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Jerry
Jerry, Master Mechanic
Category: Dodge
Satisfied Customers: 1751
Experience:  ASE Master tech, 30 years exp. troubleshooter, driveability tech
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Not getting constant power to fuel pump, fuses good, changed

Customer Question

not getting constant power to fuel pump, fuses good, changed relay, new fuel pump. Initial problem was driving and engine just died. 10 minutes later started again and drove 3 miles and engine died. Initially, I checked both fuses and relay and noticed no sound from fuel pump when I turned the ignition on so I replaced fuel pump, didn't fix the problem. Only occasionally the power will get to fuel pump, will run for a few minutes then die. Where is the best place to check? 2000 Dodge 1500 Van. Walter
Submitted: 9 months ago.
Category: Dodge
Expert:  Wayne Crawford replied 9 months ago.

Hello. My name is ***** ***** I will be helping you today.

I see that you have replaced some stuff but I dont see where you tested anything.

DID you test anything?

Customer: replied 9 months ago.
What could I test?
Customer: replied 9 months ago.
I feel like it's electrical but not sure where to go after fuses and relay?
Customer: replied 9 months ago.
I thought that the fuel gauge was separate from the fuel pump but both won't work.
Expert:  Wayne Crawford replied 9 months ago.

Can you get to the wiring at the pump? Thats where you need to test.

Customer: replied 9 months ago.
After realizing the new fuel pump wasn't the problem, I dropped the tank down, took off the electrical connection and hooked it to the old fuel pump to see if it would work. About every 5 minutes I would get temporary power to the pump and you could hear the pump running and the fuel gauge would work also then it would stop suddenly. So I know I am getting occasional power at the fuel pump.
Expert:  Wayne Crawford replied 9 months ago.

Are you getting occasional power or occasional ground?

Two very different problems with exactly the same symptoms.

Customer: replied 9 months ago.
It can run perfectly for a few minutes then dies. That I don't know, can I ground it with a jumper or check what's coming out of the plug itself? I think there are 4 contacts inside the plug, not sure which does what.
Customer: replied 9 months ago.
How do you tell the difference between occasional power or ground?
Customer: replied 9 months ago.
Gut feeling would think ground problem
Expert:  Wayne Crawford replied 9 months ago.

My gut feeling is you got a pump at autozone but Im sure youre tired of trying stuff without testing so we will test it.

Again I ask can you access the wiring at the pump.

Customer: replied 9 months ago.
Expert:  Wayne Crawford replied 9 months ago.

Do you have a multimeter?

Customer: replied 9 months ago.
I do
Expert:  Wayne Crawford replied 9 months ago.

OK. Backprobe the dark green wire with your red meter probe and the solid black one with your black meter lead and start it.

You should see voltage. Watch your meter while it runs till it dies.

When it dies you should lose voltage. If you dont the pump is bad.

Customer: replied 9 months ago.
The instructions I get from you, I won't be able to try until I get off work this afternoon so please fill me with as much info as possible! I'm not sure if I can contact you with this problem after this session, not sure how this works, just tried for 1st time. If I don't have voltage, then what?
Expert:  Wayne Crawford replied 9 months ago.

For what its worth the sending unit gets its power from the PCM wheres the pump gets its power from a relay and ground from the chassis. There is no real direct link between the two.

Expert:  Wayne Crawford replied 9 months ago.

You can contact me back after you try it. Im not much of a guesser.

To contact me after you test it just bookmark this page and return to it.

Customer: replied 9 months ago.
I was only trying to get the old fuel pump to work sitting on the ground, just enough room to get wiring harness off the tank, dropped just enough to do that. Wiring not long enough to drop tank on ground and test. I can rehook harness while suspended to see if it will start but not enough room to check with meter.
Customer: replied 9 months ago.
can't i just check at harness with meter to see if voltage is getting there? I will contact you later, thanks.
Expert:  Wayne Crawford replied 9 months ago.

You can. But you wont know if it would run hooked up without it being hooked up.

If you want accurate test results you need to test it when its not working. WHen its working nothing will test bad.