I've got a 2006 c7500 with the 7.8 isuzu engine that runs great as long as you spray it. If you try to start it without spray it wont catch. I have no pressure leaking from the lines to the filter. If I hook the outlet line up to the injection pump it leaks off to the tank with it not running. I unhooked the return line from the Injectors and the rail leaving it just hooked to the pump and with pressure from the tank it bleeds back to the tank.