For 1990-2009 cars

### System Description

The fuel pump fuse provides system voltage to the fuel pump relay. The PCM grounds the Fuel Pump Relay control circuit to energize the fuel pump relay. When the ignition is turned ON, the PCM commands the fuel pump relay ON for at least 2 seconds, voltage is applied to the electric fuel pump and will continue to energizes the fuel pump after the PCM receives 3X reference pulses. The fuel pump is an electric pump and is part of the Modular Fuel Sender Assembly. The fuel pump supplies fuel through an in-line fuel filter, fuel rail assembly to the fuel injectors. A fuel pressure regulator, attached to the fuel rail assembly, maintains a regulated fuel pressure for correct operation of the fuel injectors. Any unused fuel is then returned to the fuel tank by a separate fuel return pipe.

### Fuel System Diagnosis

Checks | Action
--- | ---
Under suspected fuel failure conditions refer to the following fuel systems symptoms:
Starting Point | Perform the Powertrain On-Board (OBD) Diagnostic System Check. Refer to Powertrain On Board Diagnostic (OBD) System Check .
Fuel Control Circuit | Perform the following tests:

• | Engine Cranks but Does Not Run

• | Fuel Pump Electrical Circuit Diagnosis

• | DTC P0230 Fuel Pump Relay Control Circuit

This will determine if the problem is caused by the ignition system, the PCM, or the fuel pump electrical circuit.

Fuel Delivery/Performance | The Fuel System Pressure Test will determine if adequate fuel pressure is available. Refer to Fuel System Pressure Test .
Fuel Related Misfire | Perform the following tests if fuel related misfire is indicated:

• | Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F)

• | Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Outside 10-35 Degrees C (50-95 Degrees F)

• | Fuel Injector Balance Test

• | DTC P0201-P0206 Fuel Injection Control Circuit

These tests will determine if the temperature related coil windings or mechanical ability of the fuel injectors malfunctions.

Fuel Metering System | If changes in fuel calculation are indicated on a scan tool refer to the following Diagnostics:

• | The DTC P0171 Fuel Trim System Lean .

• | The DTC P0172 Fuel Trim System Rich .

Fuel Contamination | Fuel Contamination can cause driveabilty problems such as hesitation, lack of power, stall or no start. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
Fuel Economy | Poor fuel economy can be caused by conditions not related to the fuel system. Refer to Poor Fuel Economy .
Fuel Fill Quality | Poor Fuel fill Quality can be caused by an ORVR system malfunction or improper owner operation during fueling. Refer to Poor Fuel Fill Quality .