What's wrong with this NHC 250?

[WildernessJeep]

As many of you know, I had a sleeve slip on my 1984 M936 Wrecker with a NHC 250. Honestly the motor ran perfectly until then. I paid a guy to do an in-frame to replace that sleeve. He had it purring like a kitten. It again ran perfectly. Then I drove it ten miles and slipped two more sleeves. So they pulled the motor and did a complete rebuild on it. Now is sounds like crap, and I'm missing about half my engine power. Frankly, I'm past this mechanic's ability. He had the heads rebuilt out-of-shop, and I think the lower half is good. I've pulled the head covers and confirm that each valve is moving (none stuck) as they should. But the engine still sounds like shit. It sound horrible under load. It sounds less cringy once it is warm. I can hear a notable "thwop-thwop-thwop" at the intake and exhaust, which tells me a cylinder is misfiring. Replace/rebuild the injectors is my next step, unless you, the almighty hive have a different theory. Cold start video in link below:

https://www.facebook.com/video.php?v=3363845950410754

 

[simp5782]

Get the truck to operating temp. Then idle the truck at 1300rpms for 2 mins. Leave at high idle. Using a thermal infrared gun shoot each exhaust port for each cylinder and see which one has the lowest temp or temp greater than 10 degrees of any other. That is where you start

 

[WildernessJeep]

Okay, so I followed SImp's advice. The header temps are as follows:

Cylinder 1: 370-390 degrees
C2: 370-390
C3: 370-390
C4: 180
C5: 370-390
C6: 240

So maybe I have two bad cylinders? Or do you think it is timing?

 

[simp5782]

Unless they replaced the cam then they did not mess with the timing.

Pull the exhaust manifold and see if those ports that are low are wet or dry compared to the others
Don't think it would be a valve set issue. Can pull an injector and see if a tip is cracked.

 

[WildernessJeep]

What should the timing be? How to confirm it is absolutely correct?

 

[simp5782]

I doubt they touched it. It takes a special tool. Its around $1200 and obsolete. If they did an inflame they left the cam and rocker boxes alone. If they didn't replace the cam then the timing wouldn't mess up cause they didn't reshim the boxes

And it would be paired cylinders misfiring. Not 4 and 6. Each 2 cylinders have their own follower box 1 and 2 would misfire together cause the timing is set off the box shim.

 

[simp5782]

 

[dmetalmiki]

IF EVER...I heard an engine (Any engine!) Fighting to much advance...You have one!
TIMING..tools special or not, hard to do, (Or not) too this that and t'other..I'm 100% positive that engine is way way advanced. (The delay period is WAY out!).
And, It almost sounds as though the injector timing (Firing order)was done via a random "Lottery" machine.
My advice (If it were mine) Would be to stop messing around with it, and get the help of a diesel engineer mechanic with experience of that type of engine and ancillaries.
Please keep us informed of the malady found, And, The (eventual 'fix').
Oh, And DO NOT (Attempt to) drive it like that.
Good luck, I hope you find an expert on the Cummins NC250 set up.

 

[WillWagner]

I don't have FagBook any more. Can you post a direct vid or one thru YouTube? Can't hear a timing issue, it would be a visual/olfactory thing.

 

[WildernessJeep]

It is at a shop now that agreed it was the timing and should be an easy fix. Monday will tell.

 

[WildernessJeep]

Update: Yes it was the timing. It took them three tries to get it right, but now all is well. The truck runs fine and it is normal. Standby for hurricane Delta.

 

[Crf450x]

Can you repost the video? I’m just curious what it sounded like...

 

[WildernessJeep]

Can you repost the video? I’m just curious what it sounded like...

The file is too big for Steel Soldiers. Facebook is the best I can do.

 

[Steelreaper80]

The file is too big for Steel Soldiers. Facebook is the best I can do.

Don't have Fakebook. Can you upload to YouTube?