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View Full Version : Weak/dying fuel pump? 80psi with return clamped.


Darkwolf
07-21-2011, 10:31 AM
http://www.turbo-mopar.com/forums/showthread.php?12355-How-to-diagnose-a-bad-fuel-pump-or-FPR.-added

Using that I did the 12v to the plus terminal of the coil with the return line clamped. First time I did it I got 100+psi and I release the pressure. Second and every other time I did it the pressure was 80psi and that was the highest I could get with repeated tries. I know I had a good clamp on the return line since the pressure held steady after I disconnected the power to the coil.

The van runs fine at idle but put it under a load and it struggles to run and dies. The best I can tell without running myself over the fuel pressure drops when it stumbles under load. Before I go spend the money just want to make sure my diagnoses is correct and I need a new fuel pump.
PunKid
07-21-2011, 10:43 AM
Tape the fuel pressure gage to the windshield and take it for a drive
Darkwolf
07-21-2011, 11:18 AM
Hose isn't long enough to do that. I just chocked the wheels and put the parking brake on. It is pretty much not drivable at this point too. I was lucky I was close to home when it started doing it. I was barely able to get it up a slight incline in my drive way when I went to move it when I tried after getting home.
cordes
07-21-2011, 01:06 PM
80PSI is a sign of a dying pump IMO. That's about the most that a TBI pump will make new, and that's not enough to get the job done.
turbovanmanČ
07-21-2011, 01:52 PM
Your pump is dying. Did you check volume?

Cordes, depends what year TBI pump as some are turbo pumps, the other years, you'd be lucky to get 30 psi out of them.
cordes
07-22-2011, 12:32 AM
Your pump is dying. Did you check volume?

Cordes, depends what year TBI pump as some are turbo pumps, the other years, you'd be lucky to get 30 psi out of them.

I thought they needed more pressure than that. What year TBI pumps are you talking about? I'm not familiar with the much earlier TBI setups too much.
Darkwolf
07-22-2011, 12:51 AM
I did not check the volume.
turbovanmanČ
07-22-2011, 01:03 AM
I thought they needed more pressure than that. What year TBI pumps are you talking about? I'm not familiar with the much earlier TBI setups too much.

Pre 90 I believe were only put out 15 psi at the injector, later went up to 20 psi.


I did not check the volume.

That's another indication of how well a pump is doing.
Ondonti
07-22-2011, 04:47 AM
My 1994 pump has the relief crack open at 80 psi.