Checking to see if your fuel pump is priming is crucial to making sure that the fuel system on your car is working to capacity. If the unit will not prime, it means that it fails to build up its pressure by pumping fuel from the tank to the engine (and returning whatever it does not use before ignition—an integral part of its design) within approximately three seconds when you turn on your vehicle and have some ignition.
Hear the Priming Sound: The quickest way to find out whether or not your fuel pump is priming is to listen for a faint humming sound when you put your key in the ignition and turn it to accessory but without turning the engine over. This humming noise takes a couple of seconds, which means the fuel pump is giving pressure to the system. · If there is no sound, then the pump may either not be getting power or it has died.
Inspect Fuel Pressure: It is likely that fuel pressure should be somewhere between 30 to 60 psi for most vehicles that use fuel injection. If you have access to a fuel pressure gauge, connect it at the fuel rail and double check that your pump is building appropriate pressure during prime mode. Low or no pressure means a priming issue, which could come from the pump itself or any related parts, like the fuel filter or relay.
Check Engine Performance: If your fuel pump is primed But fails to check, you can still try to crank the engine but it will not start. For example, inadequate priming can cause sporadic starts, stalling or a poor idle. If your engine requires a period of cranking after sitting for several hours it's possible the pump isn't pressurizing the fuel system adequately.
Check Fuel Pump Relay and Fuse: The fuel pump relay or fuse may not be allowing the fuel pump to prime if they are broken. This relay should turn the fuel pump "ON" with 12 volts. A multimeter is the only way to know the relay and fuse are good. Change the blown fuses or just replace the relays that are not functioning to have priming.
A 2019 automotive study showed that 20% of electric fuel pump failures were priming-related, emphasizing this first process within the Fuel Pump delivery sequence.
Check Power to Fuel Pump: If you're not sure the pump is priming, go back to when you checked for power at the fuel pump connector. This pump runs on 12 volts, and at below that or if voltages fluctuate the priming will fail. Using a multimeter to check will make sure the pump is getting power with ignition.
A wise man once said, Henry Ford that is, "Quality means doing it right when no one is looking. One of the things you must always verify is the priming function of your fuel pump if you want to keep up high performance vehicle.
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