Tell you a little story... I bought a pump from our favorite surplus site; it was a cherry deal because the unit was brand speaking new. Even had the factory "unit shipped without oil" tag on it. Unfortunately, although it would start good and idle well, once you revved it up the engine would chug and blow black smoke. I couldn't figure out what was wrong so I gave it to a friend who was a diesel mechanic. After tinkering with it for a while he got the engine to run great. Thinking he had the problem solved, he put everything back together and it ran like crap again. WTF??? Digging into it further, he found a red storage plug had gotten sucked up inside the intake tube so the engine couldn't breathe. When he was testing the engine he had the air cleaner cover off so there was no restriction. He quckly knocked the plug out and the problem was solved.