Fuel problem
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Fuel problem
I'll try to be as brief as possible. I just bought a 1992 f-150 2wd, 4.9, single tank a few days ago. Truck is in great shape with only 67,000 miles. It has only been drive about 200 miles over the last 2 years due to the death of the owner. Yesterday I drove it to a town about 50 miles away, gas gauge was showing 1/4 tank and I was driving at highway speeds when all of the sudden it felt like it was out of gas (lost power and started bucking). I assumed my gauge was off and coasted into a station and filled it up but it only took 11 gallons (I think it's an 18 gallon tank).
I then drove home with no problem and then today I drove about 90 miles and again was at highway speeds with the gauge showing 1/2 tank and it did it again, lost power and started bucking. I stopped and never shut the engine off and it seemed to idle fine. I put a couple of gallons from a gas can in and drove to town, again at highway speed with no problem, filled it up, but this time it only took 8 gallons.
Anyone have any ideas on what is causing this? Any help would be greatly apreciated.
I then drove home with no problem and then today I drove about 90 miles and again was at highway speeds with the gauge showing 1/2 tank and it did it again, lost power and started bucking. I stopped and never shut the engine off and it seemed to idle fine. I put a couple of gallons from a gas can in and drove to town, again at highway speed with no problem, filled it up, but this time it only took 8 gallons.
Anyone have any ideas on what is causing this? Any help would be greatly apreciated.
Lead Driver
Joined: Apr 2001
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From: Midwest
have you done any tune up stuff to the truck? spark plugs,wires,distributor cap and rotor,fuel filter? start with the easy stuff 1st. any codes in the computer? I haven't had a ford truck this new,so I can't tell you how to get the codes,but the procedures are here in this forum or maybe the forum for your engine. just a few things for you to check before getting into the deeper,more expensive stuff.
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From: Louisville,Ky.
I would start with a fuel filter. I would also check the fuel pressure when this starts happening. It should have about 32psi at an idle and around 40psi under load or with the vacuum line removed from the regulator.
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Not disagreeing, but if it was a bad filter, pump, or tune up stuff, why would it all of the sudden start running normally as soon as I add gas? Is it possible that there is something restricting flow at the pump and when I add gas I flush it away from there for a while. Is there some type of filter in the pump?
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Could the gas cap really be it? I've had this happen on a lawn mower before but never a vehicle. This would explain why it starts running after I put fuel in. Do they really need to be vented. Is there any way to test the cap?
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I blewthrough the cap and compaired it to another one and it seemed OK. Couln't have gotten that lucky. I talked to a mechanic and he seems to think that there is a possibility that since the truck sat so long without driving that there may be rust or dirt in the tank that is clogging up the "sock" that lets gas into the fuel pump, and then when I put any gas in it washes enough away to alow it to run. Was hoping I wouln't have to take the gas tank off. Does this sound like it could be the problem?
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From: Louisville,Ky.
The tank doesn't vent thru the cap. It has a vent solenoid that goes to the charcoal canister. If it isn't opening like it should, you will create a vacuum in tha tank and it could cause starvation problems. That's why I suggested trying the gas cap thing.
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OK. I'm confused on how this whole vent. system works. According to what I can find in my Haynes, the vapors that accumulate in the tank when the engine isn't running go through a vent valve and to the charcoal cannister. Then when you start the engine they get sucked into the intake and are burned. If this is the case then wouldn't it create a vaccume in the tank without some other kind of vent? Does the vent valve on top of the tank also have an atmospheric vent in it? I can both blow and suck on the gas cap and air passes either way. I wouldn't think that the cap should allow air to go out of the tank, this would defeat the purpose of the cannister system as it would allow vapor to go into the atmosphere. I just want to make sure I dont have a vent problem before ripping into the pump and replacing it unneccessarily. Thanks.
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Problem fixed. I changed the fuel filter and everything is normal now. The filter was so full of dirt that I could barely blow through it. I still dont understand why it would run OK as soon as I added fuel to the tank, but I'm just glad I didn't have to pull the pump. Thanks for all the help. Just goes to show, start out with the simple stuff first I guess.