NHC250 sitting over 20years...how to go about starting?

so I have an NHC250 which came with paperwork indicating is was rebuilt by the Army in 1995 but been not run since. My question is what steps beyond the obvious are required to bring such a long dormant engine back to life? I have pulled covers and inspected the valve train...all looks good but very dry in there.

The obvious is to pull injectors, get some penetrating oil into cylinders, bar over engine by hand,
but not so obvious is how does one prelube the block, what to do with the dry fuel pump, should injectors be bench checked first? I am assuming everything is bone dry and there is no oil anywhere other than in the pan.

what is your experience starting these long dead engines and what are the potential mistakes a person can make?

Remove the oil pan to inspect the bottom end and pour some oil on the crankshaft. Best time to replace the oil pan gasket and rear main seal if it looks questionable.

prefill the oil filters, remove the valve covers and fill your engine oil from the top working your way across all of the head, letting oil work it's way down through the motor. Use some assembly oil, has a zinc additive in it that helps reduce wear/tear.

Prime and bleed the fuel system, running a higher concentration of fuel additive (power service, diesel kleen, ....). Fire it up.

This is assuming that the engine has been sitting sealed in a container.

many thanks for the reply

any way to pressurize the oil galleries and circ L/O through the block before cranking it?

also, the engine has been in its container for the 20 years but the seal was broken at some point in the past so there is the potential that condensation occurred inside the block however the intake and exhaust ports had covers on them

btw, here's a pic of the engine as she sits today...the gray paint is two part epoxy primer

I don't know a lot about the 250, but if you can pull the injectors, I'd just spin the motor with the starter. Since there is no compression, there is little worry about messing up the bearings.

To circulate the oil before firing up the truck you could disconnect the fuel outlet line from the injection pump and crank the motor over with the starter a few times. 5-10 second cranks, 3-5 times. That way the engine gets lubed at lower rpm's, and the injection pump has fuel flowing through to lubricate it as well.

The fuel coming out of the injection pump will be higher pressure, so either plumb it into a return line to a fuel tank, or let it make a mess.

If you had some sort of pump you could open the oil gallery and hook in your pump and psi the system up with fresh oil. That would get oil to all the parts that need it. You can bar the engine over while the pump has the psi up. I wouldn't run the pump to long of a time though. You can do the same thing to your fuel system. If you do this on the fuel sys I would use a lot of Howes fuel treatment it has more lubricant than just diesel.

There is a process for this in the tm's. Sorry cant remember which one. When I went through this I made an engine oil primer out of an air tank. About 1.5 gallons of oil pressurized with air at 45 psi. Open the valve, and crank her over. This takes the place of the priming pump described in the tm. Good luck!

I would not take anything apart like injectors or pan. Yes on the priming the oil system by way of any oil port galley. You could fill the oil canister if you just loosen the canister and rotate the can till the oil drain is up and inject oil there. I would like said not supply fuel and the way she sits now there is no fuel lines hooked up but you can hook up starter and spin over. If you were worried about dry cylinders you could spray fogging oil after you prime up the oil system right into the intake while cranking. If you could find some kind of 12 volt pump that would move a light weight oil you could prime up the system or build a pressure pot that you fill with oil charge and air it up and inject the oil into the oil canister drain port. Just make check to make sure there is an oil filter in the canister. The pressure pot could be a new portable air tank filled with oil and just fill with oil put 30 psi air and flip it with exit port down to inject oil into the oil filter canister.

My local diesel mechanic said most likely you will won't get oil pressure from spinning the engine over. He recommended disconnecting the lines to and from the oil pump and use an alternate pump to prime the system. Check to see if the engine is free by barring it over using the accessory drive. If it is free, I would recommend removing the injectors to get some kind of lube is the cylinders. Remember that any kind of fuel or oil in the cylinders with enough compression will ignite.

Thought that is the idea to get primed with oil and fired up. Can be done just where it sits. Myself I would have the fuel system primed and ready to go with a remote tank. I would use the remote oil pressure system and watch a attached oil pressure gage. When the oil pressure comes up fire it up. Just a garden hose attached to water pump intake.

I would not take anything apart either. Fill the oil to correct level, add 2 batteries and fuel supply, and crank it while spraying some aerosol lube into the intake. Engine will build oil pressure while cranking, though it will take say 10 seconds or so of doing so. Not much load on bearings until the engine is under load itself and the pistons are pushing down hard on the crank from combustion. Even at an idle, they are only pushing hard enough to keep the engine running. Just cranking without ignition is not much load on anything at all, even under compression.

Forcing oil into an oil port such as the oil pressure sending unit hole is also a good idea if you want. Not such an easy task though unless you make an air-over-liquid tank to do so, or have some type of gear driven oil pump to do so.

https://youtu.be/_Xq6MmiKuqY
I have started many old engines. The older they are the more easily seem to want to live again.


https://youtu.be/tBmAaAd7fkM

What a junker!

I would steer clear of taking anything apart or off as well.
Many moons ago, I worked at an engine replacement shop [not for long, mind you]. Before starting any of the engine up for the 1st time, we used a oil pressure tank, similar to a brake bleeder, that connected to the oil gallery via the oil sender unit port. From here, once connected, the primer would inject oil into the vital parts, main bearings, rod bearing and such. We would also hand-crank the engine to allow the oil to wet the lower rings which are typically your oil control rings, this will apply a little bit of oil to the piston skirt.

I would be careful shooting oil into the top of the cylinders, if you do, make sure there is no fuel source in case of accidental start-up to prevent a diesel run-on. Last thing you want is for your truck to start and hit full throttle with no oil pressure.
If you decide to squirt some oil in the top of the cylinders, I would use the starter to crank it over a few times to clear out the cylinder then connect the fuel line or remote fuel line.

You can get the primers at some pro-shops or places like Summit Racing. Probably not too many people have one on stock. You can make one with a high pressure electric pump and a reservoir as long as you have the correct size fittings to plug it into the oil gallery port hole.

Good Luck!

http://www.steelsoldiers.com/attachment.php?attachmentid=525473&d=1415302265 let's see if that works.

Monkeyboyarmy said:

My local diesel mechanic said most likely you will won't get oil pressure from spinning the engine over.

Click to expand...

I was cranking over my NHC250 today with no fuel and the oil pressure rose to 90psi.

I'm in the "do not disassemble a perfectly good engine" crowd.

i'm also in the "keep a close eye on the fluid levels until you're confident the seals and gaskets are not dryed out and leaking" crowd.

Here's my recent experience with a couple of 250's. Bought a 2010 rebuilt 923A1 that i swear didnt have 200 miles on it with a "burnt starter". It also said RIP on the windshield. So I knew there was a chance that it was locked up. Got it home and sure enough the engine was locked up. Now before this truck, I got to work on a 944A1 with 450 miles on it. Complete truck but motor was stuck. I noticed that every time I bumped the starter, the fan would jiggle. I bumped that starter for 2 days and finally it broke free. Got fuel to it and it fired up and ran great. Been running good ever since. So back to the new truck. Put a starter in it and started bumping it. At first, nothing. After about 2 days of this, it started turning over. Spent another day turning it over as long as the slaved batteries would last trying to get oil pressure. Never came up. So I decided to put fuel to it. It fired once for a couple of seconds and the second time for about 5 seconds before....you guessed it....it locked up. I kinda figured the 944 had stuck pistons but I am not sure about the 923. Could be bearings....haven't pulled it apart yet.

So 1 more part to this story. I found a couple of 250's in Ga. that were supposedly rebuilt in cans. The did have some new gaskets and parts including fuel pumps, starters and alternators. And they were offered to me at scrap prices. The fluids were drained in 2011. So I knew they would be pretty dry. So I got one ready to start by installing an oil filter and oile. Engine turned over OK but maybe a little slow. I tried for a couple of hours to get oil pressure up but got nothing. Every time I turned it over, it seemed to get slower. I needed to get oil flowing. So the first thing I did was to turn the oil filter canister so that the drain plug was up. I added a couple of quarts of oil to it. I then attached a grease gun to the side of the block in the oil passage next to the gauge. I filled it with oil and pumped it in (very tedious). I did this a couple of times but still got no oil pressure. So I decided to crank it some more. Still no oil pressure but I didn't think it was turning over fast enough. So I pulled the valve covers, tightened each exhaust valve 1 turn and spun it over. Without compression, it obviously turned over fast. 10 seconds of turning and BAM 50 pounds of oil pressure. Turned it over some more till I got oil to the top end. Reset all of the valves and closed it up. Added fuel and fired it up. What a super running engine and 75 pounds of oil pressure. Now had I had a higher volume pump and mdmorgan's post, it might have been a little easier. But definitely pr-lube the engine if you can. Thank you, and good night.

You can also build a simple pre-lube device from a small Freon tank, and a couple of air fittings/valves. Fill jug 50% with oil, pressurize it, flip it over, connect it to the oil sender port, then open the valve. Air pressure will push the oil into the engine.

Did they keep the headlights? Love the part where the gauge falls down inside in the dash opening when the camera comes around. Wish I was there, it's a riot to crank up old treasures. I hit the starter for 1/2 a second on an old Detroit Diesel 6-71 to see if it was locked up, and it started (no fuel line hooked up) and wound up all the belts, hoses, and rags around the fan. Too bad no vid, you'd be laughing so hard the breakfast would fall out of your mouth. I was running around like hot coals were poured down my shorts.