1998.5 dodge diesel 24 valve new lift pump won't start if the engine and weather is hot running temp will turn over but wont start

this is a hard one without seeing it haha. my guess just a possibility is maybe fuel getting a vapor lock before it actually gets to the motor. have to checked to see if you get fuel at the injectors. (line going into valve cover) crack one and see if your getting fuel when you crank it. may possibly have a weak injection pump? try that and get back with us and hopefully someone else can throw some other ideas out there to you also.

Your bleeding down fuel pressure some where, prolly from the return side of the pump. fuel goes in, circulates around the pump internals, then gets fed to the delivery lines and injectors, some also goes out the return and back to the tank. on these Vp44 pump trucks its very likely that your leaking from the return side of the pump. The VP44 fuel system isnt a self bleeder like a common rail, due to the fact that fuel pressure drives your injectors not a electronic solenoid.

I bevieve there is a tsb to add a fuel pump into the tank

Use injector block off lone caps it's one of your imjrctors