ISX running on one bank

[manolumber]

Thanks for the quick replies guys, much appreciated.
Checking grounds is always a good suggestion. I`m assuming the rear bank grounds at the same location as the front bank? If that is the case, the rear bank is functioning properly so ground must be good, right?
Havnt checked fuel pressure but I would think the ECM would set a code if low enough to starve one bank? If the fuel pressure was low wouldnt that affect both banks? I will check today as that was one of the checks I planned to do. Operating pressure should be about 250 psi, correct?
Wholesale changing of parts is not something I ever do. Initially I swapped the front and rear actuators and the issue stayed in the front bank. I also did an injector check valve test, both via Insite and manually, on the front bank and all checked OK. But there is alot going on in those injectors so in spite of not picking something up visually on inspection it was decided to go ahead and replace them. The downtime for this employer is as important as the cost of replacement parts, a little different mindset than an owner/operator. I am more conservative re the cost and I pride myself in being a good mechanic but the bottom line is the employer is paying me and he owns the truck. I will hold on to the parts and use them for future troubleshooting/repair as we have quite a few of these ISX`s so the money will eventually be recovered.
If I use a DVOM at the fuel actuator connector on a good known engine the DVOM shows a steady 5 to 6 volts while running. I assume the ECM is firing the actuator so quickly it translates into what appears to be a constant reading. When I do the same check on the problem vehicle I get the same readings.
I`m very suspect of the wiring to the front fuel actuator as the ECM displays a code for same every once in a while. Perhaps the wiring is hanging on by a strand or two resulting in good continuity tests but cannot carry the current necessary to cycle the actuator? I`m considering bypassing the circuit with an overlay harness, only 2 wires from ECM to actuator.
By checking combustion gas in the fuel system I`m assuming you mean thru the injectors or cups? I did a "bubble test" at the actuator and there was no indication of air in the fuel circuit. Any idea how I could isolate the head/fuel block to check for a crack or obstruction?
Thanks again for the help and suggestions. This one has me chasing my tail!