I have a 91 12v that I cant get shut off. When I turn the key It just keeps running. The only way I can get it to stop is by shutting the fuel off. Any suggestions?

 

5 will get you ten the little rubber plunger in the shut-off solinoid is torn.

 

Or the solenoid is stuck in the 'open' position.

 

I had that happen a few weeks ago. A chunk broke off the rubber plunger under the shut down solenoid. Fortunately I have another injection pump to rob parts off of. I hope you dont have to buy a complete solenoid just for the rubber. I read recently that Volkswagon pumps use the same solenoid and are much less expensive than buying one from Dodge or Cummins.
Good luck