I'm new to the forum. I have a 1987 dodge w150 power ram with a 318 and 2 barrel. I've rebuilt the top end of the motor and and cleaned the carburetor, new radiator water pump and timing set as well as a full tune up, but just recently it has started sputtering after I turn it off like its still getting spark and fuel in a couple cylinders, I know I have a problem with the key ignition its very touchy and has to be in just the right place for the heat and fan to blow. the compression is good, there's no air leaks I don't know why its acting like that. This is my second dodge ram project I'm pretty mechanical but this has me needing a second opinion, Is it the key ignition or something else?

 

timing issue it sound like to me

 

This problem is better known as dieseling or run on. It is some times a timing problem but it could be the idle is too high, carbon build up in the cylinders, or excessive engine temp at shut off.

You mention the switch problem. You can eliminate the electrical system as a possibility when it is doing this by pulling the coil wire to shut it off. I would recommend using something non conductive if you try this. If the dieseling is still there it is not the electrical system.

 

I have had the same problem with my 86 /6. It seems there is just a little extra fuel that causes this I never occurred to me that it would need spark as well to cause the dieseling. Maybe the timing is too advanced.

 

It doesn't necessarily need spark to cause dieseling/run on but a bad switch was the original question so I gave him a way to test that.

 

it must be electrical, I let it warm up (it only does it when warmed up) turned it off by the key and it did the same thing, then I started it back up and disconnected the coil and no dieseling did it twice to be sure, its something in the ignition switch I believe, timing is right on, checked it with timing light, Also I'm wondering if it could be vacuum related? Vacuum Advance possibly?

 

Just so you know, almost all dieseling problems happen when the engine is warm. I would find it hard to believe that a vacuum advance would run OK and malfunction only at shut off. If you believe it is electrical and you know you are having switch problems I would suggest you fix the known switch problem and see if it fixes the run-on problem.