What is a fuel pump?
Your fuel pump moves gasoline from the tank forward to the engine compartment. At the same time it provides the pressure to spray fuel into the engine through the fuel injectors. Powered by electricity, the pump is generally mounted inside the fuel tank. It takes fuel in, pressurizes it and feeds it into a fuel line that takes it up to the engine compartment. There, a pressure regulator returns excess fuel not needed by the engine back to the tank through a parallel line. Fuel pumps used today generally produce 30-60 lbs. of pressure, roughly as much pressure as the water in your household plumbing. The inlet to the pump is filtered by a plastic “sock” to keep debris out of the pump and your engine. The fuel-level sender is usually mounted directly to the pump. Diesels or higher-tech Direct-Injection gasoline engines have a second, high-pressure injection pump mounted to the engine.
What are the symptoms of a faulty fuel pump?
Often, a pump will become noisy as it nears failure, making a whining noise audible in the car. Sometimes a noisy pump will survive for years, so that’s not necessarily a good indication. You should be able to hear the pump run for a few seconds after you turn on the key. Have someone turn the key from OFF to ON (without going further into the START position) while you lean down near the rear of the vehicle. The pump noise will continue for 4-5 seconds before it shuts off. This shutdown is programmed into the car’s computer to prevent the fuel pump from running down the battery if the engine stalls. More importantly, it prevents the pump from pumping fuel in the event of an accident that may have ruptured a fuel line, feeding a fire after an accident.
A non-running fuel pump may have a wiring issue, or it may have simply failed. A mechanic will need to check the wiring, or check the fuel pressure with a gauge underhood to determine the problem. A clogged in-tank fuel sock or a plugged-up under-hood fuel filter can mimic a failing pump, making the car run poorly or intermittently. Your mechanic will have to make the final diagnosis.
What is the severity of a failed fuel pump?
Obviously, a non-running fuel pump will keep your car from starting or running. A failing pump may make your car run poorly or intermittently. When your mechanic diagnoses a bad pump, it will need to be replaced. Because the pump is generally located inside the fuel tank, this usually means removing the fuel tank from underneath the vehicle to access it. This also requires emptying the tank before removing it.
The pump itself will cost $75-200. Labor costs are highly dependent on the exact vehicle. If the pump is accessible without removing the tank (a few vehicles allow access to the pump from under the backseat,) expect to pay less than $100 for labor. If the tank must be removed, sometimes much of the exhaust system must be removed as well, and the labor could easily reach $300. A diesel or Direct-Injection pump could cost well over a thousand dollars to replace.
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