1994 Ram 1500 5.2L won't start when warm

[rmiller87109]

I have a '94 5.2L that starts fine when cold and runs great. However, when if I shut it down when it's warm, it will turn over but not start again until it cools all the way down. Any clues where to start?

[fredjacksonsan]

Couple things....if the fuel line is up against something hot, it could be vapor locking. Uncommon, but possible.

More common would be the Hall sensor in the ignition. These sometimes go bad. There's a thread in here where that is addressed.

[rmiller87109]

If it's vapor lock, would it need to cool down all the way (couple of hours) before it would start? The hall sensor might be a possiblility...would it run fine with a bad hall sensor? The pickup runs great once its started...no problem, no check engine light. It just turns over and won't fire until it's cool again once you shut it down.

[fredjacksonsan]

True enough; odd problem for sure. Vapor lock/fuel line would take awhile to ease off to where you could start it. Maybe there's a sensor that shows the wrong value if it's warm, keeping the computer from "doing the right thing" to start?

[rmiller87109]

Just for the sake of checking, I checked the spark. NO SPARK when trying to start when warm, but the spark is fine when running warm. Would the Crank Position Sensor do this?

[fredjacksonsan]

It could be; I'm not sure. But check this forum for references to the coil, sounds like something I read there.