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TBI 350 fuel pressure...

CK5

CK5

In my underwear
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My 1989ish 350 TBI has no power and just bogs down at WOT.
I put a fuel pressure gauge on it and it's pulling 8 PSI at idle, WOT while driving it stays at 8 PSI.
Went back and pinched the return line, it moved up to 12 PSI, WOT while driving it goes down to 10 PSI.

Any ideas? Seems like it might be the regulator?
 
8-9 was realistic in the day . But they like / love 11-15 psi much more . So try and get it up . Otherwise its been so long i got no clue .

Also how old the fuel filter ? If old and dirty it can restric flow bad .

And shouldn't be pinching them braided steel lines .
 
Fuel filter is a few hours old, replaced it right before test drive. Pinched a rubber hose part of the line.
 
Iirc GM's spec was 9-13. Some have reported noticeable issues even at 9PSI however.

Mine stumbled and ran like garbage randomly (probably related to fuel level) when the fuel hose was split in the tank. Fuel pressure went to 0 immediately upon engine shut down, and it should not.
 
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dyeager535 said:
Iirc GM's spec was 9-13. Some have reported noticeable issues even at 9PSI however.

Mine stumbled and ran like garbage randomly (probably related to fuel level) when the fuel hose was split in the tank. Fuel pressure went to 0 immediately upon engine shut down, and it should not.
Click to expand...

FWIW, the "fuel bleed down" check can be done with the fuel pump prime cycle, you don't actually have to start/stop the engine to check if it holds pressure or not.
 
I've experienced the split hose, where pressure never got above 2-3psi. I've also had a pump that leaked down. The running pressure was fine, but it bled off in under a minute of key off.
 
So, I have the tank on empty ready for me to find the time to drop it. I might also have a bad fuel sender as it's empty and showing a 1/4 tank, it has always been like that, way past full when full and never going below a 1/4 tank, maybe I can kill two birds with one stone. Thoughts?
 
Electrical geniuses can offer insight, but I would expect there to be a resistance or float arm issue.

My experience with the sender/gauges is that if the sender goes bad, it's the rheostat, which leads to all sorts of weirdness.

Always reading above the correct level means the gauge is seeing consistent resistance different than what it should be across the entire sweep of the float arm/rheostat. I'd take the tank out, leave the sender/wiring connected and manually manipulate the float to see if you can get the gauge to read empty. If yes, I'd probably then look at bending the float arm to get the gauge to read correct on E.

It is possible the fuel gauge was swapped and/or the resistor on the back of the gauge is bad. Neither I'd expect would be the cause of the issue you describe.
 
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