I have a B 3.3 Cummings in a Doosan forklift starts fine when cold but will not start when engine is warm. Done compression test all cylinders tested ok. Any ideas, I'm getting fuel to all injectors while turning engine over.. Is it possible the injection pump is weak?
The 5.9 in my flatbed is starting to do the same thing. From what I've read, it's the injector pump diaphragm going out. It seems to be more of a problem with low sulfur diesel in engines not designed for it. A lot of the guys on the diesel forums are running 2 stroke oil as a fuel additive for that reason. I don't know how your forklift is set up, but I believe that when the lift pump starts to get weak it puts more strain on the injector pump and puts the kill on it early.