Circuit Diagnosis - Fuel Pump Relay

CIRCUIT DESCRIPTION
When the ignition switch is turned ON, the VCM turns 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 is ON or the engine stops.

Should the fuel pump relay or the 12 volt relay drive from the VCM fail, the fuel pump receives a supply current through the oil pressure switch backup circuit. The fuel pump test terminal is located in the drivers side of the engine compartment. When the engine is stopped, applying the battery voltage to the test terminal can turn on the fuel pump.

DIAGNOSTIC AIDS
An inoperative fuel pump relay can result in long cranking times. The time necessary for the oil pressure to reach the pressure required in order to close the oil pressure switch and supply the necessary current for the fuel pump causes the extended crank period. If the fuel pump relay circuit checks out OK, refer to Fuel System Diagnosis. System Diagnosis - Fuel System

Excessive fuel may also cause long cranking times which is accompanied by the following conditions:
1. A start that is not as fast as normal.
2. A puff of black smoke at the tailpipe.

An improperly connected or faulty EVAP canister control valve can cause this problem. Disconnect the [1][2]EVAP purge hose from the EVAP canister control valve in order to diagnose. Refer to EVAP Control System Diagnosis. System Diagnosis - EVAP Control

One or more leaking poppet nozzles may also extend the cranking time. Perform the Poppet Nozzle Test, in the Injector Balance Test Table. Refer to Fuel Injector Balance Test. Fuel Injector Balance Test

TEST DESCRIPTION
Number(s) below refer to step number(s) on the Diagnostic Table.

1. 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.
3. 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.
4. 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.
5. Jumpering the fuel pump feed terminal to the fuel pump relay ignition feed terminal verifies that the fuel pump relay ignition feed circuit, the fuel pump feed circuit, the fuel pump and fuel ground are all OK.
8. This step checks for an open ground circuit.
17. Replacement VCMs must be reprogrammed. Refer to the latest Techline information for programming procedures.
18. 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 feed circuit or the fuel pump ground circuit in the fuel tank harness or the fuel pump itself is malfunctioning.
21. This test will determine if a short to ground on the fuel pump feed circuit caused the fuse to open. To prevent mis-diagnosis, be sure the fuel pump harness is disconnected before the test.before the test.