Chart 3 of 3 - Fuel Delivery

Diagnostic Chart 3:

Schematic:

The ECM controls the fuel pump motor by supplying 12 volts to the fuel pump relay coil circuit. The fuel pump runs continuously whenever the engine is running or cranking. The fuel pump is fed battery voltage whenever the fuel pump relay is turned On. The main relay must be turned On in order for current to flow to the relay coil circuit.

DIAGNOSTIC AIDS

IMPORTANT:
^ If DTC P0628 or P0629 is set, diagnose that DTC first.
^ The ECM will NOT command the fuel pump relay On unless the engine is cranking or running.

Fuel rail pressure: 345-414 kPa (50-60 psi)

Fuel pump relay coil resistance: 70-115 ohms