1991 7.3 fuel problems
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1991 7.3 fuel problems
I have a 1991 F350 4X4. The fuel filter light came on and the truck died while going down the road. I removed the filter and it was half full. I thought the lift pump was bad so I installed a electric pump bypassing the mech pump. It ran good for the first 20 miles then the fuel filter warning lite came back on. As long as I stayed at 55 mph lite would go out. I have new lines going in both fuel tanks,no leaks anywhere, an a new fuel filter. The truck runs good as long as you stay at 55 or below.
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From: western SD
First off a couple of questions, Does it do this on both tanks, and what was the temperature at the time? It sounds like you have a restriction in your fuel delivery somewhere. Being the temps are starting to drop, fuel waxing can be an issue, but that happens more when the temps get closer to 0 degrees F. We have a farm tractor that does not likesummer blend fuel when the temps drop. the fuel will not jell, but the lift pump will collapse the rubber fuel lines with the thicker summer fuel when the temps drop.
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Yes it does it on both tanks, and both are full. I recently had the lines in both tanks replaced.I also keep an additave in the fuel. I was having a problem with it starting after sitting, it would start easy and run for a few seconds. It would start back up after cranking on it or bleeding it and then it would run fine until it set overnite. All lines were checked and found air bubbles coming out of injector pump. I thought it may be bypassing fuel back to tank after finding fuel filter low.
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From: Pomona, Ks
1991 7.3 fuel problems
I also have a 1991 7.3 with twin fuel tanks, it will start and die and I have to bleed it to get it to start and run! I replaced the return lines, o rings on injectors, fuel filter, and tried it on both tanks, full or almost empty, hot weather or cold, does the same thing! As long as you drive it during the day it keeps going. Once in a while it will miss when first started, catch up and run. Not getting fuel, just dont know exactly why. Im thinks injection or lift pump now!
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The electric fuel pump corrected my starting problems. I let it sit a week and it started up and ran fine. Just need to figure out why fuel filter running low on fuel. I think the fuel is bypassing and going back to the tank but dont know where check valves are at or how they work.
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From: western SD
Another question, where did you install the electric pump? Most pumps are designed to push the fuel. Most report that they install the pump next to the fuel tank selector valve in the drivers side frame rail just behind the cab. If you are using a pump that is designed to push the fuel, and you have it mounted in the engine compartment, this might be your problem. Do a fuel delivery test by removing the core from the schrader valve on the fuel filter head, and place a lenght of fuel hose over the valve andthe other end into a container. Energize the electric pump and let it run for 10 seconds. You should get at least 1/3 pint in this time. If you don't get this amount, either the pump is not the right one for the job, or you have a blockage in the fuel line befor the pump.
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From: Rockland Ontario
Whats the mileage on your truck?
Could be a "tank" problem. Start with the easiest one, on the side, I would say. Ensure your pick-up is clean and hasn't broken off etc.
Would be allot easier and cheaper than a pump, for now.
If there's a problem with that tank, correct it and only use that one to see if it clears your fuel problem, then move onto the next tank.
Thats what i'd do.
Could be a "tank" problem. Start with the easiest one, on the side, I would say. Ensure your pick-up is clean and hasn't broken off etc.
Would be allot easier and cheaper than a pump, for now.
If there's a problem with that tank, correct it and only use that one to see if it clears your fuel problem, then move onto the next tank.
Thats what i'd do.
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I did a flow test on the electric pump, it pumped 8oz in 10 sec. I understand that is enough to keep filter full. It looks like the fuel is bypassing the filter and going back to the tank when the truck is running. There is a rubber line coming out the top of the injector pump going back to the filter. A steel line comes out the bottom of the filter to the injector pump. I understand there is also a return line back to the tanks. Is there some kind of valve that regulates what goes to the filter or the tanks. If so where is it? Is it in the injector pump or the lines?
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