Truck hesitates to turn off

Do you think the engine is trying to diesel? Another thought, anything that gets voltage from ignition switch, make sure voltage cut-off is instantaneous.

When I turn the key off the truck bogs down the comes back up and then bogs down and finally shuts off

If no spark at the plugs, it is trying to diesel. Engine temperature too high--cylinder compression too high--hot spot in the cylinder. I am sure I am leaving something out.

I will check to see if there is still spark and get back to you.

Okay.

So I went out and tested to see if there was spark after I shut the key off and sure enough, there is. The guy I bought the truck from said that the computer needed to be reflashed because it came off of a different truck. Could the computer needing to be reflashed be causing it to have spark for a couple of seconds after I shut the key off?

No, it sounds like the alternator is back feeding the system because one of the diodes is leaking, to test for this remove the negative battery cable, then disconnect all wires to the alternator and make sure they are not touching ground, then reconnect the battery and start the engine and then shut it off to see if it shuts down,

Let us know what you find.

Best, Ken

I did the procedure that you have listed and I double checked if I did it right and I did and I still am getting spark for a couple of seconds after I shut it off

Hey Dennis,

It sounds like the auto shut down relay is sticking on, check the diagram and then try pulling the relay to see if the engine shuts down and let me know

When I pull the relay it won't start and I tried switching the relay out and it still doesn't help

But sometimes it shuts off when I turn the key off but it's very rarely

I see where Ken is going and I agree. The asd relay supplies voltage to several systems, including primary voltage to ignition coil. No primary voltage to ignition coil and no spark at the plugs, other systems will be affected as well, the vehicle won't start if you unplug that relay.
You need to check control side of relay, that coil looking line, voltage and ground. Voltage is fuse protected and hot all the time. The computer controls the ground for asd relay. Could be something wrong with ground circuit or computer. If computer issue, I don't know if a reflash might help?

Sorry for interrupting, just now saw the email notice?