Electric Fuel Pump Testing

by Mike Gensler and Al Brase

Can you bench test a fuel pump by hooking up a 12 volt battery to the +/- on the pump?

Mike Gensler writes:

Yes you can bench test them. It's not good to run them for more than a second or 2 with no gas because they are actually gas cooled and lubricated. But you can touch power to them briefly to make sure they at least turn.

Sometimes you can resurrect a 'stuck' pump just by whacking it once or twice with a piece of wood (don't hit it hard enough to dent it!!).

If you are going to bench test it with gasoline running through it, you need to remember that these are 'push' pumps, not 'pull' pumps. So you need your gas source to be able to gravity-feed the pump. And also bear in mind that these are high pressure, high volume pumps so make sure the output hose is safely secured. These pumps will move around a lot while running so clamp it down to your bench before firing it up. Try to minimize sparks when you hook up the power source!! Probably the best way is to install a simple 12V on/off switch and secure all the wires. You really don't like to see sparks flying around when you're messing with gasoline. Gas fumes are at least as flammable as the liquid so do all of the above in a VENTILATED area and always have a fire extinguisher handy just in case. Be safe.

Al Brase writes:

I've found very often that when a fuel pump won't run it has debris lodged in it, apparently. I've usually been able to dislodge or unlock a locked up pump by hooking up the wires in reverse an actuating the flapper a few times, maybe as many as ten times. I've never found a pump that I couldn't free up like this. Maybe good to know if you're stuck out in the boonies. Even if you've a spare, changing one is not a pleasant job (always a danger of a gasoline bath).

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