Nasty Fuel
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Freshman User
Joined: May 2005
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Nasty Fuel
I have been experiencing a fuel problem with my 1968 F-100 302. About a month ago I replaced the fuel tank because the old one was full of rust. The new one (from a local junk yard) looked almost completely rust free.
It seems that the truck will run fine until it gets warm. If I shut off the truck once it is warm, it will not restart. It just wants to spit fuel back out of the carb and backfire. It does not do this until it is warm and I shut it off and try to restart it. After this happens, the canister type fuel filter is full of brownish gas (not flakes, just off-colored gas).
If I empty the fuel filter canister, refill it with good gas, and put it back on, the truck will run fine.
My question is why the 'rust' in the fuel doesnt seem to cause a problem until the truck is warm?
Why is the truck sputtering and backfiring only when it is warm?
Is there an easy way to look at the fuel filter element and tell that it is clogged or needing replaced? Like I said, there arent any rust chips, just ugly looking gasoline, so the filter doesnt really look clogged.
I'm wondering if the bad stuff in the fuel is fine enough that is is slipping through the filter, but it seems like there should still be enough fuel to burn and the truck might just run rough or have strange exhaust odors...
Any Suggestions?
It seems that the truck will run fine until it gets warm. If I shut off the truck once it is warm, it will not restart. It just wants to spit fuel back out of the carb and backfire. It does not do this until it is warm and I shut it off and try to restart it. After this happens, the canister type fuel filter is full of brownish gas (not flakes, just off-colored gas).
If I empty the fuel filter canister, refill it with good gas, and put it back on, the truck will run fine.
My question is why the 'rust' in the fuel doesnt seem to cause a problem until the truck is warm?
Why is the truck sputtering and backfiring only when it is warm?
Is there an easy way to look at the fuel filter element and tell that it is clogged or needing replaced? Like I said, there arent any rust chips, just ugly looking gasoline, so the filter doesnt really look clogged.
I'm wondering if the bad stuff in the fuel is fine enough that is is slipping through the filter, but it seems like there should still be enough fuel to burn and the truck might just run rough or have strange exhaust odors...
Any Suggestions?
Elder User
Joined: Dec 2001
Posts: 800
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From: Ontario, canada
Originally Posted by 1968F100ShortBed
Can you be anymore specific, or describe the cause of my problem? I rebuild the carb just one month ago...
Sounds to me like a vapour-lock problem. Did you run new fuel lines?
did the old ones get routed closer to a heat source?. Did you use the stock spacers and gaskets between the carb and manifold?
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Freshman User
Joined: May 2005
Posts: 38
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I ended up running a rubber line from the pump on the block up to the carb. The hottest thing the line touches is the valve cover. I used the stock spacer and a new carb gasket when I rebuilt it. And no, I never had the carb off at the same time as the tank.
Any ideas why it starts backfiring and sputtering gas only when it is warm? It sounds like a timing issue, but why would timing become a problem only once it is warm?
Any ideas why it starts backfiring and sputtering gas only when it is warm? It sounds like a timing issue, but why would timing become a problem only once it is warm?
