Fuel System Diagnosis

Fuel Pressure Test:

1. Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to the test port (schrader valve) on the fuel rail. Make sure lines and hoses are clear, START the engine, and observe the fuel pressure. The fuel pressure should rise to approximately 214 kPa (31 psi), and remain there.
a. If the fuel pressure reading is below the specification, STOP the engine and proceed to step 2.
b. If the fuel pressure is above specification, STOP the engine and proceed to step 5.
c. If the fuel pressure reading is correct, no further fuel pump testing is necessary, however fuel pressure may be bleeding off while the engine is stopped. Service and Repair
2. START the engine, remove the vacuum hose to the fuel pressure regulator, and note the fuel pressure. The pressure should rise approximately 55-69 kPa (8-10 psi). If there is no increase in fuel pressure, momentarily pinch off the fuel return line. If the fuel pressure increases, replace the fuel pressure regulator, and retest the operation. If fuel pressure does not increase proceed to step 4.
3. START the engine and allow it to run at idle. Momentarily pinch the fuel return line and observe the fuel pressure. If the pressure fails to increase, the problem is a blockage at the fuel filter, or a defective fuel pump. If the fuel pressure rises, STOP the engine, replace the fuel pressure regulator, and retest the operation.
4. Install another fuel pressure gauge in the fuel line between the tank and the fuel filter. START the engine, and note the fuel pressure on both gauges. If the pressure difference on the in-line gauge is 34.5 kPa (5 psi) or more than the pressure at the fuel rail, the fuel filter needs to be replaced. If there is no difference in pressure, the fuel pump is defective and must be replaced. STOP the engine, replace the necessary component and retest the operation.
5. Disconnect the fuel return line at the fuel pressure regulator. Connect a sufficient length of hose to the return line, and direct the hose into a suitable container, marked "gasoline". START the engine and observe the fuel pressure. If the fuel pressure reads normal, the problem is a blockage in the fuel return line. If the pressure still reads above normal, the fuel pressure regulator is defective and must be replaced. STOP the engine, replace the necessary component and retest the operation.