fuel problem
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Senior User
Joined: Sep 2010
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From: State College, PA
fuel problem
Opps, I was reading through some threads on the 1987-96 thread and accidentally posted my question in the wrong thread, but... for the past week or so when I started my truck it sputtered and coughed once or twice then it ran just fine. Then tonight I started it and it ran just fine, but I went out to move it later and it randomly started shaking and sputtering quietly and then shut off. I'm thinking it has to be some sort of fuel issue, but I'm not sure what? Any suggestions?
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From: State College, PA
Still havent diagnosed the issue yet, but a buddy of mine came over last night and checked it out. The truck will turn on and idle still, but it sounds like it has a miss and it idles very low. if you let it idle for a little while or give it gas, you can get the rpms to go up and you can even get the truck to drive, but not very well. I don't know if that helps at all, but any info would be appreciated.
Post Fiend
Joined: Dec 2010
Posts: 10,121
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From: Orrville, Ohio
Try unplugging the ICP sensor and starting it up. Could be a stuck IPR or a bad ICP causing very low HPO pressure to the injectors.
Dangit Ian! you beat me to it.
Dangit Ian! you beat me to it.
Last edited by DIYMechanic; Aug 18, 2011 at 06:49 AM. Reason: Ian types faster than I do!
Post Fiend
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From: Livoina,La
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Senior User
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From: State College, PA
I'll check the ICP. Haven't checked the fuel pressure yet, but I'll do that too. As far as the injectors, I believe their the stock ones, so 118,000 miles. Thanks for the responses, guys, I'll try some stuff and get back to you.
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Senior User
Joined: Sep 2010
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From: State College, PA
I replaced the fuel filter today and that helped a lot. Truck sounds much better than it did before, but its still not perfect. It really struggles at idle and even when you floor it in park, it can only reach about 2100 RPMs. I tried unplugging the ICP sensor, but that didnt make a difference. I havent checked the fuel pressure yet because I'm not sure of the best way of doing it. Should I run a piece of fuel hose to the fuel purge and hook a gauge up to that?
Post Fiend
Joined: Dec 2010
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From: Orrville, Ohio
To check the fuel pressure just use a cheap stick style tire gauge. It will have to be a 75 or 100 lb range gauge, but you can just check it at idle on the Schraeder valve (it has a cap on it) on the side of the Fuel Pressure Regulator on the driver side of the fuel bowl. You should see 65-70 PSI at idle. Anything less and you either need to replace the pump, or shim the FPR with the "BB mod".
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From: State College, PA
The fuel pressure at idle was between 50-60psi, usually close to 55psi. I unplugged the MAP sensor and when I stepped on the gas was easily able to get it up to 3000+ RPMs within a second or so. Before I had to flat foot it for a couple minutes just to see 2000 RPMs. It still wont idle right, but I'm assuming that's just because the air/fuel mixture is off with the sensor unplugged? Do you guys think its the MAP sensor then? Just wanted to check with the experts before I go buy one.