This might be a shot in the dark but here goes, I gotta ‘81 250 with a 300 in it that’s got this weird idle problem.
I recently put a new Msd 6a box along with a blaster 2 coil in it. It runs great, but I’ll drive it for 45 or so minutes, get it at operating temp, and then I’ll park it and it’ll die after about a minute of idling. I’ll try and start it back up and it’ll fire and run for a couple seconds and then it dies and won’t start again until I let it sit and cool down.
It started doing this a couple weeks or so ago after I put a new head gasket on it and I thought it was the duraspark box that was the problem so I put the msd on it but that didn’t seem to fix it.
Any ideas?

 

Welcome to FTE

You would have been better off and cheaper to just replace the DSII box and if it did not fix the problem you then had a spare for when it dose go bad.

You need to do a little digging is it dyeing because of no gas or no spark is the question?
Still running the factory air filter, factory log exhaust manifold with the valve that put heat on the bottom of the intake manifold?
I would pull the air filter and get it to die and then check if the carb has gas in it or if spark has stopped as they are the only 2 things it could be.

My 81 F100 will want to die if I sit and idle for a long time when it is really hot like 95*+ and then try and drive off. I also let off the throttle and it recovers and I can then give more throttle and it is ok.
In my case I think the fuel in the carb is boiling when not moving the air under the hood when driving. This is also with the AC running full blast.
Once moving I do not have the problem even when I was pulling a 20' enclosed trailer but sitting at traffic lights was killing me.

BTW I am running EFI exhaust manifolds but run hot water to the heat the intake manifold and unlike the factory log manifold hot water is always heating the manifold.
The factory log the valve heats the intake till the motor get up to temp and then opens to let the exhaust out the pipe and not heat the intake.
This valve is known to get stuck heating the intake so may want to check this.

Report what you find or not and we can go from there
Dave ----

 

It did turn out to be the fuel pump that was causing the dying. What would be the best way to fix this issue, would buying a new fuel pump fix or is that just a temporary fix and it will start doing it again soon?

 

The easy and cheap way is to replace the fuel pump on the side of the motor.
Now with what new parts are like now days who knows how long it will last or it could be bad right out of the box.
Yes I did have a new fuel pump be bad out of the box. It was putting 18 PSI of pressure and going up when I shut the motor off, carb should only have 5 PSI max.

I would also replace all rubber fuel line at this time. it may look good on the outside but be bad on the inside.
Dave ----