Changed filter, pump, and regulator, but it still has only 30 psi with key on, and drops to 26 or 27 at ideal. Any ideas?
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05-14-2013
Changed filter, pump, and regulator, but it still has only 30 psi with key on, and drops to 26 or 27 at ideal. Any ideas?
Originally Posted by W-Body Store
05-21-2013
I called Grand Auto, the people who have the resistor kit. They said it was for NO, fuel pressure, not LOW fuel pressure. Plus, their service manager was a JERK
05-21-2013
Who knows these cars? Don't trust dealers.
05-21-2013
do this to your relay in the fuse box under the hood, if all is better, the resistor is bad, its in the fender by the battery.
05-21-2013
Ok.. who has a clue what the resistor does? Cause it's not looking like it from this thread.
The resistor is only used when the car is running and below X throttle threshold. It is not used for priming and starting. It is not used at wide open throttle.
The resistor should not causing a low fuel pressure issue.
05-21-2013
Por..I would test pressure coming out of the tank at the filter. If you can build pressure there, then likely the FPR "should" be bad.
05-21-2013
I would also lean towards your FPR.
05-21-2013
I have a piece of a fuel rail that is attached to a piece of hose to go on my fuel pressure tester for this test. The key here is.. does the fuel pump build pressure and how fast does it leak down if it will build pressure. It should hold pressure for 10 minutes according to GM
05-22-2013
Brand new fuel pump and FPR
05-22-2013
Even with the new pump and FPR, I have 30psi at the key, it then drops to 25. Starts fine, and usually goes up to 35 when I accelerate. I clamped off the return line and can get 50 plus. I have tried 2 different FPRs
05-22-2013
Never heard of new parts going bad? I have seen new pieces be bad. It's not common, happens though.
Since you changed the pump, filter and regulator, now it's time to diagnose each step of the fuel system one by one to figure out why you have low pressure.
Test the pump to filter (I do this at the supply hose to filter connection point)
Should show you that the pump is capable of building pressure and holding it.
I would also test the voltage at the pump at this time.
Test pressure after filter (I do this at the supply line to fuel rail connection point)
Proves that the filter isn't clogged or causing a restriction and neither is the supply line coming up the car from the tank/filter.
Test pressure with FPR on the rail (schrader valve on rail)
Proves out that the FPR is doing it's job.
If all those check out, then it's not a pressure or pressure holding issue, it's a volume issue. You can have pressure build up and hold w/o having enough volume. Once you start the engine and fuel is needed, pressure would automatically drop if there is no volume to maintain the needed supply.
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