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What Causes Fuel Pump Failure and How to Prevent It

Learn The Most Common Causes of Fuel Pump Failure

If your fuel pump just bit the dust, you’re probably wondering what causes fuel pump failure. The fuel pump on a fuel-injected vehicle is located inside the gas tank. It’s there for a reason. An electric motor powers these pumps, and engineers place the pump in the tank so the gasoline can cool the electric motor. You would think placing the pump in the tank is a bad design because you’d have to drop the tank to change a fuel pump. That’s not how the engineers see it. That’s because they designed the pump to last the life of the vehicle.

1) Fuel contamination Is a Major Cause Of Fuel Pump Failure

Tank corrosion, debris in the tank, and moisture, are the most common cause of fuel pump failure. Yes, the fuel pump module contains a filter sock, but if you

causes fuel pump failure

Rusty tank and fuel pump

have an old rusty tank with dirt and rust particles; they can get sucked into the pump and wear out the impeller.

Not cleaning the tank after a fuel pump failure is the #1 cause or repeat fuel pump failures.

2) Clogged strainers or filters

Tank contaminants eventually clog critical components, including strainers and the fuel filter. Those clogs force the pump to constantly work harder to deliver the same pressure and column, causing it to fail early. Because the blockage impairs the flow of fuel, your engine may exhibit less power and a lack of acceleration.

3) Electrical issues can cause a fuel pump to go bad

While the fuel pump sits inside the tank, the electrical connection is above the tank, exposing it to water, salt, and all kinds of critters and insects. Any time an electrical motor experiences a drop in voltage, either on the power side or on the ground side of the circuit, the motor draws more amps, which means more heat. That extra heat degrades the motor windings, caused early failure.

That’s why you should check the fuel pump ground connection first if you suspect a fuel pump issue. Use a multimeter to check for voltage drop on the ground side of the circuit. Then, check for corrosion in the connectors, loose terminals, or signs of melting in the connector.

4) Running low on fuel can speed up fuel pump failure

Carmakers move the fuel pump to the tank for a reason; to keep it cool. The electric motor fuel pump relies on the fuel in the tank to cool it. Repeatedly running your vehicle when it’s low on fuel deprives the fuel pump of the cooling it needs to prevent premature wear. If you constantly drive around with less than ¼ tank, don’t be surprised that your fuel pump fails early.

What wears out on a fuel pump?

The early fuel-injected fuel pumps used brushed DC motors. Brushed motors generate approximately 100°F heat near the armature, so the engineers rely on the colder fuel in the tank to dissipate this heat.

When the vehicle is run with low fuel, the brushes overheat and deposit carbon particles on the copper armature contacts. This carbon buildup increases electrical resistance, which reduces the motor’s power. Once the resistance gets high enough, the pump can’t build enough fuel pressure to supply the fuel injectors.

The carbon deposits also create heat in the electrical connectors, sometimes causing the plastic components to melt.

Dirt and debris also clog the check valve

Electric fuel pumps contain a check valve to prevent the fuel from draining back into the tank. However, if dirt and rust get caught in the check valve, you’ll experience much longer cranking times as the fuel pump must build up pressure from scratch.

Also, when fuel drains down to the tank, the remaining fuel is no longer under pressure, so it’s vulnerable to causing vapor lock.

Testing for leak-down

When the check valve fails, the fuel rail loses pressure. All fuel rails lose some pressure immediately after engine shutdown, but the remaining pressure should remain steady after 5-mins. To be within spec, fuel rail pressure should never fall below 20-psi within 20-mins after shutdown.

©, 2018 Rick Muscoplat

Posted on by Rick Muscoplat



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