Fuel Systems Problems Desperate for help!
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Senior User
Joined: Jul 2003
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From: Virginia
Fuel Systems Problems Desperate for help!
I have a 1991 F250 2wd auto with a 302 V8. It will not start. I checked the fuel pressure on the valve and was only getting a little bit of a bubble with the switch on. It had this problem once before and we replaced the fuel filter and regulator and it still would not start. we got tired of messing with it and after a month or 2 went back and it started right up. fixed itself. now 3 years later i thought it was fixed but one morning it just wouldnt start. it was a little low on gas but i put some more in and that dosent seem to be the problem. my uncles 88 had a similar problem but it had no fuel pressure at all. this one has little. i wouldnt think it could be the pump as i can here it running. is their anywhere or way i can test the pump? also this model only has one high pressure pump there is no booster pump. thanks for any suggestions.
P.S. Carberator is lookin better all the time
P.S. Carberator is lookin better all the time
Senior User
Joined: Dec 2003
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From: Memphis, TN USA
If you could hear the the pump, it does not necessarily shows that it is performing as it should.
The fuel pump strainer might have broken to bits or clogged up. The fuel pump internal o-ring might be failing and allowing the fuel to escape back into the gas tank instead of pumping it to the engine.
Get a fuel pressure gauge and measure the pressure engine running and engine not running.
Never let the gas level close to empty mark as it sucks all around it and including the debris that is heavy and sitting at the bottom of the tank and that might clog the fuel pump.
The fuel pump strainer might have broken to bits or clogged up. The fuel pump internal o-ring might be failing and allowing the fuel to escape back into the gas tank instead of pumping it to the engine.
Get a fuel pressure gauge and measure the pressure engine running and engine not running.
Never let the gas level close to empty mark as it sucks all around it and including the debris that is heavy and sitting at the bottom of the tank and that might clog the fuel pump.
Cargo Master
Joined: Dec 2003
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From: Sunny Florida
I would say the pump or the regulator is bad. If the regulator is bad there will be gas in the vacuum line that connects to the regulator. To test the fuel pump it would be best done with a fuel gage. Bubbles in the gas does not sound good. Does gas squirt out of the needle valve if you hold it open and try to start the truck? It should have a steady stream. Be carefull because the dizzy is near by and spark and fuel do not mix well outside the engine. Just because you hear the pump doesn't mean you have volume and pressure.
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From: Virginia
the last time the truck had this problem i replaced the regulator so i dont think it is it because it didnt solve the problem then and it is the same problem now. as for pressure i did not try while starting but on the run posisiton it just barely bubbles out. i didnt mean to say there were bubbles in the fuel earlier. im guessing there is probably something wrong with the pump.also is it possible there could be a clog in the line somewhere between the pump and the fuel filter? last time the truck had this problem we changed the filter so it should still be in good shape.
Last edited by 1yamman350; Dec 23, 2003 at 05:43 PM.
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From: Virginia
no its a single tank truck. today i took the fuel filter off and messed with it a little and im getting about twice as much pressure as i was before. i still dont know i it was enough. then after cranking it a bunch in the past couple of days the battery started to get week so i am charging it tonight and see what i can do with it in the mornig. also if it wont start i am ging to get a pressur guage and see what readings i get. what numbers should i look 4?
New User
Joined: Dec 2003
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From: Michigan
I dont have my manuals near me or i would give you exact numbers but i would look for at least 35 to 40 psi also you have a fuel pump relay, ohm that out that could cause an intermitant problem. Also see if your pump is putting out the correct amperage through it.
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New User
Joined: Dec 2003
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From: Michigan
I dont have my manuals near me or i would give you exact numbers but i would look for at least 35 to 40 psi also you have a fuel pump relay, ohm that out that could cause an intermitant problem. Also see if your pump is putting out the correct amperage through it.
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From: Baltimore
Sounds like it got somewhat better when you messed with the filter. I suggest replacing the filter. Easy fix, could save you some time. When you get the filter off, dump it out on some sort of strainer and see if there is any debris in the strainer.
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From: Virginia
thanks for all the help guys. its going to be alittle while before i get to go to auto zone to get a gauge and filter but i was ust wondering how high the pressure shoots out of the shcrader valve when u press it down with somethin. i know this isnt the safest way to do it but its the only way i have until i get a gauge. my uncle says its should be shootin almost up to the hood when working properly. what do u guys think?
Cargo Master
Joined: Dec 2003
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From: Sunny Florida
IF I where doing these type of chack I would check for fuel pressure while trying to start the motor. Just keep the gas away from the dizzy and remove the coil wire.
I am not sure how far it should shoot but I would say the hood ge a good target. The main thing to look for is a steady stream while turning the motor over.
I am not sure how far it should shoot but I would say the hood ge a good target. The main thing to look for is a steady stream while turning the motor over.
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From: Virginia
i went to advance today and bought a fuel filter. the only gauge they had would have to have been ordered and they wanted 30 some dollars for it. im not goin to pay that much for a tool i use once. tommorow i will put on the new fuel filter and give it a try.