Fuel pressure – check
Warning: Gasoline is extremely flammable. See Fuel system warnings in Section Fuel and exhaust systems.
Note: The following procedure assumes that the fuel pump is receiving voltage and runs.
General checks
1. If you suspect insufficient fuel delivery check the following items first:
- Check the battery and make sure it’s fully charged (see Engine electrical systems).
- Check the fuel pump fuse.
- Inspect all fuel lines to ensure that the problem is not simply a leak in a line.
2. Verify the fuel pump actually runs. Have an assistant turn the ignition switch to On — you should hear a brief whirring noise (for approximately two seconds) as the pump comes on and pressurizes the system.
Note: The fuel pump is easily heard through the fuel tank filler neck. If there is no response from the fuel pump (makes no sound), check the fuel pump electrical circuit. If the fuel pump runs, but a fuel system problem is suspected, continue with the fuel pump pressure check.
Fuel pump pressure check
Note: In order to perform the fuel pressure test, you will need to obtain a fuel pressure gauge capable of measuring high fuel pressure and the proper adapter set for the specific fuel injection system.
Note: The fuel filter is mounted in the fuel pump assembly.
3. Relieve the fuel system pressure (see Troubleshooting).
4. Disconnect the fuel tube connector at the fuel rail and connect the fuel pressure gauge using the proper adapters (see illustrations).
i. 4a This fuel pressure testing kit contains all the necessary fittings and adapters, along with the fuel pressure gauge, to test most automotive systems
i. 4b Fuel feed line fitting at the fuel rail
5. Turn all the accessories Off and switch the ignition key On. The fuel pump should run for about two seconds; note the reading on the gauge. If the fuel pressure is higher thanspecified, replace the fuel pressure regulator. If the pressure is too low, the fuel filter (or in-tank strainer) could be clogged, the lines could be restricted or leaking, a fuel injector could be leaking, or the fuel pressure regulator and/or the fuel pump could be defective.
6. Start the engine and let it idle at normal operating temperature. The pressure should fall within the range listed in this Chapter’s Specifications. If the pressure is lower than specified, check the items listed above.
Note: If no obvious problems are found, most likely the fuel pressure regulator and/or the fuel pump is defective. In this situation, it is recommended that both the fuel pressure regulator and fuel pump are replaced to prevent any future fuel pressure problems.
7. Turn the engine off and check the gauge -the pressure should hold steady. After five minutes it should not drop below the minimum listed in this Chapter’s Specifications. If it does drop, the fuel pump or pressure regulator could be defective, or a fuel injector could be leaking.
8. After the testing is done, relieve the fuel pressure (see Troubleshooting) and remove the fuel pressure gauge.