hard starting 2003 Cummins Ram

[Super C]

One of our trucks at work has been giving us starting fits for the last several months. It is a 2003 Ram 3500 SRW with 5-speed transmission, 2WD, 4.10 gears. Everything is stock. The truck is in warranty, and has been back to the dealership numerous times, but is still not right. The problem is intermittent and usually occurs when the engine is cold. The engine cranks and cranks, but will not fire. No smoke, so it appears that it is not getting fuel. No codes. Sometimes it will finally start after much cranking, and sometimes it won't. We then haul it to the dealership, and of course, as soon as it arrives at the dealership, it starts. We have noticed that sometimes it will not idle right. We have also noticed that the "check gauges" light comes on intermittently, not very often, and not for very long. And sometimes, everything works fine! The crankshaft position sensor has been replaced. The injection pump has been replaced twice: the first time soon after we got the truck, because it was leaking, and the second time to try to solve this problem. Both times reman pumps were installed. The lift pump seems to be making good pressure. However, it appears that we are losing pressure between the injection pump and the injectors. The last time it was at the dealership, Chrysler instructed them to install some kind of pressure reducing valve. Now it starts hard all the time - sometimes it takes 2-3 seconds of cranking until it will fire, and sometimes 8-10 seconds. We have had a number of Cummins Rams in our fleet over the years, and overall we have had very good reliability, but this truck has been a real lemon and is souring the reputation of an otherwise great truck. Any advice would be appreciated.