Fuel Pump Relay

Fault symptom
Fuel pump relay not working

Action
1 Check the voltage supply to the engine control system
Unplug connector H33-1.
Connect the test lamp between H33-1, pin 30 and a safe grounding point.
Turn the ignition key to the "ST" position (+ 50). The test lamp should flash during starter motor cranking.
If the test lamp flashes, proceed to point 2.
If the test lamp does not flash, proceed to point 4.

2 Check the cable between connector H33-1 and H33-4
Conduct a continuity test on the cable assembly between connector H33-1, pin 30 and connector H33-4, pin 11.
The resistance should be < 1 Ohm.
If the resistance is incorrect, take action on the cable assembly.
If the resistance is correct, proceed to point 3.







3 Check the cable assembly to the engine control system
Conduct a continuity test on the cable assembly between connector H33-4, pin 11 and
- Trionic control module, pin 56.
- Motronic 2.10.2 control module, pin 3
- Motronic 2.8.1 control module, pin 3
depending on the engine alternative.
The resistance should be < 1 Ohm.
If the resistance is incorrect, take action on the cable assembly.
If the resistance is correct, continue fault diagnosis in Engine Management System, "Trionic"or "Motronic".

4 Check if the fuel pump relay is working
Refit connector H33-1 and H33-4.
Unplug the fuel pump relay.
Connect the test lamp in the fuel pump relay socket between pins 86 and 85.
Turn the ignition key to the ST position (+ 50).
The test lamp should flash during starter motor cranking.
If the test lamp flashes, continue fault diagnosis in Engine Management System, "Trionic"or "Motronic".
If the test lamp does not flash, proceed to point 5.

5 Check if the fuel pump relay is working
Connect the test lamp in the fuel pump relay socket between pin 85 and pin 30.
Turn the ignition key to the "ST" position (+ 50).
The test lamp should start to flash during starter motor cranking. If the test lamp flashes, continue fault diagnosis in Engine Management System, "Trionic" or "Motronic"
If the test lamp does not flash, proceed to point 6.







6 Check the cable assembly
Conduct a continuity test on the cable assembly between the fuel pump relay socket, pin 85 and connector H33-3, pin 29.
The resistance should be < 1 Ohm.
If the resistance is incorrect, take action on the cable assembly.
If the resistance is correct, proceed to point 7.

7 Check the cable assembly to the control module
Unplug the control module. Conduct a continuity test on the cable assembly between
- Connector H33-1, pin 30 and the control module, pin 21
- Connector H33-3, pin 29 and the control module, pin 9 The resistance should be < 1 Ohm.
If the resistance is incorrect, take action on the cable assembly.
If the resistance is correct, proceed to point 8.

8 Final test
Start the car and check to see if the fault symptom remains.
If the problem remains, proceed Before Control Module Replacement.