Most vehicles have an electric fuel pump in the gas tank. The average life is about 100K and typical failures are hard starting or a noise from the rear of the car. Keeping your tank with a minimum of ¼ tank of gas will add life to the pump, because gas keeps the pump cool preventing premature failure.

The fuel pump’s job is twofold:

  • To push fuel from the tank to the injectors
  • To create sufficient pressure so the injectors will deliver the correct amount of fuel under all operating conditions

How to tell if your fuel pump is bad

A week fuel pump or one that can’t generate enough pressure can upset the calibration of your fuel system. This may cause the engine to run lean or starve for fuel, causing symptoms such as hard start (hot or cold), poor idle quality, hesitation or stumbling when accelerating and a loss of high speed power.

Electric fuel pumps run constantly which can cause wear on the pump causing a gradual loss of pressure and flow. Accelerated wear may also accrue if sediments or rust passed the inlet filter. A pump will fail because contaminants entered the pump and jammed it, causing the motor to overheat and burn out. If your fuel pump stops working the first thing that should be checked is the pump’s voltage supply and electrical connections.

There are mechanical fuel pumps as well. Look for gas or oil coming from the pump. Check out any “gassy” smells. If your oil level starts to rise above the full mark, the extra volume in your oil is probably gasoline. Cars can’t make oil, they only lose it. The best way to test a mechanical fuel pump is with a fuel pressure gauge. Normal pressure is at least 4 pounds. If the tests determined a bad fuel pump, pumps fail in the following ways: diaphragm leak, valve failure, and cam to pump mechanical failure. Fuel line leaks are something else to check out. If a fuel line gets a leak on the suction side the pump can suck air and stop pumping fuel. That’s one good thing about checking the pump with a fuel pressure gauge, it will show a pressure being made even if fuel is not being pumped. If you have a fuel pump that makes pressure on one side and creates a vacuum on the other, then it’s a good pump. There may be a fuel line, filter, or tank problem.

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