Symptom Related Diagnostic Procedures

Fuel Pump Circuit:

Circuit Description
When the ignition switch is turned "ON," the Powertrain Control Module (PCM) turns "ON" the in-tank fuel pump. The in-tank fuel pump will remain "ON" as long as the PCM is receiving ignition references pulses from the Ignition Control Module (ICM). If there are no references pulses, the PCM will shut "OFF' the fuel pump about 2-3 seconds after key "ON," or about 10 seconds after reference pulses stop. Whenever sufficient oil pressure is present to close the oil pressure switch, the fuel pump will remain "ON" during cranking without reference pulses.
The pump delivers fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure is controlled between 283-324 kPa (41-47 psi) with no manifold vacuum or between 214-303 kPa (31-44 psi) at idle. Excess fuel is then returned to the fuel tank.
Improper fuel system pressure will result in one or all of the following symptoms:
- Cranks but will not run.
- DTC P0171
- DTC P0172
- DTC P1171
- DTC P0300
- Cuts out, may feel like an ignition problem.
- Poor fuel economy, loss of power.
- Hesitation.

Diagnostic Aids
A failed pump relay will result in extended engine crank time because of the time required to build enough oil pressure to close the oil pressure switch and turn "ON" the fuel pump. There may be instances when the relay has failed but the engine will not crank fast enough to build enough oil pressure to close the switch. This or a faulty oil pressure switch can result in an "Engine Cranks But Will Not Run" condition.

Table A-5 - Engine Cranks But Will Not Run (Fuel Pump Circuit) (1 Of 3):

Table A-5 - Engine Cranks But Will Not Run (Fuel Pump Circuit) (2 Of 3):

Table A-5 - Engine Cranks But Will Not Run (Fuel Pump Circuit) (3 Of 3):

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. The On Board Diagnostics (OBD) System Check prompts the Technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
2. Whenever the fuse is open, a short to ground in the fuel pump feed circuit, the ignition feed circuit, or the fuel pump is the cause. Find and repair the short before replacing the fuse.
3. This step determines if the fuel pump circuit is being controlled by the PCM. The PCM should energize the fuel pump relay and turn the fuel pump "ON." If the engine is not cranking or running, the PCM should de-energize the relay and/or fuel pump within 2-3 seconds after the ignition is turned "ON."
4. Jumpering the fuel pump feed circuit to the ignition feed circuit, verifies that the fuel pump relay ignition feed circuit, the fuel pump feed circuit, the fuel pump, and the fuel pump ground are OK.
16. Replacement PCM must be reprogrammed. Refer to the latest Techline information for programming procedures.
17. This step checks the fuel pump ground circuit on the body side of the harness only.
18. Checks for an open relay ground circuit.
20. This will determine if a short to ground on the fuel pump feed circuit caused the fuse to blow. To prevent mis-diagnosis, disconnect the fuel pump harness before the test.
31. The only possible place the ignition circuit can be open is between the oil pressure switch and the fuel pump relay.