To check your vehicles ICP pressure, you can either use a (professional) diagnostic scan tool (not just a simple code reader) to monitor ICP_actual while cranking the vehicle.
BEWARE that most scan tools will show ICP actual as well as ICP desired pressure for the HPOil system. ICP actual is the ACTUAL pressure being reported from the ICP sensor back to the vehicle ECM. ICP desired, however, is merely the DESIRED pressure from the ECM. If ICP actual does not exceed (approx.) 450-500psi, then there is almost zero chance of the engine starting.
If you have a late 2004 engine, you can also check the ICP actual with a handheld voltmeter, by measuring the voltage at the ICP sensor (sticks up through the passenger side valve cover, just rearward of the GPCM (glow plug control module). Early 6.0L engines have this sensor located underneath the turbocharger, which make checking the voltage very difficult, if not impossible.
The ICP sensor, pictured here
will have a 3 wire harness that plugs into it. To check the voltage (ICP “pressure”), you will need to leave the harness plugged INTO the sensor, and probe the appropriate wire with your voltmeter lead (other lead to a ground point on engine, or neg. battery terminal).
Of the 3 wires, one wire is going to have a constant ~ 4-5.0vdc reading (with the key on, engine off), one wire will be ‘ground’ (check continuity to other grounds)...and the last wire (the one you want to check) will have a variable voltage which varies linearly with pressure.
1 volt is approximately equal to 750psi..so WHILE CRANKING the engine...if the voltage at that wire is not exceeding 0.6volts (+/- couple of tenths)...then the HPOil system is not producing enough pressure to mechanically fire the fuel injectors.
If the voltage is > 0.6v while cranking, then skip to page 4.
All this has determined is that the REASON for the no start...is RELATED to the HPOil system...however it has not been determined as to which component(s) have failed, creating the ‘leak’.

 

Ok i will check that when i get home. I have one other concern as well. On the sunday before i went for my trip, i swapped the box out for one that wasnt totally rotten. Is there anything on top of the tank i may have hit that could be causing my problem? Keep in mind that i drove the truck for a 3 hour drive on the tuesday as well as running around on monday.

 

If you did, you would either have fuel leaks or lots of bubbles in the fuel system. There's one line to feed the fuel pump on the frame (where the primary filter). The other line is return. And there is one plug there for the fuel gauge. That's it.

 

Yea no leaks to my knowledge. I dont know if the fuel system has bubbles or not tho

 

Ok, tested the icp. 3 wires going to it. Grey with red stripe, black with white stripe and blue with a green stripe.

G/R shows .8 with key on and jumps to .17 when cranking

B/W shows 5.0 volts with key on and goes to 5.1 while cranking.

B/G shows .3 with key on and .4 while cranking, my batteries are deadish now too.

 

So the B/G is your wire that sends oil pressure to the monitoring system. Weird that it's at .3 V with key on, but not the issues. But seeing it goes up to .4 Volts, is the right direction but not at all enough because it went up just 0.1V. It should go up to atleast to 1Volt at crank so 0.6-0.7 volts more from key on only. They say every 1 volt is 750psi, so you having just .1 volt increase means it's pressure is 75psi. So your issue is truly the high oil pressure system.
So from here on, my first suspect and for most people, is the IPr. To know if its operating properly, you ll need to bench test it (there's YouTube videos on that I think). but quite the job to get to if you don't have the proper tool, but its a few dozen bucks. If I remember you might be able to find it a at a princess auto. But even a auto part store may help with that. But if you don't want to bother with buying one, you ll need to pull off the turbo and few things more to get a wrench to it. It's in a awful place that damn thing.
So this is where your issues lies.

 

Im gonna charge the batteries up and see if the voltage goes up but i fear that youre probably right. If not the ipr then the next likely issue would be the stc bracket?

 

Yeah charge them and you still got nothing then definitely the IPr. But, you don't if the stc bracket hasn't been for the updated version? If so, it wouldn't be the problem. But another common problem on these things to can be the stand up pipe on the high pressure oil rails in the valve cover. They to have an updated version. They commonly leak too. But more so the stc if truly there is a leak.

 

Ive read a bit about the ipr bench test but im not fully confident in what ive read. Am i looking for it to close fully? 12v should close it fully and then what? If it closes the ipr is good? Doing it with the ipr still installed wont work because it wont be audible?

 

So the IPr, is normally closed, have 12 volt power to, it will open. So it should be click, but generally it's not to loud, so more of a feel of something moving, BUT there could be other problems, either that the screen is plugged, or the insides it clogged up, which stops the flow or jams the poppet inside. Some people try to clean it, but not so promising, but it's some where to start though.