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Good work!

I’m sure you’ll get it figured out. Tomorrow’s a new day. A cup of coffee in the morning and it’ll be running in no time!

Do you believe that the fuel rail is moving freely? Does the engine sound like it has compression when it’s cranking over? It’s apparent that you’ve had several of these units before.

It sure sounds like you’ve got the oil pressure issue resolved. Have you replaced both of the fuel filters yet? You could very well have a restriction there. With the S1 in the run position you should have a steady stream of fuel returning to the tank.

I too learned from reading the TM last year when I torn into that DN4M with the bad pistons/rings. It clearly describes how to bolt down the rocker arms like you just wrote about. Without reading that information in the TM, I could have easily done some damage to an engine that I just finished...

So, on this topic what's the risk of piston to valve interference when the oil pressure relief valve is stuck, thus causing bent pushrods, bent valves etc? Have you seen this on the DN2M, DN4M engines?

Ray! Great job on this my friend! You're obviously speaking from experience on this too. I had no idea that the oil pressure relief valve being stuck could cause the lifters to pump up, causing the valves to not close all of the way, thus a no compression situation. I definitely learned a bunch...

This is true!

Got it. I always try to be respectful of others educated opinions 😁 On the topic of seized piston rings, this was mentioned as the cause of piston failure on the DN4M engine that I was working on last year. Nobody ever said what the possible cause of piston ring seizures on these engines is?

I believe the 802A and 803A units use the same internal engine parts. https://www.steelsoldiers.com/threads/dn4m-pistons.208238/

It may be another case of piston ring seizure. I had an 804A unit this past with low compression. When I tore this engine down, I had 3 out of 4 pistons with ring seizure, the piston crowns were literally wiping themselves off on the cylinder walls. I was able to get the 3 pistons, rings etc...

Unfortunately, if the lifters were pumping up solid, the valves would be hitting the piston crowns. Just speaking from experience here.