The Stovebolt Site Forums The Shop Area Engine Shop Engine stalling when hot

Recently I loaned my new truck out to my daughter. So for the last 3 weeks I have been driving my 49 3600. As long as the temperature outside stays below 70 degrees I have no Problem. On the warmer days after driving 15 miles on highway I can come to a stop light and idle waiting on traffic and when the light changes take off. The truck will die on acceleration like running out of fuel. I can let off throttle and runs fine. If I accelerate slowly it will straighten out. On the cooler days no problem. At first I thought maybe vapor lock but one day it was only 70 degrees outside. Any Thoughts? I tried filling up with non ethanol gas. No difference. Engine runs cool and has to be running a little rich will start outside 33 degree morning with out choking. Runs great going down road. No hesitation on acceleration under normal driving.

Don't rule out ignition problems but check fuel pressure at carburetor and output volume of fuel pump. Fuel pressure should be 2-4psi. Mine is 2.5psi. Then move on to the carburetor.

When the engine is stopped, look down the throat of the carburetor and manually goose the throttle. Do you see spurts of fuel when you do so? Do this when the engine is hot as it would be when it's causing problems. If you don't see squirts of fuel, your accelerator pump is bad.

If fuel is leaking from the carb into the intake, you may be flooding out. When engine is hot and turned off, Look down the throat with throttle open and see if there is fuel pooled on the intake runner.

What kind of fuel pump are you using? If it's a new mechanical pump, that could be your problem. They are all absolute garbage. Find a 30+ year old USA made original style pump and have it rebuilt.

I've had 2 incidents in the last couple years involving the AD truck and my Cadillac similar to your problem. In both cases friends were saying vapor lock! vapor lock!

In the case of the AD truck, it turned out to be the brand new Chinese fuel pump that began to fail gradually - when hot - and finally ceased working altogether. A second, brand new pump wouldn't work at all. Rebuilt the original glass bowl pump and all has been fine for a couple thousand miles. The picture is the one that wouldn't work at all.

In the case of the Cadillac, it turned out to be a partial/intermittent blockage in the fuel outlet in the tank. Car would run fine until "hot" and then conk out and not restart. Whatever was causing the blockage would move around or settle after a ride on a flatbed and the car would immediately restart and operate normally until the mystery item blocked the outlet again.

The fuel pump looks similar to the one in the picture. No where near that nice looking but doesn't have fuel bowl on it. It has the original style carter carb on it. It has a new pertronix distributor and coil. new wires and plugs. I was leaning toward fuel pump. Have to drive it until i get my other truck back. Maybe it will quit on me and I will find it then. The truck amazes me more everyday. 75 years old and still drives and handles well. And to think i was scared of all the folks talking junk about the old babbit pounder. Thinking a rod would sling out the side if I drove it any. I have put 2500 miles on it since I drug it home.

WOW! I just submitted a post about the exact same problem. After two new pumps didn't fix it I added an electric inline fuel pump between the tank and mechanical pump as somebody suggested. That "fixed" it but not really, I wasn't buying it but maybe, like Otto experienced, both of my new fuel pumps were bad after all. I am now running a big block and wish I had measured the pressure going into the carb like Otto suggested.

That pump in the picture is brand new and doesn't work at all. I posted it to show you that looks are deceiving. Here is the type of pump you want to find. Buy one and have it rebuilt by Then and Now Automotive www.then-now.com

Someone on this forum said they bought a glass bowl type pump from Jim Carter. I don't know if those are rebuilt originals or if they're new. I don't trust any of this new stuff anymore.

Test your fuel pressure at the carb.

Yes, these trucks are tough. I use mine a s a regular vehicle. I've put over 6000 miles on it in the last couple years.

Thanks again Otto! My post is now up under "is it really the gas?". Quite a coincidence!

I have an old 1940 special deluxe at the house was going to fix but now use for parts. I will look at it tonight and see which pump is on it. If it has the glass bowl type I will pull it and rebuild it myself and see what it does. If the car runs the same pump? Thank you.

There's a common theme here- - - -and it isn't fuel related.
Jerry

Well if it quits on me I will let you know what it is. I have old distributor under seat with new points when ever that one gives out. But for now I think it is fuel.

Excellent plan to have that extra distributor on board, regardless of what is currently causing you problems.