View Full Version : Fuel pressure and surging question

07-22-2006, 04:10 PM
Just was wondering what kind of fuel pressure you guys are running on something with stock injectors? I have been having this problem when the boost is up to about 14-15 PSI as the car starts surging/stuttering. It runs fine up to that point, and then gives me probs. When I had about 43-45 PSI fuel, it would do this at 12-13 boost, but I increased to about 50 FP and it now does it at 14-15 boost. I dont want to turn up the FP too much higher unless it is safe as I do not have a scan tool for a hotair.

FYI, I just changed the following: fuel filter and double checked the direction of it, wires and plugs, and had to replace a rubber hose in the tank from the fuel pump to the plate. The only thing I didnt do was replace the fuel pump, it was an aftermarket one the previous owner had installed, but the car sat for year, so maybe I should have changed it? ANyways, any help is appreciated.

07-22-2006, 06:13 PM
Any idea what pump it is, or how old it may be?

Have a fuel pressure gauge? One that can be run while the car is in use?

07-22-2006, 07:36 PM
the pump is at least 4-5 years old, not sure brand. I am gonna buy a gauge I can mount on the windshield while driving. The one I got I depress the brake and build boost to about 5-8 psi and it goes up accordingly in FP, but of course I cant see what happens at 14-15 psi. Thanks.

07-25-2006, 12:38 AM
The guy I bought it from said the guy he bought it from had put an ATR pump in there. Anyways, he posts regularly on turbobuick.com and I saw an old post he posted about the same issue from several years ago. He had this problem when he tried to increase the fuel pressure at normal settings, but he had said it ran fine at 30 PSI. So I decided to try it, but cautiously. It seems to run real good now, but I am afraid it might be running too lean. I do not have a scan tool for a hotair yet, so I am not sure if it is knocking, but it definitely doesnt feel like it. It has a kirban fuel pressure guage, maybe it is bad? Any advice is welcome.

07-25-2006, 08:25 AM
but he had said it ran fine at 30 PSI
That is awfully low. Something in the mid 40's would be what I'd expect. Perhaps the pump is bad, or the gauge is bad.

07-26-2006, 03:07 AM
Yeah tell me about, that is what I thought too. But it runs really well at that FP setting. I am not sure how it "feels" in comparison to other hotairs ( since my 84 isnt running yet) but it seems real fast. Not quite as fast as my 87, but not too far behind. I am leaning toward a bad guage, but the guy stated he had the same issue when he bought the guage brand new. In his original post, he didnt receive an answer from anybody and the post ended in '01. Here is the link, if I am allowed to post it here: