Component Tests and General Diagnostics

Diagnostic Chart 1 Of 3:

Diagnostic Chart 2 Of 3:

Diagnostic Chart 3 Of 3:

Fuel System Diagnosis:

SYSTEM DESCRIPTION
The fuel supply system is a returnless design that has most of the fuel system components located inside of the fuel tank. When the ignition switch is turned to the START position and the engine is cranking, the circuit opening relay will be energized in order to allow the fuel pump to operate and pressurize the system. The fuel pump will continue to operate if the Powertrain Control Module (PCM) receives a reference signal when the engine is started. The fuel pump operates as long as the circuit opening relay is energized by the PCM. When the circuit opening relay is de-energized, the fuel pump will stop operating. The fuel pump delivers fuel to the fuel rail at high pressure. The fuel pressure regulator, located in the fuel tank, is responsible for keeping the fuel pressure at 301-347 kPa (44-50 psi).

DIAGNOSTIC AIDS
Verify that the fuel pressure regulator has not become loose or mispositioned. This may cause a low fuel pressure condition.

Check for leakage around all fuel hose and fuel pipe connections. A plugged fuel injector could be the cause of a hard or no-start condition or loss of power. An erratic fuel pressure may be caused by a fault in the fuel pump electrical circuit. Inspect the wiring harness and components for any of the following conditions:
^ Any backed-out terminals
^ Any improper mating of terminals
^ Any broken electrical connectors locks
^ Any improperly formed or damaged terminals
^ Any faulty terminal-to-wire connections
^ Any physical damage to the wiring harness
^ A broken wire inside the insulation
^ Any corrosion of the electrical connections, the splices, or the terminals

TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.
1. The 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.
6. This step checks the fuel pump for a worn bearing or a binding impeller. The pump should have a smooth and steady low humming sound. A loud humming or growling noise may indicate a faulty fuel pump. Check a known good vehicle in order to compare pump operation.
12. The fuel system can not maintain constant fuel pressure with a leak in any of the following areas:
^ The fuel pump check valve
^ The valve or valve seat within the fuel pressure regulator
^ The fuel injectors
17. This step checks whether the fuel system is leaking between the fuel pressure gauge and the fuel injectors or between the fuel pressure gauge and the fuel sender assembly.
20. This step checks for additional conditions that can cause low fuel pressure other than a faulty fuel pump. Check for any restrictions or blockage in the fuel feed lines and hoses, including those inside the fuel tank. Check the fuel pump electrical circuit for excessive resistance. Proper fuel pump operation requires correct voltage and adequate current flow.
23. Check for rust and other foreign materials in the fuel tank. Clean or replace the fuel tank as necessary.