I have a 1990 D150 318. My truck will putt and try to turn over, but never fully does. I'm settling towards a misfire issue. I've replaced the spark wires, spark plugs, and I'm going to be checking the distributor cap for damages as well. Other than that, any suggestions what might be happening?

 

have you double check to make sure you put all the wires in the right position? the firing order is stamped on the intake.

 

Yeah. I've checked the order 3 times. I checked the order from the book and online.

 

Turn over means the crankshaft will "turn" spin, crank when the starter is engaged. Sounds like your problem is it's not starting/running. Did you check for spark at the coil/plugs? Are you getting good fuel pressure, fuel pump priming /running? Did this problem start over night or was it an ongoing issue? Did you try giving it gas when cranking it over? Need more info.