i have a 1992 mighty max bought it a week ago and it was sitting for 4 years the guy I bought it from said that he thought the head needed to be rebuit, I took the head off that was just on it and the original was in the back I cleaned it up and put it on. it started up but it has a bad miss and idles roughly. I just put new plugs in and they are already black, when I have the battery hooked up the fuel pump doesn't stop running, im wondering if it would be because the relay switch is stuck or the cut off is. I pulled the fuel line that goes into the fuel rail off and held it as hard as possible and pressure just kept building up and the fuel pump didn't shut off.