored by control unit 200, which includes a microprocessor.
The system receives its positive supply from fuse 13 across distribution terminal +15 when the ignition switch is in the start or drive position, and a constant supply from terminal +30 to relays 229 and 102.
The system calculates and controls the opening times of electrically controlled fuel injection valves 206, on the basis of the data stored in the control unit and information received from various transmitters.
The ignition pulses from the ignition system sensed at ignition pulse amplifier 147 (1987)/ignition system amplifier 146 (1988) provide the control unit with information on the engine speed.
Throttle angle transmitter 203 provides information on the throttle angle, i.e. the load on the engine. The transmitter has two contact positions, i.e. 0° (idling speed) and greater than 72° throttle angles.
Temperature transmitter 202 is of Negative Temperature Coefficient (NTC) type and continuously supplies the control unit with information on the engine temperature. If the signal is lost, the control unit will simulate an engine temperature of +20°C.
Air mass meter 205 includes a platinum filament. The temperature of the filament is maintained constant at about 100°C above the temperature of the incoming air, regardless of the composition of the air and its flow rate.
The current necessary for maintaining the temperature of the filament constant is controlled by a bridge circuit and a measuring resistor, the voltage variation of which is directly proportional to the mass flow of the intake air.
Since the filament is located in the intake air path, it will gradually become fouled, which will affect the measurement results. To keep the filament clean, it is heated to about 1000°C for one second, to burn away any impurities collected on it. This will take place four seconds after the engine has been switched off, provided that its speed has previously been higher than 2000 r/min. This burning-off process is controlled by the control unit.
If the signal from the air mass meter should cease, e.g. due to failure of the filament, an emergency system, known as the Limp-home system, incorporated into the control unit will come into operation. This enables the car to be driven, although at impaired performance.
Fuel is supplied to the engine by electrically driven fuel pump 103 and feed pump 101 which draws fuel from the fuel tank and pressurizes the fuel in the system. The fuel pump circuit includes pressure switch 144 which will shut off the pumps if the boost pressure from the turbocharger should exceed a predetermined limit.
Valve 272 for automatic idling speed control is controlled by the control unit and can by-pass a sufficient amount of air across the throttle to keep the engine running at the required idling speed.
The control unit is also connected to EDU2 trip computer 210 and the air conditioning system (AC relay 156).
Test tapping 204 has terminals for checking the following signals:
1. Positive voltage to the fuel injection valves/fuel pump
2. "Limp-home" signal
3. Pulse relationship, Lambda
- Automatic Idle Control (AIC)
The control unit is connected to the air conditioning system via pin 16 of AC 156. When the AC compressor is operating and the car is idling, the control unit compensates for the resulting increase in load. The signal (earth) is supplied from pin 12 when the accelerator pedal is depressed fully.
Exhaust gas emission control (Lambda)
Cars delivered to the US, CA, JP and AU markets and SE and EU cars with catalytic converter include components for more sophisticated fuel control. Lambda sensor 136 is used to measure continuously the oxygen content of the exhaust gases, and the control unit can then adjust the fuel/air ratio to the optimum value. The sensor is heated by preheater 271, supplied across a separate in-cable fuse.
Automatic transmission
Cars with automatic transmission are equipped with switch 76, which closes when the selector lever is in the drive position, allowing the control unit to compensate for the increased load on the engine caused by the automatic transmission.
Cars with catalytic converter for the US, CA, JP AU, SE and EU markets are also equipped with a jumper between pins 11 and 15 of control unit 200.
Fault-tracing hints
Always bear in mind the following when carrying out fault-tracing in the wiring:
1. Always disconnect the 25-pole connector from the control unit and the connector on the air mass meter. NOTE: These two components can easily be seriously damaged if measurements are carried out at their terminal pins.
2. Always disconnect the electrical connection from the component which is suspected of being faulty.
3. Use an ohmmeter (not a buzzer) to carry out check measurements in the wiring.
The common earthing point (201) for the system is important for correct performance of the system. The location and connection must not be changed. The performance of the system may be disturbed if the location is altered, e.g. during other work on the engine.
For particulars of fault tracing and checking of individual electrical components in the system, see the Service Manual, Group 2:3, Fuel system, fuel injection.