Thurston Car Talk: Fuel Pump Failure

Submitted by Bron at Bron’s Automotive

Do you know why those expensive electric in-tank fuel pumps usually fail?  There are two main reasons, both of which we can control.

First, electric fuel pumps are lubricated by the fuel they pump, and cooled by the fuel they are immersed in.  One of the worst things we can do to a fuel pump is to run out of gas. It hurts the pump to run dry.

Some mechanics suggest never going below ¼ tank of fuel because then the fuel pump is always sitting covered in cool fuel.   The driver is in direct control of the fuel level.  Don’t wait for the low fuel reminder to come on to pull up to the pump!

The second thing that ruins electric fuel pumps is a plugged fuel filter.  At Bron’s Automotive, we always replace the fuel filter when we replace a defective fuel pump.  About 95% of the time the filter is badly plugged, and the cause of the pump failure.

The reason a plugged filter burns up a fuel pump is simple:  An electric pump will draw whatever current it needs to get the job done.  We normally see a pump draw 1 to 1.5 amps with a functioning filter.  When the filter is plugged, the pump can draw up to 7 amps to push fuel through it, and this excessive current draw simply burns up the brushes and the commutator in the motor.

Changing the external fuel filter at regular service intervals is cheap insurance for your fuel pump.

Some later vehicle models have eliminated the external filter that is located after the fuel pump and rely instead on the pickup screen that is in the tank just before the fuel pump.  These are more tolerant to dirt than the external variety and rarely need changing.

If you can’t remember when you fuel filter was last changed, call us at 943.5993 and we’ll let you know if you have the replaceable type.

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