"Stop" Dash warning light

To answer tiffinboy, yes, my stop engine light would come when I pressed on the accelerator, and go off once I released it slightly (going up hill). It was a Saturday, and I got hold of Cummins emergency network, but they wanted $700+ two hours minimum labor to open their shop in Savannah on a Saturday. I was about 100 miles from there. Talking to them and to Spartan Chassis, and reading the Cummins book, I stopped and checked my water/fuel separator. First time ever, nothing would come out of the petcock at the bottom when I opened it. I changed it and that fixed the problem.