Cummins 8.3 fuel problems

There is a small valve at the front top of the injector pump that is spring loaded and serves the function of creating back pressure to the fuel delivery system of the injector pump. Any unused, excess fuel is bypassed back to the fuel tank via this valve. If it fails, the result is loss of back pressure to the injector pump which will likely cause starting issues. If it was stuck shut, I could foresee the problem of excessive pressure in the fuel line from the transfer pump thru the secondary filter and up to the injector pump. The fuel line in this circuit is metal tubing not hose so the weak link could very well be the filter housing. I have not heard of this bypass valve sticking before, more the case of spring failing and loss of backpressure. This valve is cheap and relatively easy to replace if your handy.

A blockage in the fuel return line could also create the problem described but it's rubber and more likely to fail before spliting a fuel filter housing imho.