Fuel Pressure: Testing and Inspection

WARNING: The 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.

1. Perform the Fuel Pressure Release procedure before checking fuel system pressure.
2. Disconnect the 5/16 inch 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. Activate the fuel pump and pressurize the system using the DRB scan tool (or equivalent).
4. If the gauge reads 100 Kpa +/- 7 Kpa (14.5 PSI +\- 1 PSI), pressure is correct and further testing is not required. Reinstall 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 the fuel filter at the rear of the vehicle.
6. Repeat test. If the pressure is 5 PSI higher than the previously recorded pressure, replace fuel filter. If a change is not observed, gently squeeze return hose. If pressure increases, replace the pressure regulator. If a change is not observed, the problem is either a plugged fuel pump filter (at the fuel pump module) or defective fuel pump.
7. If fuel pressure is above specifications, remove the fuel return hose from the chassis line at the 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 return line 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 the throttle body. Connect a substitute hose to the throttle body return nipple and place the other end of hose in a clean container. Repeat test. If pressure is now correct, check for restricted fuel return line. If change in pressure is not observed, replace the fuel pressure regulator.