Checking the Fuel Delivery System
CHECKING THE FUEL DELIVERY SYSTEM
For a complete wiring diagram, Refer to the Wiring Information Electrical Diagrams Electrical Diagrams.
1. CHECKING THE FUEL PRESSURE
NOTE: Diagnose and repair any fuel pump control circuit or relay DTCs before continuing with this test.
NOTE: For best results, perform Fuel Delivery System test with vehicle at room temperature. Extreme cold temperatures can cause inacurrate results.
1. Turn the ignition off.
WARNING: The fuel system is under a constant pressure even with the engine off. Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in possible serious or fatal injury.
2. Disconnect the fuel inlet hose at the Fuel Filter and attach a fuel pressure gauge with a T-fitting inline between the hose and the filter.
3. Turn the ignition on. The pump should run for 30 seconds at key on.
4. Observe the reading on the pressure gauge.
NOTE: The fuel pressure should read between approximately 50-60 psi (345-414 Kpa).
NOTE: If the pump has excessive noise or grinding, the pump should be replaced.
Select the conclusion that best matches the result of the test:
Fuel pressure is within the stated specification.
- Go To 2
Fuel pressure is below the stated specification.
- Go To 4
Fuel pressure is above the stated specification.
- Replace the Fuel Filter.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.
2. CHECKING THE FUEL PRESSURE AFTER THE FUEL FILTER
1. Turn the ignition off.
2. Remove the fuel gauge from the Fuel Filter inlet side hose and attach it between the Fuel Filter outlet port and hose.
3. Reattach the inlet hose.
4. Turn the ignition on.
5. Observe the reading on the fuel pressure gauge. Compare the reading to the pressure reading of the inlet pressure taken in step one.
NOTE: Fuel pressure should not drop more than 11.5 psi through the Fuel Filter.
Is the difference in fuel pressure measured between the inlet side and outlet side of the filter less than 11.5 psi?
Yes
- Go To 3
No
- Replace the Fuel Filter.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.
3. CHECKING THE FUEL PUMP VOLUME
1. Turn the ignition off.
2. Remove the fuel pressure gauge and attach a rubber hose to the Fuel Filter outlet port. Hold the other end of the hose into a measuring container.
3. Turn the ignition on. Record the amount of time it takes to fill 17 ounces of fuel into the container.
Did the Fuel System produce 17 ounces in less than 15 seconds?
Yes
- Test complete. Fuel Delivery System operation is normal.
No
- The most likely cause is restrictions or leaks in the fuel supply lines. If the lines are not restricted or leaking, replace the Fuel Pump.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.
4. CHECKING THE FUEL PUMP RELIEF VALVE
1. Turn the ignition off.
2. Install clamping pliers on the fuel supply hose after the fuel pressure guage. This will check maximum Fuel Pump output as well as the Pressure Relief Valve.
3. Turn the ignition on.
Is the pressure reading between 72.5 and 106 psi?
Yes
- Go To 5
No
- Check for restrictions or leaks in the fuel supply lines. If the lines are not restricted or leaking, replace the Fuel Pump.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.
5. CHECKING THE FUEL PUMP CHECK VALVE
1. Leave the clamping pliers in place on the fuel supply hose.
2. Turn the ignition off. The fuel pressure guage should hold pressure if the hose is sealed off tight with the pliers. This will check the Fuel Pump Check Valve.
Does the fuel pressure reading drop off drastically?
Yes
- If there are no leaks in the fuel supply lines, replace the Fuel Pump.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.
No
- Go To 6
6. FUEL PRESSURE SOLENOID LEAKAGE QUANTITY TEST
1. Turn the ignition off.
2. Remove the clamping pliers.
3. Remove the fuel pressure gauge and reinstall the fuel supply hose.
4. Disconnect the rubber return fuel line from the left fuel rail.
5. Attach one end of a separate rubber fuel hose to the left fuel rail. Hold the other end of the rubber hose into an appropriate container, and activate the pump by turning the ignition on.
6. Navigate the scan tool into Compression Test mode to prevent the engine from starting.
7. Crank the engine for 10 seconds and watch for leakage. There should be no noticeable leakage quantity going into the container.
Is there any leakage present?
Yes
- Replace the Fuel Pressure Solenoid.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.
No
- Go To 7
7. CHECKING THE FUEL PUMP CIRCUITS
1. Turn the ignition off.
2. Reconnect the rubber return fuel line to the left fuel rail.
3. Disconnect the Fuel Pump Module harness connector.
4. Connect a 12-volt test light between the Fuel Pump Output circuit and the Fuel Pump Ground circuit at the Fuel Pump Module harness connector (body side).
5. Turn the ignition on.
6. With a scan tool, actuate the fuel pump control to ON (100%).
NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?
Yes
- Replace the Fuel Pump.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.
No
- Go To 8
8. FUEL PUMP OUTPUT CIRCUIT CHECK
1. Using a 12-volt test light connected ground, check the Fuel Pump Output circuit at the Fuel Pump Module harness connector.
2. With a scan tool, actuate the fuel pump control to ON (100%).
NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.
Is the test light illuminated and bright?
Yes
- Go To 9
No
- Repair the Fuel Pump Output circuit. If the Fuel Pump Output circuit is o.k., replace the Body Control Module.
- Perform the BODY VERIFICATION TEST. Body Verification Test.
9. FUEL PUMP GROUND CIRCUIT OPEN OR HIGH RESISTANCE
1. Turn the ignition off.
2. Using a 12-volt test light connected to 12 volts, check the Fuel Pump Motor Ground circuit at the Fuel Pump Module harness connector.
NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.
Is the test light illuminated and bright?
Yes
- Replace the Fuel Pump Module.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.
No
- Repair the Fuel Pump Ground circuit for an open circuit or high resistance.
- Perform the ECM VERIFICATION TEST. ECM Verification Test.