Fuel Pressure Regulator adjustment? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-18-2009, 04:31 PM   #1
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Default Fuel Pressure Regulator adjustment?

I have a 96 SE. My fuel pressure seemed to be a little low... 38psi turning the key on (not running) and letting the pump run and stop. I talked to a Pontiac Dealer who told me that the correct range on a 96 SE is 40.5 psi to 47 psi with the key in the on position engine not running.

In the center of the FPR is a tamper-proof torx screw. I talked to a mechanic who told me that the screw would adjust the pressure but that the FPR should never have to be adjusted. I carefully tighten the screw and moved the pressure reading on my gauge up to 42-43psi. I just did this last night and the car seems to run better today (no P0171 so far) I am anxious to see if this affects my MPG. I know that I would have been running lean with low pressure but the the PCM would be adjusting the fuel trims higher to compensate.

Everything else like removing the vac line and the pressure going up seemed to be normal both before and after adjusting the FPR..didn't see any gas in vacuum line. I will probably run it this way for a while and see if my old friend Mr P0171 pays me any return visits. Then I may or may not replace the FPR based on what you all think if I did something that could be un-safe etc.

Has anyone else ever done this. Is it safe to do? What might I screw up. Comments welcome!


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Old 09-21-2009, 09:42 PM   #2
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How did you do the adjustment on a tamper-proof torx screw? How much did you turn it?

I assume you had to pull the FPR out.

Everything still working out OK?
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Old 09-21-2009, 10:21 PM   #3
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Quote:
Originally Posted by FaceShot View Post
How did you do the adjustment on a tamper-proof torx screw? How much did you turn it?

I assume you had to pull the FPR out.

Everything still working out OK?
Please, as soon as GM comes out with a new style of bolts to prevent owners from messing with them you can bet someone starts working on making a tool that will work, you can get the security torx bolt bits from autozone
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Old 09-22-2009, 08:26 AM   #4
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Spit.. your fuel pressure looks good and shouldn't be causing the code.

Please see the other thread for more info. But in my experience ... your pressure shouldn't be a problem.
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Old 09-22-2009, 02:43 PM   #5
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I'm not sure that I'm out of the woods yet with P0171. However to answer your questions. A tamper proof torx screw has a little finger that sticks up out of the center of the star. A tamper proof bit is has a like-sized hole in the center of it. (Harbor Freight sells bit sets that includes many types of tamper proof designs.torx, allen/hex, winged) I adjusted it with a pressure guage attached to the fuel rail. turning it clockwise...tighening it, I slowly and carefully increased the pressure reading on my guage. I don't think I turned much more than one to one and a half full turns...to increase it by 4-5 PSI.

I looked at a new FPR at AutoZone and they were non-adjustable....so maybe some O.E. units are too?.

Chances are I have a vacuum leak somewhere. or a bad/dirty ground or battery cable. Although I have driven the car for 3 days...7 or 8 run cycles and the P0171 has not come back...YET. Emphasis on the word yet.


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Old 09-22-2009, 03:46 PM   #6
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LOL, I understand that statement more than you know. Took me close to a month to believe it.
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Old 09-22-2009, 04:32 PM   #7
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Facesshot,

One more thing..no I did not have to remove the FPR. I did have to hold the FPR so it doesn't spin while tightening the torx screw. The FPR is held in place into a cup on the fuel rail with a retaining ring..but it'* sealed with an o-ring and can and will turn/spin...so hold it with one hand and turn the torx with the other.

All that said I am sure that there may be a point where a FPR is so far gone that adjusting won't work. Like a hole in the diaphram or a broken spring..so just be careful. To me it seemed like it must work like a pressure switch on a compressor or a water pump.those too are factory pre-set for pressure and not really intended or recommended to be adjusted..but do-able non the less. Just something you have to do with caution,.

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Old 09-23-2009, 12:04 AM   #8
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Well, I have one word: NUTS. On the '94 there is no torx screw, outside or inside. I had to go buy a new one which did put my in spec and a hole in my wallet.
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