LH 2.4 Fuel System; T16/I16 Lambda
LH 2.4 Fuel System Components:
LH 2.4 Fuel System Diagrams:
Locations of components
1 Battery
On the right-hand side of the engine compartment
7 Earthing point
On the radiator cross-member
9 Earthing point
In the luggage compartment
22A Fuse holder
In the electrical distribution box in the engine compartment, on the left-hand wheel housing
31 Reversing light switch
Under the centre console, at the selector lever
47K SHIFT UP warning lamp
In the combined instrument in the instrument panel
47P CHECK ENGINE warning lamp
In the combined instrument in the instrument panel
57 3-pole connector
(322) At the control unit, forward of the right-hand front door, below the fascia (behind the trim)
59 2-pole connector
One at the fuel pump, under the luggage compartment floor (1989 model)
(368) One at the control unit, forward the right-hand front door, below the fascia (behind the trim)
One (for the Lambda sensor) in the engine compartment, on the right-hand wheel housing, next to the distribution block for the positive supply from the battery
60 Single-pole connector
One (for the Lambda sensor) in the engine compartment, on the right-hand wheel housing, next to the distribution block for the positive supply from the battery
One (for the automatic transmission) at the control unit, forward of the right-hand front door, below the fascia (behind the trim)
One in the electrical distribution box
One on the right-hand side of the engine compartment, at the air intake (1990 model)
67 6-pole connector
Two in the engine compartment, on the right-hand side at the air intake
75 Distribution block, positive supply from battery
In the engine compartment, on the right hand side
76 Switch for raising the idling speed, auto. trans.
Under the centre console, at the selector lever
94 Cold starting valve
On the engine throttle housing
101 Fuel feed pump (1989 model)
In the fuel tank, under the luggage compartment floor
102 Fuel pump relay
At the control unit, forward of the right-hand front door, below the fascia (behind the trim)
103 Fuel pump (1989 model)
In the fuel tank, under the luggage compartment floor 76
123 4-pole connector
At the control unit, forward of the right-hand front door, below the fascia (behind the trim) one at the fuel pump, below the luggage compartment floor (1990 model)
132 Speed transmitter
On the rear of the combined instrument
136 Lambda sensor
On the exhaust manifold
152A 29-pole white connector
152B 29-pole red connector
In the electrical distribution box in the engine compartment, on the left-hand wheel housing. The connectors are accessible from the interior of the car
156 Relay for the AC compressor
In the electrical distribution box in the engine compartment, on the left-hand wheel housing
159 Distribution terminal +15
In the electrical distribution box, in the engine compartment, on the left-hand wheel housing
176 Control unit for EZK ignition system
In the engine compartment, forward of the left-hand wheel housing
200 Control unit for the LH system
Forward of the right-hand front door, below the fascia (behind the trim)
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 engine throttle housing
205 Air mass meter
On the air hose at the air cleaner
206 Fuel injection valves
On the engine intake manifold
211 Earthing point
On the gearbox
229 Main relay for the fuel injection system
Forward of the right-hand front door, below the fascia (behind the trim)
271 Preheater
In the Lambda sensor, on the exhaust manifold
272 Idling speed adjustment motor
At the extreme front, on the left-hand side of the cylinder head
321 Valve for charcoal cannister
In the engine compartment, forward of the left-hand wheel housing, between the wheel housing member and the outer wing
322 Connector, Auto/Man, LH 2.4
At the control unit, forward of the right-hand front door, below the fascia (behind the trim)
323 Fuel pump with integrated feed pump
In the fuel tank, below the luggage compartment floor
347 Test connector, diagnostics
On the right-hand side, under the back seat under the rubber bellows, behind the centre console (Convertible) under the bellows (Convertible)
368 Connector, cold-starting valve
At the control unit, forward of the right-hand front door, below the fascia (behind the trim)
389 NTC resistor
In the engine compartment, under the throttle housing (1990 model)
390 Modulating valve
In the engine compartment, forward of the left-hand wheel housing (1990 model)
Operation
Cars with 16-valve engines and Lambda are equipped with the Bosch LH Jetronic 2.4 fuel injection system, which is an updated version of the LH Jetronic 2.2 system. LH is an abbreviation of Luftmassenmesser Hitzdraht (air mass meter with hot filament). The fuel injection system is controlled and supervised by control unit 200, which includes a microprocessor.
A number of new features have been introduced, such as:
- Adaptive Lambda control system
- AIC (Automatic Idling Control) valve with built-in "Limp home" function. When necessary, the valve provides a high, fixed idling speed of approximately 1200 r/min.
- Adaptive idling control system. Normal changes are compensated for automatically. The idling speed is controlled by means of valve 272.
- Built-in deceleration function. During overrun braking, it shuts off the fuel supply within a certain engine speed range.
- A new, electrically-operated vent valve (321) for the charcoal canister. Controlled by signals from the control unit. The charcoal in the canister absorbs fuel fumes in the vent line from the tank.
- Built-in fault diagnosis system. Gives fault codes via the CHECK ENGINE lamp or the SAT test instrument.
- The pressure monitoring function is built into the control unit. If a fault should occur on the turbocharger pressure control system (T16 Lambda), the LH control unit will interrupt the signals to the injection valves.
- The gear indication function is built into the control unit (US only).
The system receives a positive supply from fuse 22 when the ignition switch is in the start or drive position, and a constant supply from +30 to relays 229 and 102.
On the basis of the data stored in the control unit and the incoming information from various sensors, the control unit calculates and controls the opening times of the electrically operated fuel injection valves (206). Control unit 200 receives information on the engine speed by sensing the pulses from the ignition system.
Throttle angle transmitter 203 provides information to the control unit on the throttle angle. The transmitter has two contact positions, i.e. 0° (idling speed) and 72° throttle angle.
Temperature transmitter 202 is of Negative Temperature Coefficient (NTC) type and provides continuous engine temperature information to the control unit. In the event of loss of this signal, the control unit will simulate, by default, an engine temperature of +45 °C (113 °F).
Air mass meter 205 is built into a plastic housing. In the event of a loss of signal from the air mass meter, e.g. if the filament should fail, an emergency system known as the "Limp home" function in the control unit will come into operation. The car can then be driven, although its driveablity will be limited. When the "Limp home" function is operative, warning lamp 47P, CHECK ENGINE, will light up. The lamp is located in the combined instrument, and is supplied from fuse 7. (The lamp can also be energized from the EZK ignition system.)
If a fault affecting the exhaust emissions should occur, the CHECK ENGINE lamp will light up.
The engine is supplied with fuel either by electrically driven fuel pump 103 and feed pump 101 or by fuel pump 323 with integrated feed pump. In both cases, the pumps draw fuel from the fuel tank and pressurizes the fuel system.
The control unit 200 is connected to the air-conditioning system via pin 14 (AC compressor relay 156, pin 16). When the AC compressor is running, the control unit will compensate for the increased load applied by the compressor at engine idling speed. A signal (earth) is applied from pin 3 at full throttle, which disconnects the AC compressor.
Test connector 347 is used for fault-tracing. When pin 2 in the connector is earthed, flashing codes will be obtained on the CHECK ENGINE lamp.
Exhaust gas emission control, Lambda
The car is equipped with an adaptive Lambda system, which compensates for variations in the fuel/air mixture caused by changes in the fuel system.
Lambda sensor 136 continually measures the oxygen content of the exhaust gases, thus enabling the control unit to adjust the mixture to as close to Lambda = 1 as possible. The sensor is heated by preheater 271 (protected by fuse 1).
Automatic transmission
Cars with automatic transmission are also equipped with switch 76 which will close when the selector lever is set to "Drive", and the control unit will then compensate for the increased load applied by the automatic transmission when the engine is running at idling speed.
Fault-tracing hints
When fault tracing in the wiring for the fuel system, always observe the following:
1. Read the fault codes that have been stored before disconnecting the control unit. (The fault codes are erased when the control unit is de-energized.) Use a test cable or the ISAT.
2. Always disconnect the 35-pole connector on the control unit and the connector on the air mass meter. N.B. These two components can easily be seriously damaged if measurements are carried out on their terminal pins.
3. Always disconnect the connection to the suspected component.
4. Use an ohmmeter not a buzzer for checking the wiring.
Before checking the wiring, always start by checking fuse 22 and checking that the supply to it is live. Also check fuse 7 and fuse 1 for the Lambda sensor preheater.
Earthing point 201 on the engine lifting lug is important for correct operation of the fuel system. If the location of the earthing point is altered, such as when other work is being carried out on the engine, the performance of the system may be disturbed.