Refer to
Fuel Controls
in Engine Controls Schematics.
Circuit Description
When the ignition switch is turned ON, the VCM enrgizes the fuel pump relay which powers the in-tank fuel pump ON. The in-tank fuel pump remains ON as long as the engine is cranking or running and the VCM is receiving the distributor reference pulses. If there are no reference pulses, the VCM shuts the fuel pump OFF within 2 seconds after the ignition was turned ON or if the engine stops. The VCM will also turn ON the fuel pump for 2 seconds when the ignition is turned to the OFF position.
Diagnostic Aids
If the fuel pump relay circuit checks out OK, refer to Fuel System Diagnosis .
Excessive fuel may also cause long cranking times which is accompanied by the following conditions:
| • | A start that is not as fast as normal. |
| • | A puff of black smoke at the tailpipe. |
An improperly connected or faulty EVAP canister component can cause this problem. Disconnect the EVAP purge hose from the EVAP canister control valve in order to diagnose. Refer to Evaporative Emission Control System Diagnosis .
One or more leaking SFI injectors may also extend the cranking time. Perform the Injector Balance Test. Refer to Fuel Injector Balance Test with Tech 2 .
Test Description
Number(s) below refer to step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and stores the freeze frame and failure records data on the scan tool, if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.
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If the no start condition was due to a open fuse, locate and repair any shorts that may have caused the fuse to open before replacement.
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This step determines if the fuel pump circuit can be controlled by the VCM. The VCM should energize the fuel pump relay and turn the fuel pump ON when commanded by the scan tool. If the engine is not cranking or running, the VCM should de-energize the relay and turn OFF the fuel pump after 2 seconds.
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Jumpering the fuel pump positive voltage terminal to the fuel pump relay ignition positive voltage terminal verifies that the fuel pump relay ignition positive voltage circuit, the fuel pump positive voltage circuit, the fuel pump and fuel ground are all OK.
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This step checks for an open ground circuit.
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Replacement VCMs must be reprogrammed. Refer to the latest Techline information for programming procedures.
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This step checks the fuel pump ground circuit on the fuel sender side of the body harness connector only. If the fuel pump ground circuit is OK, then the fuel pump positive voltage circuit or the fuel pump ground circuit in the fuel tank harness or the fuel pump itself is malfunctioning.
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This test will determine if a short to ground on the fuel pump positive voltage circuit caused the fuse to open. To prevent mis-diagnosis, be sure the fuel pump harness is disconnected before the test.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
2 | Does the fuel pump run continuously with the ignition key OFF? | -- | ||
Inspect the fuel pump relay fuse. Is the fuse OK? | -- | |||
Does the in-tank fuel pump run when commanded ON? | -- | |||
Does the fuel pump run? | -- | |||
6 |
Is the test lamp ON? | -- | ||
7 | With a test lamp connected to ground, probe the ignition positive voltage terminal to the fuel pump relay. Is the test lamp ON? | -- | ||
With a test lamp connected to B+, probe the ground terminal to the fuel pump relay. Is the test lamp ON? | -- | |||
9 | Check for an open or short to ground in the fuel pump control circuit and repair as necessary. Was a repair necessary? | -- | ||
10 |
Is the test lamp ON? | -- | ||
11 | Repair the open in the ignition positive voltage circuit for the fuel pump relay. Is the action complete? | -- | -- | |
12 | Replace the fuel pump relay. Refer to Fuel Pump Relay Replacement . Is the action complete? | -- | -- | |
13 | Repair the open ground circuit to the fuel pump relay. Is the action complete? | -- | -- | |
14 | Inspect connections and terminals at the VCM and repair as necessary. Was a repair necessary? | -- | ||
15 | With a test lamp connected to B+, probe the fuel pump ground circuit (body harness side). Is the test lamp ON? | -- | ||
16 | Repair the open or short to ground in the fuel pump positive voltage circuit. Is the action complete? | -- | -- | |
Is the action complete? | -- | -- | ||
Check the fuel pump positive voltage and ground circuits at the body connector (tank side) for an open. Repair the circuit as necessary, refer to Connector Repairs in Wiring Systems. Was a repair necessary? | -- | |||
19 | Repair the open fuel pump ground circuit. Is the action complete? | -- | -- | |
20 | Before replacing the fuel sender, refer to Intermittents and Poor Connections Diagnosis Replace the fuel sender assembly. Refer to Fuel Sender Assembly Replacement . Is the action complete? | -- | -- | |
|
Caution: The fuel pump will operate for 2 seconds after you have turned off the ignition. Make sure that all the fuel pipes and fittings are securely fastened in order to prevent personal injury.
Is the test lamp ON? | -- | |||
22 | Repair the short to ground in the fuel pump positive voltage circuit. Is the action complete? | -- | -- | |
23 | With the test lamp still connected to B+, probe the fuel pump relay ignition positive voltage circuit terminal. Is the test lamp ON? | -- | ||
24 | Repair the short to ground in the fuel pump relay ignition positive voltage circuit. Is the action complete? | -- | -- | |
25 | Check the fuel pump positive voltage circuit in the fuel pump harness (tank side) for a short to ground and repair as necessary. Was a repair necessary? | -- | ||
26 | Disconnect the fuel pump relay. Does the fuel pump continue to run? | -- | ||
27 | With a test lamp connected to ground, probe the fuel pump relay control cavity with the ignition key in the OFF position. Is the test lamp ON? | -- | ||
28 | Replace the fuel pump relay. Refer to Fuel Pump Relay Replacement Is the action complete? | -- | -- | |
29 | Check for a short to voltage on the fuel pump relay control line. Was a repair necessary? | -- | -- | |
30 | Check for a short to voltage on the fuel pump positive voltage line from the fuel pump relay to the fuel pump. Was a repair necessary? | -- | -- | |
31 |
Does the engine start and continue to run? | -- | ||
32 |
Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
