Fuel Pump Relay: Testing and Inspection

Testing fuel pump relay module

Test Data:

Module Connector Pin Assignments:

Test

Key To Symbols:

Notes:
- If the specified value of a test step, e.g. step 4.0, is in order, it is not necessary to perform test step 4.1.
- Different component designations are possible depending on wiring diagram or in the case of vehicles with optional equipment.
These designations are given in parentheses. The fuel pump relay module has been designated uniformly with N16/4 (N5/1, N5/2, N16/1, N16/2, N16/3 also possible in the wiring diagrams).

Test Steps 1.0 - 1.4:

Test Steps 1.5 - 4.0:

Step Test 5.0:

Special Tool:

Commercially Available Testers:

Function
The fuel pump relay performs the following functions:
^ Brief supply of voltage to fuel pump when ignition is on.
^ Voltage supply to fuel pumps when engine started and when running.
With KAT, additionally voltage supply of oxygen sensor heater.
Voltage supply of auxiliary air valve (only vehicles without idle speed control).
^ Shuts off fuel pumps when maximum engine speed is reached (speed limiter versions see table).
^ Switches off fuel pump as soon as no further pulses supplied vie terminal TD of ignition control module.
^ Kick down shutoff.
^ Starting valve actuation. Testing and Inspection
^ As of 09/89 the function in the fuel pump relay module is partially supplemented in two stages by a separate oxygen sensor heater:




1st version up to approx. 12/89
The fuel pump relay module is fitted with an additional connector for the oxygen sensor heater with the designation 87H. This also results in a modification to the cable assignment at the relay module.
The actuation is performed as before as the additional connector 87H is linked by a bridge to the connector with the designation 87.




2nd version as of 01/90
From this date on the fuel pump relay module is no longer equipped with a bridge between terminals 87 and 87H. The electronic circuitry in the relay is modified as a result. The cut-in temperature for the oxygen sensor heater is + 20°C and is determined by the coolant temperature sensor.

Note: Only the new fuel pump relay modules are available through replacement parts. This means that in vehicles prior to 09/89, the actuation of the fuel pump and oxygen sensor heater continues to be performed by connector 87. Connector 87H on these vehicles does not perform any function.

Arrangement of fuel pump relay module



The fuel pump relay module is located on the right of the component compartment.

Exception: engine 102.951 in model 201. Fuel pump relay in front of electrical center (see ill.).