View Full Version : AFPR not letting me adjust the Fuel Pressure
05-06-2011, 12:54 PM
I have a 91 k1500 with TBI 350. I purchased the fuel pressure test port from EBay that screws into the back of the throttle body and also installed a JET adjustable fuel pressure regulator only because I got it for almost free. I installed the fuel pressure test port so I could note where the fuel pressure was before I installed the regulator. It was set at about 9-10. When I installed the adjustable fuel pressure regulator it was at about 11. I made a small adjustment to the regulator and it bumped it all the way up to about 18. I dont know if my gauge is reading right but no matter what adjustment it makes it doesnt change the fuel pressure. even if i go all the way from one side to the other. It is also a pain because i have to remove the top of the throttle body and turn the bottom of the pressure regulator with an allen key to adjust it. I have drove the truck since installing these parts and it seems to run very good but I am kind of scared to keep driving it if it actually has 18lbs of fuel pressure because i think it may cause the pump to fail prematurely? I dont know if my gauge is just not reading accurately or what because I have done a lot of research and eveyone says for a mostly stock TBI 350 they run the best around 14 or 14.5 lbs of fuel pressure. I would think it would be running bad because of all the fuel it is getting at 18psi. All I have on my engine is an edelbrock intake manifold and dual exhaust with the stock manifolds and a k&n open element air filter. Any help is appreciated. I would also like to find an adjustable fuel pressure regulator that I can adjust without removing the upper portion of the throttle body to adjust fuel pressure.
05-06-2011, 03:39 PM
Incase it matters, the fuel pressure regulator is Jet part # 61500. Also adjusting the pressure regulator which way is to lower the pressure and which is to raise the pressure? No matter what way I turn it, the pressure does not seem to change according to my gauge.
05-06-2011, 03:47 PM
I don't know why that you can't adjust your FP but you can enlarge the opening under the regulator(on the tbi body) with a die grinder enough that you can get an allen wrench in there without removing the injector pod. I would also try a different fuel gauge to make sure that it isn't the gauge malfunctioning.
05-06-2011, 03:49 PM
Ya, thats what I was thinking. I also called Jet and they said the spring in the regulator may not be seated all the way down. I never thought about grinding the part of the throttle body under the regulator.
05-06-2011, 03:53 PM
Just be sure not to grind it so large that the foam dust seal doesn't go around the opening correctly.
05-06-2011, 04:12 PM
Ya I probably wont even worry about that yet. I just wanna get the fuel pressure adjusted right first.
but I am kind of scared to keep driving it if it actually has 18lbs of fuel pressure because i think it may cause the pump to fail prematurely?
Maybe your 20 year old factory pump isn't up to par for 18psi? Consider getting a delphi TPI or vortec pump (70psi). An FE0114 is $60 shipped. The pump module design is identical...
Running the injectors at higher pressure won't [shouldn't?] cause the pump to fail, but if the pump does start to wear out after you've tuned for 18psi, you'll go lean and your engine may fail prematurely...
05-07-2011, 10:43 AM
adjusting the pressure regulator which way is to lower the pressure and which is to raise the pressure?
Looking at the regulator (from under) clockwise lowers the pressure.
Sounds like a spring problem (overtightened?) & your pump is running at it's max, 18psi is pretty good for a stock tbi pump.
05-09-2011, 01:00 PM
I haven't got a chance to take the regulator back off but today after work I might if its not raining or cold out like it is now. The pump that is in my truck is nowhere near 20 years old. It was replaced about 2 years ago. I just want to turn the pressure down to where eveyone says the tbi motors run the best. It seems to be running good right now but the gauge reads 18 no matter what so I am going to take the regulator back out and make sure the spring is seated properly and if it is I am going to try another fuel pressure gauge.
1988 GMC 355
05-09-2011, 02:17 PM
Did you use JET'S spring in the regulator or your stock spring?
05-09-2011, 02:18 PM
The regulator did not come with a spring so I used the stock one.
1988 GMC 355
05-09-2011, 02:22 PM
hmm ok well thats really wierd then. I would pull it off and make sure everything is seated right. then I would swap guages to verify your guage isnt bad.
05-09-2011, 03:42 PM
Ya thats what I am gonna do. I called Jet and they said if the spring isn't seated in the regulator correctly then it will cause similar problems. And ya if that doesn't fix it, i am going to try another gauge to varify mine isn't reading incorrectly.
1988 GMC 355
05-09-2011, 08:37 PM
let us know, then we can try to help more
05-09-2011, 10:35 PM
fpr must be placed in return line after tbi
is orriginall oem fpr still in tbi?
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