1985 300 SD Problem

Hi my name is Brian and I have a 1985 300 SD. For some reason the engine won't shut off when I turn the key off in the steering column, I have to pop the hood and hit the stop lever. Does anyone know why it won't shut off and how I can fix this problem? Thanks.

Most likely you have a bad shut-off valve. I have fixed them before because it's almost always a busted diaphram and I have a lot of those around, but more than likely you will have to buy one, but look for a vacum line that may have slipped off or that has broken down.(A vacum tester comes in handy here). I think the shut-off valves are around 50 dollars. The location is on the top and the side of the injection pump. Pretty easy to change as well.