Prime Your Skills to Tackle Electric Fuel Pump Trouble

You’re embroiled in a poor performance or no-start diagnosis. Could it be the fuel pump? Could it be the pump relay?


A defective pump check valve can cause a hard-start problem. Check the operation of the pump's check valve by watching the rate of pressure drop after turning the ignition off. Compare the drop to specifications. If the drop-off rate is quicker than specified, the check valve may be bad. Most check valves are integral with the pump and can't be replaced by themselves. Replace the pump.

CAUSES OF PUMP FAILURE

Electric fuel pumps are dependable; compared to their mechanical predecessors, they fail less often. But like any part, they can go bad.

Water can ruin a pump. The pump is capable of passing water without affecting it much, but water in the tank when the vehicle is stored can destroy the pump.

Another cause of pump failure is a restricted filter sock/strainer on the pump inlet. Dirt can build up on the filter and eventually burn out the pump from fuel starvation. Even a strainer that looks OK can be misleading when it’s restricted with fine contaminants from the tank.

On multiple pump systems, a bad low-pressure, in-tank pump can damage the high-pressure pump from fuel starvation. If you replace the low-pressure pump, make sure the high-pressure pump is okay when you're done.

Of course, pumps eventually just wear out because of leaking seals, excessive clearances and motor failure. Even the best pumps don’t last forever and reach the end of their useful life.

TIPS FOR A CHANGE

When replacing the pump, always replace the strainer at the same time. It’s not worth the risk of a comeback to skip this step.

While most in-tank pump replacements require dropping the fuel tank, this is not always the case. Some vehicles have access panels so you can get to the pump easily. The key thing is to know this before you drop the tank.

The bottom line is, when it comes to electric fuel pumps, don’t jump to the pump until you’ve checked the rest of the circuit.

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