Checking Fuel Pump (FP) Relay
Checking fuel pump (FP) relay
Fuel pump (FP)
- Ignition off.
- Remove fuse 1.
- Ignition on.
- Lightly squeeze the hose connected to the fuel pressure regulator and reinstall fuse 1.
- Check that the fuel pump works for a few seconds after the fuse is refitted. When the fuel pump (FP) is operating the fuel hose connected to the fuel pressure regulator pulses.
Note! If the pump does not work at the first attempt, repeat the process a couple of times to verify that the pump does not work.
Is the fuel pump (FP) working?
Yes - Fault-tracing information
No - Starting fuel pump (FP)
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Starting fuel pump (FP)
- Ignition off.
- Remove central electrical unit cover.
- Remove the fuel pump (FP) relay (pos. 103 in the electrical distribution unit).
- Ignition on.
- Connect a cable between relay base terminals 1 and 3.
The fuel pump should start.
OK - Checking fuel pump (FP) relay ground lead
Not OK - Fault-tracing information
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Checking fuel pump (FP) relay ground lead
- Ignition off.
- Fuel pump (FP) relay removed.
- Connect an ohmmeter between relay base terminal 2 and ground.
The ohmmeter should read approximately 0 ohms.
OK - Checking signal cable voltage
Not OK - Checking the fuel pump relay ground connector
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Fault-tracing information
The fuel pump (FP) relay is OK. Fault-trace the fuel pump (FP).
Continue - No Fault Found
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Checking the fuel pump relay ground connector
- Ignition off.
- Fuel pump (FP) relay removed.
- Check fuel pump (FP) relay ground terminal (31/51) for contact resistance and oxidation and remedy according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
- Connect an ohmmeter between relay base terminal 2 and ground.
The ohmmeter should read approximately 0 ohms.
OK - Fault-tracing information
Not OK - Checking for an open-circuit
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Fault-tracing information
The source of the fault is poor contact in the fuel pump relay ground connector.
Continue - FAULT FOUND
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Checking for an open-circuit
- Check cable between fuel pump (FP) relay terminal 2 and ground terminal (31/51) for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Verification
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Checking signal cable voltage
- Ignition on.
- Fuel pump (FP) relay removed.
- Connect a voltmeter between relay base terminal 4 and ground.
The voltmeter should read 4-5 V.
OK - Checking connector
Low - Checking signal cable resistance to ground
High - Checking for a short-circuit
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Checking for a short-circuit
- Check cable between fuel pump (FP) relay terminal 4 and engine control module (ECM) #B27 for a short-circuit to supply voltage according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Verification
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Checking signal cable resistance to ground
- Ignition off.
- Wait approximately 150 seconds.
- Fuel pump (FP) relay removed.
- Disconnect control module.
- Connect an ohmmeter between relay base terminal 4 and ground.
The ohmmeter should read infinite resistance.
OK - Breakout box
Not OK - Checking for a short-circuit
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Checking for a short-circuit
- Check cable between relay base terminal 4 and engine control module (ECM) #B27 for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Verification
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Breakout box
Connecting breakout box (connector B)
Connecting the breakout box
Is the breakout box connected to the Motronic 4.4 connector?
Yes - No Fault Found
No - Connecting breakout box to Motronic 4.4 connector B (gray)
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Connecting breakout box to Motronic 4.4 connector B (gray)
- Ignition off.
- Disconnect control module.
Note! The engine control module (ECM) must not be removed from the car until the main relay has interrupted its power supply. This may take up to 150 seconds (cars with an immobilizer 245 seconds) after the ignition has been switched off.
Connect adapter 951 1351 ADAPTOR 86-PIN 951 1351 Adaptor 86-Pin to engine control module (ECM) connector and connect breakout box 981 3190 Replaced by 9511428 981 3190 Replaced by 951 1428 to adapter.
Continue - Checking ground terminal #B28
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Checking ground terminal #B28
- Ignition off.
- Switch off all equipment that takes power from the battery (courtesy lighting, radio etc).
- Connect control module.
- Connect an ohmmeter between #28 (#B28) on the breakout box and battery negative terminal.
The ohmmeter should read approximately 0 ohms.
OK - Reading is OK
Not OK - Checking for an open-circuit
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Checking for an open-circuit
- check ground terminals 31/32 and 31/33 on the engine and their cables for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault and contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - No Fault Found
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Reading is OK
- Return to the fault-tracing procedure where it was interrupted.
Continue - No Fault Found
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FAULT FOUND - Checking signal cable resistance
No Fault Found - Checking signal cable resistance
FAULT-TRACING FAILED - Checking signal cable resistance
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Checking signal cable resistance
- Ignition off.
- Fuel pump (FP) relay removed.
- Connect an ohmmeter between the #27 (#B27) on the breakout box and relay base terminal 4.
The ohmmeter should read approximately 0 ohms.
OK - Checking connector
Not OK - Checking for a short-circuit
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Checking for a short-circuit
- Check cable between fuel pump (FP) relay terminal 4 and engine control module (ECM) #B27 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Verification
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Checking connector
- Ignition off.
- Reinstall the fuel pump relay.
- Connect control module.
- Try to start the engine.
Does the engine start?
Yes - Checking for contact resistance and oxidation
No - Replacing component
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Checking for contact resistance and oxidation
The cause of the fault has been loose connections in the control module or fuel pump (FP) relay connectors.
- Check connectors for contact resistance and oxidation and remedy in accordance with Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - FAULT FOUND
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Replacing component
- Try a new fuel pump (FP) relay.
Continue - Verification
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Verification
Verify
Verification
Hint: After repair, it is necessary to check that the fault has been corrected. Perform as follows:
- Switch off ignition.
- Reconnect connectors, fuel pump relay etc.
- Remove fuse No. 1.
- Switch on ignition.
- Use fingers to lightly pinch hose connected to fuel pressure controller and reinstall fuse No. 1.
- By feeling hose check that pump runs for a few seconds after fuse has been inserted.
Note! If pump does not run at first attempt, repeat test once or twice to verify that pump is not operating.
Is pump running?
Yes - VERIFIED
No - VERIFICATION FAILED
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VERIFIED - FAULT FOUND
VERIFICATION FAILED - Fault-tracing information
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Fault-tracing information
Information
Fault-tracing information
The fault should be diagnosed and remedied. Since this is not the case the fault-tracing process has failed.
Complete the fault-tracing for those fault or try again.
Do you want to terminate fault-tracing at this time?
Yes - Exit fault-tracing
No - Attempt New Test
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Fault-tracing information
Information
Fault-tracing information
The result shows that you cannot proceed with this diagnostic procedure.
Continue - No Fault Found
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No Fault Found - No Fault Found
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