Engine dies when it reaches operating temp
 

I have an '88 Cherokee Pioneer. I replaced the head gasket and drove it about 40 miles at highway speeds. Suddenly, the engine sputtered and died. When the engine had cooled off, I was able to restart it. However, it dies when it reaches operating temp. It will restart when it cools off again.

I replaced the ignition module with another one from the junkyard and it still does that same thing.

It doesn't seem like a spark issue, but rather seems fuel-related.

Help?