Circuit/System Testing
- Verify the following conditions do not exist:
- Hoses and lines that are flattening when the engine is running, or have kinks that would restrict the flow of fuel
- Fuel leaks between the fuel tank and the fuel injection pump
- Fuel leaks in the fuel return lines
IMPORTANT: A fuel return line that is leaking, is a good indication there is a restriction in the return system.- Repair any leaks, restrictions, or replace any components found to be damaged or leaking.
- Install the fuel pressure gage. Refer to Fuel Pressure Gage Installation and Removal .
- Prime the fuel system. Refer to Fuel System Priming .
- Ignition ON, command the fuel pump relay ON with a scan tool. Verify the fuel pressure is between 415-535 kPa (60-78 psi)
and remains steady for 5 minutes.
- If less than the specified range, remove the fuel tank and test, inspect, and repair the items listed below. If all items test normal, replace the fuel pump.
- Leaking fuel lines
- Restricted fuel feed pipe
- Restricted or plugged strainer
- Stuck or binding fuel level float
- Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
- If less than the specified range, remove the fuel tank and test, inspect, and repair the items listed below. If all items test normal, replace the fuel pump.
- If the fuel system components test normal, test or replace the fuel filter.
IMPORTANT:
It may be necessary to remove engine components for the visual inspections.
IMPORTANT:
The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.