Fuel Line Return Check Valve issues

[Chris Wilkinson]

Been out for a while had my M923A2 1990 stored finally pulled her out changed out fuel filter and could not get the fuel pump primed. I had to have a mobile diesel Mech run by and it took us over an hour to get her primed then she started right up. He told I need a new Air dyer Yep new that but then he told me why i had issue priming the pump because my bajo bolt failed. He told me Cummins refers to it as a Fuel Return Line Check valve (has a little ball to check fuel return). When it fails the pump loses prime. Not a Diesel guy but working my way through getting her running. Any help with part numbers or part store that can help waiting on Cummins to respond

 

[LCA078]

Are you referring to the banjo bolt on the outside of the pump closest to the front of the engine with a line running down the side of the engine and back to the tank? If so that is an overflow valve to keep the fuel pressure in the PT pump at a constant pressure. Like you said, the little ball leaks from it beating up its sealing seat and/or the springs looses its tension. Either way, pump may bleed down losing prime. Best way to check is to use a pair of vice grips to close off the line below the overflow valve and try to start your truck. If it starts, that's probably your culprit. I learned that from the folks here.

As for replacement, there is a company called Tork Tek that sells adjustable pressure valves that are "better" than Cummins. https://www.torkteknology.com/adjustable-overflow-valves/. Maybe someone here has a better idea but I've heard on the board a bad overflow valve can have the hard start conditions you mention. But I also reckon when a truck sits for a long time, there is a good possibility air will get into your system and it can/will be hard to get rid of sometimes.