loosing fuel pressure....need some help!!
Thread Starter
Instructor
Joined: Mar 2002
Posts: 247
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From: las vegas nv
loosing fuel pressure....need some help!!
ok , heres what ive done so far. car is an 85 with 4+3, all stock. was having problems with hard starting, so took off the intake, cleaned up everything. replaced all injectors, rebuilt by cruzin performance. new cold start injector. new fpr from gm. new filter from gm. have put in new plugs and wires, cap, rotor. car now fires right up, but when warm looses fuel pressure at about 2600 rpm. ran it on a dyno to see what was up and its going way lean once you try to put the wood to it above 2600. it started off being intermitant(spelling) and got more consistant. before i changed all this stuff, it ran crappy till it warmed up and then ran great. now just the opposite, runs great cold, when warm, runs crappy. have not changed the fuel pump, and its about the only thing i havnt changed. could the pump go south that quick?? maybe cant keep up with everything flowing well?? suppose its possible i got a bad fpr, will probably change back to the old one to test it.
anyway, what started out as a good major tune up has turned into a head scratcher. anyone have any ideas?? dont think it would go lean if the injectors were leaking, but could be wrong. checked vacuum , no leaks. idles very well, not hunting. baffled here fellas, need some help. thanks, regards, fng
anyway, what started out as a good major tune up has turned into a head scratcher. anyone have any ideas?? dont think it would go lean if the injectors were leaking, but could be wrong. checked vacuum , no leaks. idles very well, not hunting. baffled here fellas, need some help. thanks, regards, fng
Pro
Joined: Sep 2003
Posts: 670
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From: charlotte nc
Re: loosing fuel pressure....need some help!! (FNG)
I'm in the middle of doing the same thing to my 86. I'm waiting for my injectors to arrive. Have you checked the output of the pump. It could be going out. Other than that, I can't think of anything else. Maybe someone else can help. I'll be watching your thread to see how it works out and I hope that I don't run into the same problem. Good Luck!!
Thread Starter
Instructor
Joined: Mar 2002
Posts: 247
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From: las vegas nv
Re: loosing fuel pressure....need some help!! (dwestsr)
havnt checked the pump yet, will do it later this am. what gets me is it ran good when it was warm before i did all this stuff. at first i thought maybe the injectors maybe were bad from sitting around, but the damn thing is lean, not fat. oh well , will get back to it a little later. thanks, fng
Safety Car
Joined: Feb 2002
Posts: 4,212
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From: Sun City West Az
Re: loosing fuel pressure....need some help!! (FNG)
A couple of things. If it is running good in open loop and bad in closed loop, I'd be looking hard at the O2 sensors. When you pulled the intake, did you use sensor friendly sealant? If not, you may have coated your O2's from the off gasing of the sealant and they have become "lazy" causing the lean condidtion. The fp may be going out. You need to hook up a fp guage to the schrader, tape it to the windsield and go for a ride.
Thread Starter
Instructor
Joined: Mar 2002
Posts: 247
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From: las vegas nv
Re: loosing fuel pressure....need some help!! (ittlfly)
thanks for the reply. didnt use any sealer, gaskets had rubber stuff on em. 02 sensor is about a month old. like the idea of putting on the guage and going for a ride!! thaks again. will get this sorted out one way or the other if i have to trash the tpi and put a carb on this bucket. thaks again, regards, fng
Burning Brakes
Joined: Oct 2002
Posts: 983
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From: Bergen County NJ
Re: loosing fuel pressure....need some help!! (FNG)
Sound like you've done a thorough job of eliminating possibilities. Why don't you throw in a new fuel pump relay while your at it. It probably won't make a difference, but it's cheap and won't hurt.
Thread Starter
Instructor
Joined: Mar 2002
Posts: 247
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From: las vegas nv
Re: loosing fuel pressure....need some help!! (sraft)
Why don't you throw in a new fuel pump relay while your at it. It probably won't make a difference, but it's cheap and won't hurt.
just happen to have one sitting on my bench....sure as hell cant hurt. thanks
just happen to have one sitting on my bench....sure as hell cant hurt. thanks
