1998 Monaco Dynasty 38'
45K miles
325 Cummins/Allison
While traveling I-55 in MS heading toward Memphis, I noticed a loss of power condition which seemed to come-and-go. Assuming fuel filter problems, I stopped in a rest area and after a diesel bath, I was back on the road. The intermittent problem continued. When we pulled in to a campground for the night, the engine would not cut off (I had previously noticed a short, 1-second delay when switching the key off but thought it was my imagination). Turned out that the fuel shutoff solenoid bracket had broken and the solenoid had finally dislodged. It was hanging by the wiring and had shorted internally. We had to raise the bed to stop the engine for the rest of the trip and went through four more of the $397 solenoids before I traced the problem to a relay whose contacts were sticking closed. (BTW: A "certified" Cummins repair facility did the replacements and a mechanically-challenged owner was finally fed up enough to solve the real problem.)
My advise is to know where your shutoff is located on whatever diesel engine you have. I can testify that a cardboard box over the air intake on a turbo charged Cummins is NOT the way to shut the engine down. :-)