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Discussion Starter · #1 ·
OK, so im reasonably sure that my fuel pump is dead. Its given me problems for a full year off and on.

Anyways, from what i can gather through searches, you can test fuel pumps with a 12v (or is it 9v?) power source. There are the two leads coming off of the pump, a red and black wire, which i assume are pos and neg.

Can I tell if the pump is dead by hooking it up to a 12v source (car battery?) or a 9v (9v batt) and listening for that whine it makes?


If that isnt how to test the pump then how should i?
 

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Its 12V. Theres nothing on a truck thats 9V.

The proper way is to test the fuel pressure at the rail. There is a schrader valve on it, and you hook the gauge to it. It should be ~40psi. Haynes will have the proper procedure to test it.
 

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Discussion Starter · #3 ·
OK so if you put 12v across these things they should fire right up and start making noise?

The reason I ask is that i have two pumps here, one is the one that was in the truck, the other is brand new today. I went to test the new one with a 12v batt. and i didnt quite get what i was looking for. When i made the connection all i got was a weak thud from the inside of the pump that sounded like something moving, but only very briefly and then it was gone. It certainly didnt give me the high pitched whine i was expecting.
 

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I wouldnt run the pump outside of the tank. The fuel lubricates and cools the pump.

You may have fubared the new pump, but I would just take it back and say it doesnt work and get a new one. This time, install it, then test it.

Or better yet, use a voltmeter to test for 12V at the connection on the truck.
 

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Discussion Starter · #6 ·
i cant see a really brief test burning a pump out, if it generated thatmuch heat that quickly no way in hell would it be safe in a tank full of gas.
 

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Discussion Starter · #8 ·
wow looks like i have two dead pumps then. I tried putting 12v to both of them from a battery and neither ran at all. There was a faint noise from each, but it was only for a split second and it didnt sound like the pumps usually do.
 

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Satyr of the Midwest
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I wouldn't worry too much about the sound. Remember, it's usually in a liquid-filled, thin-walled metal box when you hear it, and even then it's usually pretty quiet. Are you sure you've got +12V getting to the pumps, i.e. is your battery good, and are the leads you're using good?
 
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