Chart 4 of 4 - Fuel Delivery

Diagnostic Chart Part 4:

Schematic 4:

The ECM controls the fuel pump motor by supplying the fuel pump relay coil ignition voltage. The fuel pump runs continuously whenever the engine is running or runs for 2 seconds if the ignition is turned On and the engine is not cranked. The ECM controls an internal driver, which supplies the fuel pump relay coil direct ignition voltage whenever the fuel pump is commanded On. The fuel pump is fed battery voltage whenever the fuel pump relay is turned On.

DIAGNOSTIC AIDS
The fuel pump will run for 2 seconds when the ignition is first turned On and no CKP signal is received at the ECM.

The Scan tool can be used to command the FUEL PUMP On and Off instead of cycling the ignition key.

The ignition must be Off for 10 seconds before the ECM will turn On the fuel pump relay when no CKP signal is received at the ECM.

To perform an accurate fuel pressure reading, the fuel pump should be cycled three times.

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

Fuel pump relay coil resistance: 70-115 ohms