I recently put a 2005 cummins motor in a 2004.5 truck.
I am running the 2004.5 ECU.
Truck would not start. It will start and run on starting fluid, but eventually dies out.

I seem to have good fuel presure at the rail, and thought injectors might be the problem.
I pulled different injectors and pump off of another 2004.5 truck that was running fine, and still no start.

The only code I am getting is PO633, skim key. Could this be the problem? I am running the ECU that match's the truck/ignition.

Not really sure where to go from here. I have read about lift pumps going bad, but I am pretty sure the only pumps I have are the pump in the tank and the injector pump?

Any direction would be appreciated.

 

To check your lift pump pressure you can pull the rubber hose off that comes from the fuel filter to the lift pump and get you a t plastic fitting and the same size hose and put it in the same spot you took the hose from. then the last connection on the t goes to a cheap fuel pressure guage from the parts house and it should run a max of 15 psi and no lower than 5 psi. make the hose to the guage long enough to reach out under the hood and under the windsheild wiper so you can monitor the guage after you get it running. Make sure all injector tubes are tight

 

swap the ecu, should make the troubles go away