2005 Hatz 2G40 No Oil Pressure

Ok, it's definitely not a class 7-8 truck but I'm desperate for some help!

I bought this little Hatz 2G40 about a year ago, finally got some time to play with it. It was allegedly military surplus, was the APU from an M1 Abrams tank. It had very low hours, looked very clean, sealed up and stored properly. Finally got a starter and a crank pulley that kind of fits, so I tried firing it up, but it won't fire correctly. What I've determined so far, everything seems to be in good order except it doesn't build any oil pressure. The oil pump brings oil up to the head, it drains back down through 2 metal tubes into a banjo fitting where it can fall back into the crankcase, or splits off to the injector pump. I loosened the banjo fittings on the cylinder head, crank the engine, but no oil comes out. I tried bleeding air out of the injectors, they are getting fuel but not at high enough pressure. The fuel is gravity fed from the tank, the lifting pump brings it to the injector pump, but without adequate oil pressure it can't generate high pressure fuel.

I inspected the oil pump, everything looks normal there. I drained the oil and dropped the pan, checked the oil pump feed tube, the mesh filter, blew shop air through it to make sure it's not clogged. I put a hose on the feed tube with a funnel, filled it with oil, turned the engine by hand, it pumped oil until it started dripping from somewhere up inside the engine, but still not going to the head!

I pulled every fitting, cleaned and checked for blockage, still no dice. A friend mentioned that sometimes engines can have an oil diverter valve or something like that, but I can't find anything like that. There's not much info on these engines which is odd because the company is still in business and these engines seem fairly common. There's a user's manual but it doesn't give much information. I checked the oil filter as well.

A couple things worth noting, this engine was allegedly modified to increase power for it's application in the tank. Looking at the users manual, I see a couple things missing from my engine, and some extras that I'm not seeing on the stock ones. Most notable, it appears that my engine has a larger oil pan with heat fins for cooling, it also has 4 drain plugs (not joking) in addition to the stock drain plug that sits higher up (where the oil pan bottom used to be, about 2" shorter) I can see the cut out where the oil feed tube used to sit in the stock engine, and in mine it comes down further.

There's a few options mine was missing, like the oil bath air filter, but those are the main differences I can see. Does anybody have any experience with small air-cooled diesels? The engine is stupidly simple, so I guess I'm stupid for not figuring it out yet lol. I'm not a diesel mechanic, I own a shop working on hybrid electric vehicles, but diesel has always fascinated me. I got this engine to do some experiments with water-diesel emulsion and ozone enhanced combustion, combined together. Why? Efficiency and emissions. How about a diesel that burns so clean it doesn't need a DPF or DEF, that would be pretty nice right? I wanted a small air-cooled CI engine for these experiments, this engine is perfect, if I could just get the dang thing running! There's a high chance I'll blow it up pretty quickly lol. I see these engines on Ebay for $5k, I paid $500 so I thought I did pretty good (that same engine for $5k has been up for sale for over a year, so...)

I'll try to get some pictures loaded up. I know it's a long shot, but I appreciate any help! Thank you!

 

PS: In the last picture there where I'm pulling out that solenoid pin thing with a pick tool, I have no idea what that is or what it does, nothing in the manual about it, has 2 o-rings, it's like a brass piston thing, seems like it has 2 positions. I tried cranking with it pushed in and pulled out, no difference.

I set the oil lines back in place for the pictures. I also have a fuel line disconnected.

 

That makes sense what you're saying, I'll give it a shot! I did try cranking it with it pulled out some but not for that long, so I'll try it again with it pulled out.

It's actually a 2 cylinder engine, I really want to hear it run! I got a 3 cylinder Kabota lined up if this one doesn't work out. At least with the Kabota, there's tons of information

 

Just an update, I tried messing with that oil pressure relief valve but it didn't make any difference. The engine probably needs to be disassembled, there's got to be something stuck in there that's blocking the flow. I will try contacting them. On another note, a friend of mine owns a junkyard, he's had these 2 Kubota RTV900 Utility Terrain Vehicles with a liquid cooled 3 cylinder diesel. They've just been sitting and deteriorating so we worked out a deal. One runs and drives but guess what issue it's having? Low oil pressure! Thankfully there's much more information on them and there's several things I need to check. Apparently there's an aluminum plug that falls out of the camshaft and then oil leaks internally. So I'm gonna drop the pan, see if I can find the plug or metal debris and go from there. This Kubota may offer some clues on my Hatz!