I replaced this around new years but since then I'm curious, is this thing adjustable? Is that what the tork screw in the middle is for? Do you turn it clockwise for more and counter for less pressure? I remember turning that a little before I installed it the next day.

 

What year and engine do you have? What is your KOEO pump running fuel pressure? Some regulators are adjustable, if yours has a torx screw, that's what it's for. It is set at the factory and adjustment is not recommended. If fuel pressure is out of spec, replace it.

 

93 4.3 w code. what does koeo mean? can i take the plenum off and adjust it? pressure key on only is 48-50. Running is 40 to 50.

 

KOEO = Key ON Engine OFF.

GM does not publish any "engine running" fuel pressure specs for your engine, there are way too many variables involved.

Fuel pressure on your 93 W: Key ON, engine OFF, fuel pump running, pressure must be 55psi to 61psi. It must remain above 50psi for at least 10 minutes. If it fails one or both of these tests, it means there is a problem with fuel delivery and more testing is necessary to determine what the problem is.

Your reading of 48-50 is too low. If that's the maximum that the pump can build, adjusting the regulator will do nothing. First you need to check maximum pump output pressure at the fuel filter. All pressure and fuel flow must end at the pressure tester. Gonna take a little "creative plumbing" on your part Max pressure, while the pump is running, should be ~70psi to 100psi and must remain above 50psi for at least 10 minutes. The results of this test will tell where to look for the problem.

 

Yes that torx adjusts it. You want to crank it up to at least 58... 62 is best

 

I replaced the fuel filter with one from a volvo xt90. The filter and lines to it were so badly rusted that I coulnd't break them free. The nuts on the steel lines rounded off so I cut the whole section out and replaced it based on info from this forum. If the pump is supposed to push out 70-100 psi and I'm only reading 48-50 at the valve at the back of the plenum, wouldn't that automatically suggest the pump is weak and not working correctly? Is it worth dropping the tank and checking the sock or I believe I read that there is a plastic line inside the tank that can crack?

 

Low regulated pressure, which is what you have, means there is a problem, that's all. Replacing any parts at this point is strictly a guess.

Testing pressure at the service port indicates whichever is lower: regulated pressure or maximum pump output pressure. If the reading is not within specs, (yours is not) it does not tell you what the problem is, only that a problem exists. Maximum pump output pressure must be tested at the fuel filter to determine if the pump is supplying the proper pressure to the fuel pressure regulator. If the pump is within specs, the problem is inside the plenum.

 

Well plumbing wasn't that hard since I have rubber fuel line on either side of the filter I installed. KOEO pressure started at 80psi and fell to 51psi after ten minutes. Bairly within specs. If the pump isn't the problem then why would I get such erratic pressure at the plenum? Thanks for the help on this one Captain.

 

Your max pressure and leakdown are acceptable and the pump is not the problem. The problem is in the plenum.

KOEO at the service port, 48psi to 50psi is too low. We need to know what the pressure is 10 minutes after the pump shuts. The results will tell if the regulator is set too low or if there's a leak.

 

I will reconnect the fuel line tomorrow and recheck pressure at the plenum. I am taking tonight off after a face full of gas.