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.
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.
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?
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.
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.
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.
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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).]
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.
All right, new pump/strainer installed and running. Will start driving it tomorrow and we'll see if the fuses keep popping. I ordered up a Bosch one this time...was pretty nervous since the polarity appears reversed from the original.
Popped another fuse on the short test drive. Again while taking off in first gear. I disconnected the supply line at the fuel rail and primed the pump - when I did so, the pump was nearly silent...so I'm thinking maybe some sort of obstruction might be in there?
With the return line disconnected, the pump still makes the loud noise and the pressure spikes to near 80psi. The fuel does come out of the return line, but more of a very quick dribble vice the flow from the supply line.
I guess this test confirms that the issue is somewhere in the fuel rail (I suspect the pressure regulator, which should be here tomorrow).
All right - got the new pressure regulator housing in today and installed it along with a new regulator. When primed it gets to just over 40psi, while idling it's just over 30psi. When I rev the engine it briefly spikes up just over 40psi.
The obnoxious sound has completely gone away, which is great, but the original problem still remains as my test drive blew multiple fuel pump fuses.
Anyone have any ideas? I suspect with an essentially new fuel system throughout there must be a short somewhere that is triggered when I torque the engine (I have installed new motor mounts after developing this problem). I've grabbed and moved the firewall harnesses with the engine running to simulate movement but can't replicate the problem. HELP! What would possibly blow this fuse??
Inspired by posts from 2.5 and Old Lar, I checked the wires over by the relays to wire harness area. Sure enough, I seem to have the same problem where the insulation on the wires was rubbed off from a heat shield.
In my instance the exhaust pipe head shield melted through the plastic covering and then where the shield is stamped together making an edge it cut through the wire insulation. Hoping that fixing this will resolve my issue!
I've removed the portion that was melted in these pics (from above you wouldn't see it, as the top looked normal).
Oof...just did a fuel pressure test - nearly 80psi! Maybe the fuel pressure regulator?
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Originally posted by tnkgnr:
Sigh...got the part and go to replace it and see this - looks like some sort of adjustable regulator, and the new valve doesn't fit that housing.
Glad you got the problem sorted out with the wiring... but that was pretty weird with the fuel pressure regulator. I wonder why someone would consider doubling the specified fuel pressure?
Glad you got the problem sorted out with the wiring... but that was pretty weird with the fuel pressure regulator. I wonder why someone would consider doubling the specified fuel pressure?
I think it might have just been a coincidental failing regulator since I had checked the fuel pressure before and it was appropriately at 40psi. When I started all this, there was no abnormal sound from the fuel pump, but as I got to tearing things apart, the sound began when I put a new pump in and the fuel pressure check at that point was the 80psi. Maybe in the process of disconnecting and reconnecting everything, some small piece of debris got stuck in there?
Maybe in the process of disconnecting and reconnecting everything, some small piece of debris got stuck in there?
And doubled the fuel pressure? I don't know how that would be possible... but in the almost 50 years I've worked on my cars, I've never had to mess around with a fuel pressure regulator... so it's quite possibly beyond my scope of expertise.
[This message has been edited by Patrick (edited 01-01-2021).]
I think we can conclude the pressure issue was directly related to the regulator - just don't know why. The fact that the pressure was initially okay means that it was not initially set wrong (I never even knew it was adjustable until I removed it).
The hole that the regulator sits on is maybe 4mm in diameter. Since pressure = force/area, if half that hole was covered it would double the pressure. Not saying that's what happened (especially since I didn't see anything when I removed it), but it's plausible. Another option is that since that old regulator was so crusty, maybe it just seized up and required twice as much force to move it?
I don't even know where the adjustable one came from - couldn't find anything like it in searches. Looks nothing like the Fiero Store one.