Gunked up injector pump on NHC 250

[LCA078]

My M923 with NHC 250 has been sitting a while from a crank-no start issue and I've confirmed I have no fuel coming out of the fuel shut off valve when cranking. Here's what I've done so far:
-Verified adequate fuel flow to pump by pressuring fuel tank with 10psi so I don't think it's a fuel supply issue.
-Disconnected injector line out of top of the pump and verified no fuel when cranking.
-Removed manual fuel cut-off valve and verified no fuel coming out of fuel cut-off solenoid.
-Verified 24v to solenoid when start switch moved to Run.
-Removed solenoid valve and verified correct operation by blowing through it while Soldier B turned start switch to Run. I didn't hear a "click" like I thought I should when powered but it seemed to work fine with the old mouth-blow test.
-Paused here for a scientific discovery that when you're sitting on the left front tire, holding onto the engine with your left hand so you can get your head inside the engine bay to put your lips on a fuel cutoff solenoid that's removed from the IP but still connected to electrical system for the blow test and you give Soldier B the signal to move the start switch to Run, you are actually completing a 24v electrical circuit with your lips.
-Gave time for Soldier B to stop laughing hysterically when they figured out my shocking discovery.
-Verified no fuel coming up through IP port where solenoid mounts when cranking.
-All the time there was a very slight seepage of fuel coming out which I assume was from the pressurized inlet. But cranking didn't change the flow rate on this seep so I'm assuming something inside the pump is stuck closed.
-At this time, I ran out of daylight and called it quits.

The other thing I need to mention is this fuel system was/is filthy. When I bought the truck a number of years ago, the fuel smelled like varnish even though it started and ran fine. It was an auction truck so I have no idea what was run through it. When I changed out the fuel filter, the canister inside walls were caked in some brown tacky goo that easily washed off with a can of parts cleaner but it really made me wonder what was throughout the fuel lines, tank, IP, etc. Anyway, I started having a die-on-deceleration problem that turned into a hard start problem so it sat for a bit until now. I changed out the rubber lines but now it's a complete crank-no start with no smoke. When I pulled the manual and electric fuel cutoff valves off, I noticed a thin film of that brown goo again so I'm assuming the IP is just gunked up with same stuff. That goo washed off easily with Chemtool B12 but it really bothered me to see it in there.

So lots of rambling to know how I got here but here's the point of this thread: What's the best way to clean my IP? I plan to connect a garden sprayer to the inlet and pressurize with 1 gallon of diesel mixed with a heavy dose of injector cleaner, B12 and Seafoam witches brew and let it seep up through the IP and out of the top solenoid that's plumbed into a catch pail so none of it goes into my injector lines. Maybe this will help clean out something but is there anything else I can do? Move the accelerator lever back and forth and crank the engine for a bit? I don't know of any other movements I can do to help free up inside parts. Are there any ports I can use to better push the witches brew through to help free up the inner guts?

 

[WillWagner]

First thing is to remove the inlet fitting at the rear of the pump and use a mirror to look inside the hole. Have "soldier B" crank the engine and you watch the gear pump teeth turn. If they do turn, the gear pump is not broken.

On top of the pump is a large plug with a slot in it. There is a filter under that plug. It's purpose is to stop any metal that might occur when/if there is a malfunction inside the pump from getting into the injectors, however, if the fuel system is gunked up, that screen filter can plug. It can be cleaned if it is just goo in the system, but, if there is metal in it, it is next to impossible to clean due to a magnet being inside the filter. The flow through the filter is reverse from any other filter, it flows inside out instead of outside in.

If the pump is gooed up, you might be able to drain the pump anf then fill it with mineral spirits. There are two plugs, maybe 3, I am kinda forgetting these things, on the bottom of the pump body. You can remove the plugs, no parts will fall out, take the fuel shut off off so the pump vents, and drain the body. Re install the plugs and fill the body via the FSOV port or the screen filter hole, that is easier and does a better job at getting things down in all the little passages.

Let things sit for a day or so, drain it, put it back together and see what happens.

No bleeding necessary, the PT pump will suck a head of fuel 30 feet vertically. Just crank it, it will take a bit but if the pump is not messed up inside, it will lite.

I read you pressurized or put air in the tank, fuel did get to the pump inlet, correct?