Fuel pump issues (Page 1/3)
tnkgnr OCT 21, 11:18 PM
Hey there,

I have an 86 3.4pr and have been blowing fuel pump fuses somethin fierce. I got a new pump, new strainer, new fuel filter and swapped everything out no problem. The system charges to 40 odd psi as it should. The interior of the tank was pristine - no rust or particles.

Thing is, since I swapped the pump, it's had what I think is an unacceptable whine to it...as if it's struggling to do its job (but the whine doesn't increase with load on the engine). Seems like the car has diminished oomph at high RPMs. After about a week of doing perhaps five trips, tonight the fuse blew again for the first time since changing everything as I was taking off in first gear.

Any ideas what the problem could be? I reused the old pulsator when changing - that shouldn't be a problem right? When I had everything out, I made sure to check all the wire insulation from the sending unit to the firewall for any potential shorts, but didn't see any evidence that was a problem.
Warlordsix OCT 22, 08:11 AM
You typically don't need the pulsator with most modern pumps. If you have a turbine-style pump, and you probably now do, it runs quieter than the older gerotor pumps, draws less current and doesn't produce the varying pulsations that required use of pulsators with the older, gerotor pumps.

Ernie

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'87 Fiero 4.9 5-speed

tnkgnr OCT 24, 02:23 PM
Yea, but having a pulsator, even with the turbine-style fuel pump that is there now, shouldn't make you blow fuses right? There's no way to hook it (pulsator) up backwards, correct?
fierosound OCT 24, 03:16 PM
Check the vent line on the tank.
If it's blocked, pump is creating a vacuum in the tank.

See Section 6C in Factory Service Manual.
Can be checked without dropping tank.

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My World of Wheels Winners (Click on links below)

3.4L Supercharged 87 GT and Super Duty 4 Indy #163

[This message has been edited by fierosound (edited 10-24-2020).]

tnkgnr NOV 09, 04:23 PM
Did the evap line test and it works properly (blew in lower hose - not able to push air, applied vacuum to upper hose and then was able to blow through lower hose). I also applied vacuum to steel fuel vent line, and then was able to release it by opening the gas cap, so there's no blockage.

Guess it's dropping the tank again for me...unless there are any other ideas out there.
tnkgnr NOV 09, 05:39 PM
I jacked it up to look around and I think I may see a problem. Is it possible to pinch a line by tightening the straps too much? Notice the gap between the center brace and the gas tank in this pic.
Patrick NOV 09, 06:02 PM

quote
Originally posted by tnkgnr:

Is it possible to pinch a line by tightening the straps too much?



None of the rubber fuel lines are located under or on top of the tank.
tnkgnr NOV 09, 06:05 PM
I was thinking the solid ones could also get crushed?
Patrick NOV 09, 07:34 PM

quote
Originally posted by tnkgnr:

I was thinking the solid ones could also get crushed?



Not if each one was located correctly in its "track".

In any case, the tank only goes up so far, and "over tightening" of the straps wouldn't move the tank up any higher.


quote
Originally posted by tnkgnr:

Any ideas what the problem could be? I reused the old pulsator when changing - that shouldn't be a problem right?



Well, there's a good chance that this pulsator is 34 years old. Perhaps it doesn't seal as effectively as it used to, and the fuel pump is spinning like crazy (because of less load) due to fuel leaking past the pulsator/pipe connections. How quickly does the fuel pressure drop when the engine is turned off? I wager it drops very quickly.

[This message has been edited by Patrick (edited 11-09-2020).]

tnkgnr NOV 09, 08:51 PM
Yea, they were all in the tracks correctly.

It does drop off quickly. I've verified that it's not the injectors leaking. Guess I'll just drop this thing and replace the pulsator with some submersible fuel line.