I just acquired a rebuilt engine for my 84 300SD. It came from an 82 300SD and the engine appeared to be locked up when I first got the vehicle. After pulling the engine and transmission I discovered that the transmission had locked up while the car was in motion effectively destroying the flex disc and torque convertor which also locked the engine up. After removing the transmission the motor turned freely and I assumed it to be O.K. and performed a compression test on it. Two cylinders had compression, three didn't. I pulled the head and found that the P/O had not properly adjusted the valves on the three bad cylinders and the valves had carbonned up preventing the valves from closing, hence no compression. I cleaned up the valves and replaced the stem seals. I replaced the head, adjusted the valves and checked compression again. This time all 5 cylinders were good. I thought I had a good engine and installed it in my car. The IP I installed and then did a start of delivery check and it appeared to be OK. But the engine was very hard to start and smoked like crazy when it finally started. I again checked the start of delvivery and it had changed to about 37-40 degrees before TDC instead of 24 at which I installed it at. I removed that IP and installed the one from my old engine (which I knew to be good) and the same thing happened. Could the injector timer behind the vacuum pump be bad? I am at my wits end. Any and all help would be appreciated.

That's what it sounds like. I thought those advancers were rather bulletproof. You may be in for a new timing chain, front seal, etc., to get in there. Let us know what you find out.

PETE

It's a mechanical device. Like everything man-made, it can break too.

A sudden stoppage can take its toll on a great number of things, especially on items with a fair amount of mass and any moving weights. I would start with the chain and the ip drive. I would also check the balancer and its pins.

As a follow up to my original post, when I had the head off this engine I noticed that it had new pistons (.05 oversize) and showed absolutely no wear at all which means that it had not been run very much. Also, no chain stretch at all and the chain looks to be new also. I guess that sudden stoppage did in the timer. I'll pull it out and check it and let you all know what I find. Thanks for the helpful advice.

as per Rick.

I second that.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)