sent injector pump away to be fixed, man said it was only hanging together but he fixed number one canister it was stuck,so i put pump back on tractor now number four injector is not working,i'm using tractor to feed silage on three cylinders a right pain. now could i take out the parts of number four canister with pump still on tractor, whats happening is with tractor running and side plate off injector pump the rod in middle of spring is not making contact with bottom piston what i tryed was sticking a screwdriver in between middle of spring with engine running and if i make contact with the rod and bottom piston tractor runs on all four cylinders.??? SO can any one help me, may be someone has a good second hand one.???????????????