Test Point

Alternator/Regulator

Peak voltage of the alternator could cause engine misfiring.

2. Start engine. If misfiring is eliminated, check alternator and regulator.

1. Remove drive belt and alternator.

If pressure rises to less than 4 bar, check fuel filter or, if necessary, replace fuel pump.

5. If engine cannot be operated, pull off relay XVII and bridge terminals 30 and 87.

Fuel pump must run. Specification: 2.3 . . . 2.7 bar.

TESTING OXYGEN SENSOR OPERATION, UP TO '86 MODELS

Brief test

If CO value does not change, there is a fault in either the oxygen sensor or the LH control unit.

Precondition:

- Engine at operating temperature.

- Ideal speed correctly adjusted.

- Exhaust tester connected to extraction point in engine compartment.

1.Disconnect oxygen sensor plug, wait until state of equilibrium is reached and note CO value.

Testing sensor voltage

¡.Precondition as for the "brief test"

2.Disconnect oxygen sensor plug.

3.Connect voltmeter to sensor half of plug and earth

2.Disconnect vacuum line from fuel pressure regulator.

The CO reading must show a considerable increase.

3.Reconnect oxygen sensor plug. The CO value must return to the specified 0.6 + 0.2%.

4.The voltage must be in the 0.1 V - 1.0 V range (depending on level of oxygen in the exhaust).

Voltage characteristic of oxygen sensor for working temperature of 600°C.

Rich mixture Lean mixture (air deficiency) (excessive air)

Printed in Germany - XVI, 1987 Testing Oxygen Sensor Operation 24 - 120 a

Testing lambda control function l.Test precondition as for "brief test".

2.Disconnect oxygen sensor plug.

3.With a length of cable, briefly connect cable of control-unit side of plug to ground.

The CO value must increase.

If there is no change in the CO value check connection to LH control unit, if necessary replace control unit.

24 - 120 b Testing Oxygen Sensor Operation

Printed in Germany

TESTING AND ADJUSTING SPECIFICATIONS FOR LH-JETRONIC — TYPE 928 S Rest of World

Beginning with 1984 Models Engine Type M 28.21/22

Test Point

Specifications

Remarks

Electric fuel pump Delivery rate

at least 1350 cc/30 sec.

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