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Common Causes of Electric In-tank Fuel Pump Failures

Posted on 4/6/2016 11:04:13 AM

Fuel tank contamination is the number one cause of in-tank electric fuel pump failures. This contamination is often the result of moisture in the fuel tank leading to fuel tank oxidation,
causing rust to form in the fuel tank. The rust is then ingested by the fuel pump, ultimately bringing about pump failure. 

A widespread misconception is that the fuel pump strainer or sock on the inlet side of the fuel pump will prevent these contaminates from entering the pump. WRONG! Fuel pump strainers will not stop moisture or particles of contamination smaller than 70 microns (on average). Why not simply use a finer filter strainer and eliminate these problems? If a strainer was made fine enough to keep out all of the contaminates and still allow proper fuel flow volume, it would be too large to fit in the fuel tank. The strainers used today are a middle-of-the-road balance between allowing adequate fuel flow and maximum fuel filtering. Original Equipment and Aftermarket replacement pumps are built to supply high pressure fuel to injection systems and are engineered with the assumption of a clean, cool, fuel supply to the pump at all times.Injection systems are even more sensitive to contaminants; that’s why the industry standard is in-line fuel filters that capture, on average, particles approximately 30 microns or larger. Further downstream in the fuel system, fuel injector filters capture particles as small as 10 microns.So it becomes obvious that any contamination in the fuel tank can cause premature fuel pump failure.If you find you are replacing a fuel pump that has a discolored strainer, properly dispose of the fuel you drained; it is contaminated too. If you put the same fuel back into the tank after the pump is replaced, you are reintroducing contaminants immediately! Always replace the fuel pump strainer and fuel filter with new units when replacing a fuel pump. 

Electrical connections are the second most common causes of fuel pump replacement. In reality,the fuel pump is still quite capable of providing pressure and flow well within specifications,but because of poor electrical connections the output is diminished, giving the appearance of a failed pump.To identify fuel pump electrical problems, use a high quality digital volt/ohm/meter to test for voltage drops and continuity. This test must be done with the pump running.NOTE: In a 12-volt system, fuel pumps are designed to run at 13.5 volts. Maximum voltage drop of more than .2 volts will affect the fuel pump operation. 

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