2003 ISX issue

When you turn the key you should hear a small electric pump running which Cummins feels they need on an ISX. Try waiting 20 seconds or so before you turn it over, could just be that you are losing your prime as you said.

 

I have the same problem in a 2003 Int. From my research I think my problem is the check valve that keeps the fuel from running backwards when I shut the engine off.
You can go to youtube and research this.
gonna change mine out next week.

 

I don't know about Cummins, but I had same symptoms in my Volvo D13, and was caused injector cups leak; I ignored this hard starting symptoms and drive, after few days the leak was worst, caused the cylinders to misfire, got stuck on the shoulder/ramp on I-55 in MO, and paid for towing to Volvo in Sikeston, MO. I would suggest to take it in shop, get a fuel system pressure check, before you waste $$$ like myself on towing.

 

Yes, check for the electric primer pump operation at key on. It should run for 2 minutes. Also, check for fuel leaking or seeping from around the electric pump. They do start to leak after time. The priming pump is on the suction side of the main fuel system, so if the priming pump is leaking externally when it is running, the fuel system can suck air from it when it is not.

 

Does your truck have a Davco 382 Fuel Processor?