Circuit Diagnosis - Fuel Pump Relay

Engine Cranks But Does Not Run (Fuel Pump Circuit [1 Of 4]):

Engine Cranks But Does Not Run (Fuel Pump Circuit [2 Of 4]):

Engine Cranks But Does Not Run (Fuel Pump Circuit [3 Of 4]):

Engine Cranks But Does Not Run (Fuel Pump Circuit [4 Of 4]):

Engine Controls (Fuel Pump Relay & Fuel Level Sensor):

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 remains on as long as the PCM receives the ignition reference pulses from the Ignition Control Module (ICM). If there are no references pulses, the PCM will shut off the fuel pump about 2 to 3 seconds after the key on, or about 10 seconds after the reference pulses stop. Whenever sufficient oil pressure is present to close the oil pressure switch, the fuel pump will remain on during the cranking without the 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. The excess fuel is then returned to the fuel tank.

Improper fuel system pressure may result in one or more of the following symptoms:

^ Cranks but will not run
^ DTC P0171
^ DTC P0172
^ DTC P1171
^ DTC P0300
^ Outs out, may feel like an ignition problem
^ Poor fuel economy
^ Loss of power
^ Hesitation

Diagnostic Aids
A failed pump relay results in an extended engine crank time because of the time required to build enough oil pressure in order 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 in order to build enough oil pressure in order to close the switch. This or a faulty oil pressure switch can result in an Engine Cranks But Will Not Run condition.

Test Description
The numbers below refer to the step numbers in the diagnostic table.

1. The Powertrain 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 occurs. 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 terminal, 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 or the fuel pump within 2 to 3 seconds after the ignition is turned ON.
4. Jumpering the fuel pump feed terminal 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. Reprogram the replacement PCM. Refer to the latest Tech line information for programming procedures.
17. This step checks the fuel pump ground circuit on the body side of the harness only.
18. This step checks for an open re)ay ground circuit.
20. This step will determine if a short to ground on the fuel pump feed terminal caused the fuse to open. In order to prevent mis-diagnosis, disconnect the fuel pump harness before the test.
31. The only possible place the fuel pump relay ignition feed terminal can be open is between the oil pressure switch and the fuel pump relay.