Hello all. I am New to the forum but am hoping I might be able to get some help here. I have a 1977 f100 with a 300 standard transmission and original single barrel carb. The problem I am having is that the engine starts and runs great until it reaches operating temp. Then it just stops running. It doesn't hesitate or begin running rough. It just shuts down. I push in the clutch and turn the key and it restarts immediately and then runs for a few minutes before shutting down again. So far I have been through the entire fuel system replacing the fuel filter and pump as well as the rubber lines. I also dropped the tank and cleaned it out and reattached the suction screen. I also blew out all of the lines. This has not changed anything. The engine still shuts down once it reaches operating temp. Does anyone have any suggestions or has anyone experienced a similar issue. Any help would be greatly appreciated.

 

I forget the name of the part but whatever adjust the mixture after it warms up basically whatever turns the choke off is probably bad

 

Thanks for the idea. I will check that out.

 

Does that mean that a new carb is in order or can it be ordered separately?

 

I would check the ignition when it quits. Check for spark

I would suspect the box on the fender is overheating, and shutting down

 

or the coil is getting tired.
but usually when the coil is bad it will shut off when hot and not restart until the coil cools off.

 

It's been awhile since I dealt with them but I think it's a part on the manifold that uses vacuum to open and close that section of the carb .

 

i don't think it is the heat riser for the choke.
if that was bad it would stay engaged and the engine would not start hot.
it would also slowly die while running, while also blowing black smoke out the exhaust.

 

thanks to all responses. i have replaced the ignition control module and it is continuing to run after hot. i will see if it stays this way but for now all is good. my boy can't wait to take a ride. i bought this for him a year ago and we have been working on it here and there.

again thanks to all responses.

 

The 3 step scenario of a failing DuraSpark ignition module.

1) Module overheats, engine dies. Module cools down, engine restarts almost at once.

2) Module overheats, engine dies. Module cools down, engine restarts in an hour or so.

3) Sooner or later, usually sooner, the module overheats, burns out. Now the engine will not restart.

Taking the module to an auto parts store to be tested. Will test OK unless the little charmer has burned out.

Engine heat is the mortal enemy of these modules that are located on the left fender inner apron just in front of the firewall.

When replacing, use some washers to space it further away from the apron. The more airflow, the better.

DuraSpark ignition modules used in the 1970's were soooo unreliable, that Ford techs referred to DuraSpark as NeverSpark!

And btw: Inside the dizzy is the stator aka magnetic pickup coil (takes the p0lace of the points and condenser), it's another well known POS.

So if the truck begins to die again, this could be the reason.

 

Another way around it is to drill a hole for the wires in the fender liner, mount it on the outside and run the wires into the engine bay through the hole.

The unit is sealed, and outside air cools it better. It should last much longer "OUTDOORS"

Slop splashed by the tires should not matter


You run into that less with dedicated mud trucks - because the fenderwell skirts have been thrown away. That results in a lot more fresh air under the hood...