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I have a '74 F-100 with a 1973 302 (not original) in it. The truck hasn't run for at least a year per the PO. I replaced the carb with a new Autoline and replaced the spark plugs. I have spark, I have fuel (although the gauge isn't working I dumped 2 gallons of fresh mid-grade in her) it started for about 30 seconds and then died.
This is what the new spark plugs looked like when I pulled the number 1 to check for spark. I did spray a little WD-40 into the cylinders and let it soak overnight before firing it.
I would strongly suspect a fuel problem.
Look down the throat of the carb and pump the throttle. There should be two strong streams of gas that shoot into the throat of the carb. If there isn't any then you have either have a clogged filter, bad fuel pump or the rubber lines in the fuel line between the tank and fuel pump are cracked and sucking air. There is also a filter sock on the tank's fuel pick up.
If there is fuel squirting out, then it's possible that the fuel is contaminated with water.
The first thing I would do is pour some good gas (not too much) down the throat of the carb and see if it'll fire. If it does, you'll know that's the problem. If it doesn't, then keep troubleshooting.
To answer your question. If that is the problem, drain the tank. You'll be time ahead by doing that. The fuel line driers work when you're talking condensation build up, but for actual contamination the only thing that works is draining the tank.
Okay Mike, what's the best way to drain the tank? Siphon it out?
What gas runs best in these old trucks? Premium here is 93, but I can also buy 110 at a station close by.
As for the gas, no need to run high octane at all, you're just throwing money away. Run regular unleaded, ethanol free if you can find it, but that's getting harder to find.
As for draining the tank, I've always dropped it. You won't be able to use a siphon hose down the filler. Most filler necks have a coil spring in them to stop a hose from being stuck down the filler.
If you have the time, you might look at using a piece of 3/8" hose and disconnect the fuel line at the tank and siphon it from that point. Depending on how much fuel is in the tank, it might take a while though.
Now would be a good time to replace the soft lines in the fuel system anyway.
Were you able to troubleshoot the non-running problem?
It does start and run for a few seconds with fuel down the carb.
I dropped the tank, and as usual you are right, the rubber hoses need replacing. Do you recommend a supplier for the fill hoses? DC, NPD, Auto parts store.......
Would now be a good time for him to cap the eec vent?
If you do block the vent, be sure to switch to a vented gas cap. If you don't, you'll have fuel supply problems that'll drive you even crazier, the worst case is a collapsed fuel tank.
Mike what do you recommend? Keeping the stock vent?
If the rest of the system is still there, I would keep it simply because it's there.
For it to be complete there should be a 5/16" steel line that runs along the inside of the passenger frame rail. That line should connect to a charcoal canister mounted in the engine compartment, on the frame rail, by the radiator. From there, there should be a ¾" tube that goes to the side of the air filter housing.
This is strictly an emission control device and doesn't really have any effect on engine performance.
If it's all there and connected, I'd keep it. If anything is missing or not hooked up, you could dump it, just switch gas caps.
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