Fuel pump/fuel pressure — check Ford F150
Warning: Gasoline is extremely flammable, so take extra precautions when you work on any part of the fuel system. See the Warning in Fuel pressure relief procedure.
Note: After the fuel pressure has been relieved, it’s a good idea to lay a shop towel over any fuel connection to be disassembled, to absorb the residual fuel that may leak out when servicing the fuel system.
General checks
Note: The fuel pump relay is equipped with a primary and secondary voltage circuit. The primary circuit is controlled by the PCM and the secondary circuit is linked directly to battery voltage from the ignition switch. With the ignition switch On (engine not running), the PCM will ground the relay for one second. During cranking, the PCM grounds the fuel pump relay as long as the reference signal from the ignition system is received. If there are no reference pulses, the fuel pump will shut off after two or three seconds.
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.
- Check the fuel filter for restriction.
- Inspect all fuel lines to ensure that the problem is not simply a leak in a line.
2. Verify the fuel pump actually runs. Place the transmission in Park (automatic) or Neutral (manual) and apply the parking brake. Have an assistant turn the ignition switch to On — you should hear a brief whirring noise as the pump comes on and pressurizes the system. 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.
Note: The fuel pump is easily heard through the gas tank filler neck.
3. If the pump does not turn on (makes no sound) with the ignition switch in the On position, check the ignition fuse located in the engine compartment fuse center. Also, check the fuel pump relay. Refer to Chapter 12 for testing relays.
Note: The fuel pump relay is located in the fuse/relay center in the engine compartment (see Troubleshooting).
4. If the relays are good and the fuel pump does not operate, check the fuel pump circuit. If the wiring and the connectors are good, either the FPCM (see Fuel Pump Driver Module (FPDM) – replacement) or the fuel pump (see Fuel pump/fuel pump module — removal and installation) is faulty.
Note: The PCM commands the fuel pump control module (FPCM), which in turn operates the fuel pump at either 8 or 12 volts. If you suspect that the fuel pump control module is faulty, have the system diagnosed at a dealer or a qualified repair shop. Refer to Chapter 6 for information on replacement of this component.
Fuel pump pressure check
Warning: Never attempt to measure the fuel pressure on the high-pressure side of a Direct Injection system.
Note: The following procedure applies to the complete Sequential Fuel Injection (SFI) system (also know as multi-port fuel injection) and the fuel system before the high-pressure pump on Direct Injection (Dl) systems. Dl systems operate under very high pressures and require special tools to diagnose correctly. Note: Before proceeding, obtain a fuel pressure gauge capable of measuring fuel pressure well above the specified operating range of the fuel system you’re going to test, and you’ll also need fittings suitable for tee-ing the gauge into the fuel system between the fuel delivery line and the fuel rail.
5. Relieve the fuel system pressure (see Fuel pressure relief procedure).
This fuel pressure testing kit contains all the necessary fittings and adapters, along with the fuel pressure gauge, to test most automotive systems
6. In addition to a fuel pressure gauge capable of reading fuel pressure up to 100 psi, you’ll need a hose and an adapter suitable for tee-ing into the fuel system at the quick-connect fitting between the fuel delivery hose and the fuel rail
7. On SFI systems, disconnect the quick-connect fitting at the connection between the fuel delivery hose and the fuel rail (if you’re unfamiliar with quick-connect fittings, refer to Fuel lines and fittings – general information and disconnection). Tee in the fuel pressure gauge between the fuel delivery hose and the fuel rail.
Location of the fuel line quick-connect fitting on the high-pressure fuel pump at the rear of the right-side cylinder head (2.7L model shown)
8. On DI systems, disconnect the quick-connect fitting at the connection between the fuel delivery hose and the high-pressure fuel pump. Tee in the fuel pressure gauge between the fuel delivery hose and the high-pressure fuel pump
9. Turn the Key On, Engine Off (KOEO) and check for fuel leaks from the fuel pressure test adapter fittings.
10. Turn off all the accessories, then start the engine and let it idle. The fuel pressure should be within the operating range listed in this Chapter’s Specifications. If the pressure reading is within the specified range, the system is operating correctly.
11. If the fuel pressure is higher than specified, then the pump, the Fuel Pump Driver Module (FPDM), the Powertrain Control Module (PCM) or the circuit connecting these components is probably defective. But checking this circuit is beyond the scope of the home mechanic, so have the circuit checked by a professional.
12. If the fuel pressure is lower than specified, inspect the fuel delivery lines and hoses for an obstruction or a kink. Also inspect all fuel delivery line and hose quick-connect fittings for leaks. If the lines, hoses, and connections are all in good shape, remove the fuel pump/fuel level sensor assembly (see Fuel pump/fuel pump module – removal and installation) and inspect the fuel pump inlet strainer for restrictions. If everything else is okay, replace the fuel pump.
13. Turn the ignition switch to Off, wait five minutes and recheck the pressure on the gauge. Compare the reading with the hold pressure listed in this Chapter’s Specifications. If the hold pressure is less than specified:
- The fuel delivery line or a quick-connect fitting might be leaking.
- A fuel injector (or injectors) may be leaking.
- The fuel pump might be defective.
14. After the testing is complete, relieve the fuel pressure (see Fuel pressure relief procedure), remove the fuel pressure gauge and reconnect the fuel delivery line to the fuel rail.