48 Willys - Weirdest Engine Problem Ever

So, i have a 48 willys pickup, go devil,

problem. truck idles and starts great! i mean perfectly. truck also runs even better when i start this thing in 5 degree weather it idles happily and will idle till the ends of the earth. problem is that whenever i drive the thing, about 4 miles from the house, it starts to buck, and cough, and choke, and die. i let off the gas, she idles perfectly. then if i try to get it to idle up, it will the first time i try it, but as soon as i go to give it clutch, she dies right out and comes back to idle. then if i try and idle it up again, she WILL NOT do it, it will choke itself, and pop and fart and buck, then return to idle. once it stalls (which it will after a while) the starting is very difficult, and often kills the battery.

ive never seen an engine run great in cold weather, and get worse as it warms up. she died today plowing my cousins driveway, which it had only been doing in low range. i barely was able to get out of the street by letting it idle, and barely letting off the clutch to get it going on idle/

we're getting 8 inches over the night, and she's pregnant.

anyone know whats going on.

if i went out to it right now, and started it up, it would idle great, drive perfectly fine, and have all the power in the world for like 5 minutes or so. then the problem arises.

 

Had a problem similar to yours on my v8 conversion. Heres what I did, I would drive it till it died or sounded like it would die, then I sprayed I little starting fluid with someone on the throttle. When I hosed it would not die, this let me know it was a fuel problem. turns out my float was too low. It took a while for it to finally drain the bowl that is why it seemed like it was getting hot and would run forever at idle. Try the starter fluid trick to see if it a fuel problem. Good luck.

 

X2 on the float level

 

sister thread: http://www.jeepforum.com/forum/f8/48-willys-weirdest-engine-problem-ive-ever-known-1159175/

 

If it's an L-head, do you have a glass bowl fuel pump?

If so can you see the fuel level?

 

no, just a capped fuel pump. but it has a clear glass filter just before it, and its full with fuel.

 

If you've done all the tune up things, check the distributor shaft for run out. I'm dealing with a similar problem, turned out to be a worn distributor. It flopped around enough off idle so the points weren't opening the proper amount. New distributor shaft bearings, and runs great now at any RPM.

 

I am going to say you are having carb icing issues. With the current weather conditions you mention it sounds like classic carb icing. If you shut it off and let the engine heat get back to the engine compartment does it run fine again for a few minutes. You need to be picking up heated air into the carb from around the exhaust manifold. I am not familiar with what a stock flatty L head intake is like but I would think there is a way to pull heated air into the carb. This is why most aircleaners from 60s and 70s cars have a heated thermal valve on the snorkel of the air cleaner to pull heated air in when it is cold out. Hope the info helps you out. Good luck.
Greg

 

Had a very similar issue, everything checked out great- float level, fuel pump, distributor etc... drove me nuts.

Finally checked the fuel lines and found a small crack in a rubber portion near the tank which let air in vs fuel. At idle, it would not have any affect, under higher rpm's it would create enough suction that it would suck in air versus fuel creating fuel starvation. When I let off the gas and let it idle for a short period it would fill the fuel bowl back up resulting in a great running engine.