The starter cranks but the engine is slow to start. (My definition of grinding.)
The fuel pump has been replaced in the last year. The current starter is a rebuilt one less than two years old. Only one fuel pump in the system.
When it cools down, it is easier to start.
OK.. Just trying to make sure we're speaking from the same vocabulary list. What is slow, the cranking, or does it crank at what seems the normal speed but just doesn't start?
Is this fuel injection or a good ol' carburetor?
Reason for question - if carb, it could have a sticking float or similar issue that allows gas to continue to drip into the intake while it sits when warm. Then when you come back to start it, it is flooded for all practical purposes, and has to crank (and crank) until the raw gas clears out. If this is the case, if you put the gas pedal to the floor (thus opening up orifice for more air) it should clear out the extra gas and allow it to start. Just be ready to get the lead foot off the gas when it starts.. ;-)
The other scenario with a carb is a vapor lock. That probably needs to cool down to remedy. They do make thermo-insulating gasket type things to put between carb and manifold to help cut down on heat transfered to the carb.
If it is fuel injected it could be a similar condition (flooding) due to a dripping injector. Throttle-body injection - which acts almost like a carb - especially in Chrysler products of a certain vintage would do that. (I forget what years but I had a company issued vehicle that did that.)
We’re way out of my league here, but I’m assuming this is not a computer controlled truck and not fuel injected. Could there be a choke issue? Chokes fine when cold but floods the engine when warm?