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I have 1951 m37 cdn and a 1954 m152 cdn the 2 of them have the same problem. Starts great,idle great,drives great till you drive for 30min or more then it starts dying no more power like its running out of fuel. no change with choke on or off. when they stop running and you let them seat for 15-20min it fires right up with no question ask. one has 24v electric fuel pump the other has oem freshly rebuild. anyone have that problem?????

Is your gas cap vent open? If it is closed I think it can cause this problem.

Good thinking dap but in this case the 2 caps have the vent open

OK, it does sound sorta like a fuel problem, But.......I had a similar problem that was electrical. Truck ran fine until warmed up, then it would sputter, cough and quit, just like out of fuel. It was the filter capacitor on the input to the distributor. Either change out the distributor or if you have a good capacitor lying around, just change that. I you do not have either, as a temp or troubleshooting measure, just replace the filter cap with a piece of wire. That will tell you whether this is the problem, or it is something else. Took me a whole summer to troubleshoot this one out.

Are the vent lines still plumbed to your distributor with the correct fittings in the air intake elbow?

Bert

Coil??

Marc,

Someone had the same problem a month or so ago and posted to the tech section. I believe he found his coil to be bad. Seems there's a lot of bad coils out there these days.

regards,
bob

Sorry guys for the delay bin really busy. 1 truck has all new wiring and all new lines 2 of them distributor was rebuild and carb rebuild. I'm starting to thing if the heat riser is missing in they warming the intake to much and making the fuel boil. My m152 works fine in winter. Anyone have this valve rust out and have a problem like this???

Marc,

I would think your problem wouldn't be that hard to diagnose. Next time she quits after running 30 minutes or so pull a plug wire and check for spark. If good.....you have a fuel issue. By the time the fuel/air mixture gets to the heat riser in the manifold it's already atomized. More heat could make it vaporize.....but fuel vapor burns better than when it's simply atomized....so I don't think that's your problem. But that being said.....I've never had a heat riser stuck open. Maybe others can chime in.

regards,
bob

are the vent lines conected to the distibutor? just a thought.
hb

I had that same problem. It did end up being the gas cap. I did check the vent lines, and checked the coil
for correct ohm readings. Also check filters and valves in the fuel line.