Fuel pump loses power 3-6 secs after car turns on.

[95AWD6Bolt]

I just replaced my timing belt with the help of a friend and when we went to start my car it started fine but it dies 3-6 secs after it get sstarted. We started checking around and found that the fuel pump lost all power after the car is turned on. My friend somehow hardwired the pump with an alligator clip temporarily so that when connected the pump is always on. When he did that, it ran fine. We are now researching to find out what is wrong, anyone have any suggestions??

Also, later that night, I connected the pump and it started and ran, but after about 20-30 secs, i started getting a check engine light and the car would die out. I havent gotten a chance to attempt to pull that code yet.

Mods are in my profile, i have a rewired 255 lph fuel pump.

 

[BluFalcon]

Check the relay you used when you rewired the fuel pump.

It might be faulty, or not designed to operate constantly. I had a rewired pump on one of my GVR4's, and it would randomly die out on me. Finally traced the problem to the relay I used. Swapped it out for a new relay, and never had it happen again. I'm not saying that's going to fix your problem, but it'd probably be a good place to look since the car ran with the relay bypassed.

 

[yokotabrat]

Could be a damaged ecu. The fuel pump is activated first by the starter relay and then by the ecu via the MPI relay. If the ecu doesn't pull pin 56 low, the portion of the MPI relay that provides power to the fuel pump turns off after the car starts. When the caps leak, it tends to destroy the trace that goes to pin 56. You can verify this by measuring the voltage at the ecu at pin 56. If you measure battery voltage all the time, the ecu isn't sending the signal to the MPI relay to keep the fuel pump activated. Hope this helps.

 

[luv2rallye]

+1 above.
Excellent description. I'd only add that you can get at that white w/red stripe wire on pin 7 of your 10 pin MPI/FP relay also.

 

[dirtygermankid]

Hey guys..

I'm the one doing the work on the car...


The relay is fine. I tested the relay.. and determined the problem to be within whatever controls the power to the fuel pump when the car is on. The car will run great when the pump is connected directly to a constant 12v source, but that's no solution.

I'll test his ECU when he comes back from school.. are there any other relays that control the fuel pump, and where are they located? I got a service manual.. I'll go through that when until i figure it out.


Thanks for the tips.