The following tests will include: pressures tests of fuel transfer pump (engine running and engine cranking), a test for supply side restrictions, and a test for air in fuel supply side.
Refer to Fuel Transfer Pump Description/Operation for an operational description of transfer pump.
The fuel transfer (lift) pump is located on left side of engine and above starter motor (Fuel Transfer Pump Location).
An improperly operating fuel transfer pump, a plugged or dirty fuel filter, or a defective overflow valve can cause low engine power, excessive white smoke and/or hard engine starting.
Before performing following tests, inspect fuel supply and return lines for restrictions, kinks or leaks.
Fuel leaking from pump casing indicates a leaking pump which must be replaced.
Pressure Test: Because the transfer pump is operating at two different pressure cycles (engine running and engine cranking), two different pressure tests will be performed.
Fuel Supply Restriction Test:
Due to very small vacuum specifications, the DRB scan tool along with the Periphal Expansion Port (PEP) Module and 0-15 psi transducer must be used.
WARNING: DO NOT STAND IN LINE WITH THE COOLING FAN FOR THE FOLLOWING STEPS.
Testing For Air Leaks in Fuel Supply Side:
To prevent engine from starting in this test, first remove fuel system relay (fuel injection pump relay). Relay is located in Power Distribution Center (PDC). Refer to label under PDC cover for relay location.
Because fuel pump relay was removed, a Diagnostic Trouble Code (DTC) may have been set. After testing is completed, and relay has been installed, use DRB scan tool to remove DTC.