Fuel Pump: Testing and Inspection

Diagnostic Chart 1 Of 2:

Diagnostic Chart 2 Of 2:

Schematic:

SYSTEM DESCRIPTION
The Powertrain Control Module (PCM) will energize the fuel pump relay for 2 seconds when the ignition switch is turned to the ON position. The fuel pump pressurizes the fuel system when the fuel pump relay is energized. The PCM receives ignition system reference pulses if the engine is being cranked or if the engine is running. The PCM will continue to energize the fuel pump relay as long as the PCM receives ignition system reference pulses. The PCM will de-energize the fuel pump relay if the ignition system reference pulses are no longer detected.

The fuel pump will deliver fuel to the fuel injector in the TBI unit at a controlled pressure. The controlled pressure is 160-210 kPa (23-31 psi) when the fuel pump is energized and the engine is not running. The controlled pressure is 90-140 kPa (13-20 psi). When the engine is idling at normal operating temperatures The fuel-pressure regulator maintains the correct fuel pressure at all times by returning excess fuel to the fuel tank.

DIAGNOSTIC AIDS
Incorrect fuel system pressure can result in any of the following conditions:
^ The engine cranks but will not start.
^ The engine cuts out or stalls. This may feel like an ignition malfunction.
^ A decrease in fuel economy and a loss of power.
^ Hard starting

Check for water contamination of the fuel if the vehicle will not start in freezing weather. Ice can form in the fuel system and prevent the fuel from reaching the fuel injectors at the required pressure and volume.

The normal fuel pump electrical resistance is 0.8-1.5 ohms at 20°C (68°F).

An intermittent malfunction may be caused by a problem in the fuel pump electrical circuit. Inspect the wiring harness and the components for any of the following conditions:
^ Backed out terminals
^ Incorrect mating of terminals
^ Broken electrical connector locks
^ Incorrectly formed terminals or damaged terminals
^ Faulty terminal-to-wire connections
^ Physical damage to the wiring harness
^ A broken wire inside the insulation
^ Corrosion of electrical connections, of splices, or of terminals

TEST DESCRIPTION
The numbers below refer to the step numbers in the Diagnostic Table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
3. This step checks to see if fuel system pressure is within specifications with the ignition ON, and the fuel pump running.
4. This step checks the fuel pressure after the fuel pump stops. Approximately one minute after the fuel pump stops fuel pressure should remain steady at 90 kPa (13 psi).
6. This step checks for a faulty check valve in the fuel pump.
7. This step checks for a faulty fuel pressure regulator.
10. This step checks for a faulty fuel pressure regulator.
14. This step checks the operation of the fuel pressure regulator.