Fuel pump issues (Page 3/3)
tnkgnr DEC 31, 04:50 PM
Confirmed with a nice aggressive test drive. Problem fixed!
Patrick DEC 31, 10:35 PM

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Originally posted by tnkgnr:

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?
tnkgnr JAN 01, 03:01 PM

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Originally posted by Patrick:

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?
Patrick JAN 01, 03:57 PM

quote
Originally posted by tnkgnr:

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).]

tnkgnr JAN 01, 04:38 PM
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.