Fuel Delivery and Air Induction: Testing and Inspection

FUEL SYSTEM DIAGNOSIS

SYSTEM DESCRIPTION
The fuel supply system is a returnless design. Most of the fuel system components are located inside the fuel tank. When the ignition switch is turned to the START position and the engine is cranking, the circuit opening relay energizes the fuel pump. 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).

TEST DESCRIPTION

Step 1 - Step 9:

Step 10 - Step 19:

Step 20 - Step 25:

The numbers below refer to the step numbers on the diagnostic table.
1. The Diagnostic System Check-Vehicle 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:
- Fuel pump check valve
- Valve or valve seat within the fuel pressure regulator
- Fuel injectors
17. This step checks whether the fuel system is leaking between the fuel pressure gage and the fuel injectors or between the fuel pressure gage 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.