Refer to Engine Controls Schematics
Fuel Pump Control-Single Tank
for single tank or
Fuel Pump Controls -- Dual Tanks
for
dual tank.
Circuit Description
When the key is turned ON, the PCM energizes the fuel pump relay which sends voltage to the lift pump. The lift pump remains ON during the glow plug cycle. If the engine is not started immediately after the glow plug cycle, the PCM shuts the fuel lift pump OFF and waits for the crank reference signal.
Diagnostic Aids
Possible long crank times or a poor performance problem will exist.
Test Description
The numbers below refer to step numbers on the diagnostic table.
-
Checks for proper operation of the fuel pump.
-
Checks the operation of the fuel pump by supplying 12 volts to the fuel pump control circuit.
-
Checks the battery feed circuit to the fuel pump relay.
-
Ensures that the replacement PCM, which utilizes an electrically erasable programmable read only memory (EEPROM), is programmed when installed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the Scan Tool Capture Info in order to record the Freeze Frame and Failure records for reference, as the data will be lost when the Clear Info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Does the fuel lift pump operate during the glow plug cycle? | -- | |||
Connect a 20 amp fused jumper wire between the battery voltage circuit of the fuel pump relay and the supply voltage circuit of the fuel pump. Does the fuel pump operate? | -- | |||
Is the test lamp ON? | -- | |||
5 | Connect a test lamp between the fuel pump relay battery feed circuit harness connector and the fuel pump relay ground at the harness connector. Is the test lamp ON? | -- | ||
6 |
Is the test lamp ON during glow plug cycle and then OFF? | -- | ||
7 |
Was a problem found? | -- | ||
8 |
Is the test lamp ON? | -- | ||
9 | With a test lamp connected to B+ probe the fuel pump ground terminal, vehicle side, of the chassis harness fuel pump connector. Is the test lamp ON? | -- | ||
10 | Repair the open in the battery feed circuit to the fuel pump relay harness connector terminal. Is the action complete? | -- | -- | |
11 | Repair the open in the fuel pump relay ground circuit. Is the action complete? | -- | -- | |
12 |
Did you find and correct the condition? | -- | ||
13 | Replace the fuel pump relay. Refer to Fuel Pump Relay Replacement . Is the action complete? | -- | -- | |
14 | Replace the fuel lift pump. Refer to Fuel Lift Pump Replacement . Is the action complete? | -- | -- | |
15 | Test the supply voltage circuit of the fuel pump for an open or high resistance between the fuel pump relay and the fuel pump. Refer to Testing for Intermittent Conditions and Poor Connections or to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
16 | Repair the open in the fuel pump harness ground circuit. Is the action complete? | -- | -- | |
|
Important: The new PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
18 |
Does the engine start and continue to run? | -- | ||
19 |
Are there any additional DTCs displayed? | -- | Go to applicable DTC table | |
20 | Use the scan tool in order to select Capture Info, Review Info. Are there any additional DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
