The little bolt is the fuel return line. You have to loosen the mut on the big line on top and crank it to see if it is getting fuel to the injectors. One other thing that has been a problem on ours is the fuel shut off solenoid. It is on the top back of the IP and is slightly difficult to get at. I had to pull ours out in a rainstorm one time. If you take it out and pull the plunger inside out and then reinstall it without the plunger that might get it going again. It might also have air in the injector lines and loosening and cranking should bleed them. If you have to pull the plunger out of the fuel valve there is a lever on the side of the IP to manually shut it down.