Cummins ntc 350 miss

Your tank vents should be venting off the pressure, check them and make sure they are clean and functioning, the fuel tanks are not designed to be pressure vessels, also keep in mind that diesel ignites by pressure. One reason I advise to set pump to manual first is to eliminate randomly buying and replacing parts like the solenoid, the reason I would try this is because I have seen battery cables that had chafed and would randomly short out and cause intermittent power loss to the solenoid, also wiring issues causing the same thing, as well as the solenoid just wearing out. By setting it to manual it is a test that costs you nothing as well as eliminating the electrical possibility.