Fuel Pressure: Testing and Inspection

WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF). BEFORE PERFORMING THE FUEL PUMP PRESSURE TEST, THE FUEL SYSTEM PRESSURE MUST BE RELEASED.

PROCEDURE

1. Fuel system pressure must be released each time a fuel hose is to be disconnected. Perform the preceding Fuel System Pressure Release procedure before checking fuel system pressure.

2. Disconnect 5/16 fuel supply hose from the engine fuel line assembly. Use care when removing the fuel hose to prevent damage to the hose or the fuel line. Replace hose if damaged. Connect fuel system pressure tester (C-4799B) between fuel supply hose and engine fuel line assembly.

3. Obtain DRB II diagnostic tester. Place the ignition key in the Run position. Using the DRB II Actuator Test, access the ASD Fuel System Test. This will activate the fuel pump and pressurize the system.

4. If the gauge reads 100 kPa ±7 kPa (14.5 psi ± 1 psi), pressure is correct. Further testing is not required. Install fuel hose using a new original equipment type clamp. Tighten to 1 Nm (10 in. lbs.) torque. If pressure is not correct, record the pressure and proceed to step number 5.

5. If fuel pressure is below specifications, install pressure tester in the fuel supply line. This will be between the fuel tank and fuel filter at the rear of vehicle.

6. Repeat test. If pressure is 5 psi higher than previously recorded pressure, replace fuel filter. If change is not observed, gently squeeze return hose. If pressure increases, replace pressure regulator. If change is not observed, problem is either a plugged pump filter (sock) or defective fuel pump.

7. If pressure is above specifications, remove the fuel return line hose from the chassis line at fuel tank. Connect a 3 foot piece of fuel hose to the return line. Put the other end into an approved gasoline container (minimum 2 gallon size). This is used to collect excess fuel. Repeat test. If pressure is now correct, check in-tank return hose for kinking. Replace fuel pump assembly if in-tank reservoir check valve or aspirator jet is obstructed. This test should be performed when fuel tank is 1/2 full or greater.

8. If pressure is still above specifications, remove fuel return hose from throttle body. Connect a substitute hose to the throttle body return nipple and place other end of hose in clean container. Repeat test. If pressure is now correct, check for restricted fuel return line. If change in pressure is not observed, replace fuel pressure regulator.