this is a trouble shooting proceedure that I wrote for the navistar 466, your engine is a navistar 446 with perhaps a different software set , the mechanical checks are the same.
DTE 466 trouble shoot no start
I just finished a 466E , hard start/ no start chase.
It all seems crystal clear NOW.
Recap.
truck showed up operator said it wouldn't start without a shot of either,
engine cranked over fast, and it would fire up after it started to spin a bit faster on either.
I did all the usual checks , ECM power, Key power, (load tested and independent power source)
Once in a while the truck would fire up, adding to the confusion.
Check for fuel pressure at the filter outlet port while cranking ,I believe 35psi is minimum, I had 55-60.
I started the HUEI (this system uses boosted lube oil pressure to provide injection power instead of the cam shaft like you would see in a electronic unit injector system) specific testing by disconnecting the ICP sensor (injection pressure control).
this test lets the high pressure oil pump run wide open, so if the engine starts kill it immediately.
Engine start at unplugged IPC can indicate ICP or harness fault. (harness fault may be more common on later design engines due to the jumper harness in the valve cover.
IF still no start the next test would be to check for power and ground at the IPR, injection pressure regulator valve, it you have power and a ground, you can either buy a "break out" harness from Navistar or a Bosch injection dealer or you can slip a small spread out cotter pin in between the wires and the weather pack seal (be careful not to short things out and not wreck the seal or wire.
The jumper allows you to check voltage at key on, cranking and you can check the ground signal from the ecm by powering the multimeter from the starter relay hot side while key on and while cranking.
The breakout harness or a IPR pig tail will let you put 12V power and ground to the IPR. Again this if full pump, if the engine fires kill it.
An engine start with independent power to IPC points to probable ECM signal issues either in the harness or the ecm its self.
There is an oil temp sensor just above the HPOP (high pressure oil pump), un plug and loosen this sensor, oil should seep out of the threads, this is the oil reservoir for the HPOP. no oil here would lead to lube oil system checks, but that would be for a NO start scenario.
Next test is High pressure oil rail while cranking, for this you need a -6 jic run tee the tee goes into the high pressure line where it enters the oil rail on the head, a -6 jic cap is nice here so you can pop the cap on the rail fitting while you hook the tee up to the HPOP (high pressure oil pump) line.
You need a 4-5000 psi gage for the HPO rail test, check your rail pressure while cranking it needs to be around 875 I think to fire, I had about 700 ish most of the time,(I did find a o ring seep at the rail inlet, fixing this led to cold start after a fairly long crank.)
Probably at this time if you can either pull start the truck or either fire it you will find that you get at least 2-3000psi at throttle snap, if so the HPOP and regulator are probably fine.
Now if some idiot didn't order a truck with half the engine in the cab, pull the valve cover/ intake manifold (early engine) be careful of the injection harness pass through, it needs to be unclipped from the out side (make sure you mark the orientation).
have someone crank the engine, oil will probably flow from at least one of the injector bases.
pull said injector. Try not to laugh or cry at the obvious designed break down point.
the top oil o ring has a little metal backup ring,like a little piston compression ring complete with gap, a rubber or poly backup ring and an o ring, by this time the backup ring will have pushed into the gap and cut it's self, once this cut is big enough the o ring starts to cut, once it cuts you get hard start / no start.
Order 6 sets of injector o rings, the IH dealer was 5 x as expensive as the Bosch dealer. the bosh guy also sent a set of stainless compression seals to replace the copper ones in the o ring set.
Do all six injectors unless you really need to patch it and go, I found back up ring damage on all 5 of the others, and 1 was starting to have o ring failure.
there is a spiral retaining ring that is supposed to eliminate this problem.
spiral snap ring Hercules pt. no. WH-150 (from the net)
I couldn't find these in time, the guy needed his truck..
On my own engine I would try double rubber/poly backup rings or try to find a thicker backup ring to eliminate the gap ring. the second ring was a designed harder durometer one piece ring, the top ring could be made like this too.
This system is very similar to some 444E and ford /Navistar 7.3 systems.
