What Causes a Fuel Pump to Get a Failing Grade? -
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What Causes a Fuel Pump to Get a Failing Grade?

Adapted from Underhood Service

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We all know that just replacing an electric fuel pump won’t solve a no-fuel complaint because the pump itself is only part of the fuel delivery system. A good technician must diagnose the no-fuel problem in order to properly service the vehicle. However, here are a few of the most common reasons an electric pump fails.

  1. The simplest of reasons is a loss of current or low voltage. The pump can’t run without electricity, so anything that prevents current or voltage from reaching the pump will make it stop. This includes corroded, loose or broken wiring.

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  • Second, dirt, sediment or other debris in the tank can clog the pickup strainer, accelerate pump wear, damage the pump and/or cause the pump’s check valve to stick open (which can cause a hard starting condition due to loss of pressure when the engine is shut off). When dirt has caused a pump failure or if there appears to be a lot of dirt or sediment in the tank, the tank should be thoroughly cleaned to prevent a repeat failure.

    In fact, many pumps fail because the in-tank filter screen becomes clogged and causes the pump to overheat when the vehicle is operated with a low fuel level.

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  • The third concern is rust. Corrosion inside the tank produces rust, which can flake off and plug up the pickup strainer and have the same damaging effects on the pump as dirt. Rust is caused by condensation, which occurs during cool, humid weather when the fuel tank is low. Keeping the tank full will minimize the formation of condensation. If the tank is badly rusted or leaking, it should also be replaced.

  • Finally, normal wear. Most pumps are capable of going 100,000 miles or more, but depend on lubrication and cooling provided by the fuel itself. Frequent driving with a low fuel level may occasionally starve the pump for lubrication and cooling, which can lead to accelerated wear or even pump damage.

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    If a vehicle experiences a momentary hesitation when cornering, it may be because the fuel is sloshing away from the pump and allowing it to suck air.

    Wear also can be caused by running at excessive pressure. A faulty regulator, check valve or crimped line can cause blockages that force the pump to run at a higher-than-normal pressure – so too can a clogged fuel filter. If the underlying problem is not diagnosed and corrected, it can cause the replacement pump to fail prematurely as well.

    Signs of Failure
    Noise may sometimes be an indication of excessive pump wear. Some pumps are inherently noisier than others, often because of the way in which they’re mounted inside the tank. Noise also can be caused by a loose or missing rubber noise insulator around the pump, or physical contact with the bottom of the tank or tank baffles.

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