Just a long shot but maybe your AC compressor is stuck on and siezed? Would cause drag on the belt as you attempt to crank the motor.

wellll, IDK about turning the engine with a 1/4" ratchet, but it should not be difficult with any decent ratchet... probably in the 20foot lbs pressure range. if you can't turn it with the GP's out, and the belt disconnected, the next thing I'd do is pull the starter.

A seized accessory is a posibility as I remember he quoted some smoke under the hood. Or the smoke may have just been a figment of my imagination. I am not going to go back and read the thread again.

Other than that a turned rod bearing becomes an unfortunate possibility as well.

Barry
Are rolled rod bearings common in the OM603?
I had A '57 Dodge panel many years ago that "rolled" a rod bearing -and this problem I'm having with my SDL is almost identical, except with the Dodge it just happened out of the blue (I was later told that that engine is prone to rolled rod bearings), and with the SDL the problem was immediately preceeded my a broken fuel return line.

Accessories all turn when I rotate the engine by hand. I also removed and tested the starter and it seems to be running fine.

Turning engine by hand with the glow plugs out takes about 70lbs with my torque wrench.

something's restricting your rotation
 

70Ft Lbs to rotate a OM603 (With it's GP s OUT) is an awful lot of force...

And to answer your question,NO the OM603 s are not noted for Spinning Bearings.
(But Extreme Low (Or No) Oil Pressure will "Spin One" @ Highway Speeds
in a heartbeat.)
[I've never heard of a "Quiet" Spun Bearing,usually they're Screeching At You.]

As someone here already stated I would check and make sure the starter solenoid is not still engaged as well as loosening all accessory belts to check for any seizure of one of them. How is the oil level ( I know it is not at temp etc ) it should at least be on the dipstick.

Not enough information just because the accessories turn with your heavy effort as well. Remove the surpentine belt to check each one individually for excessive drag. You have to be sure before moving on. No the 603 is not notorious for turning a rod bearing. This does not mean it cannot happen. All that is certain at this point is that there is far too much drag present.

"As someone here already stated I would check and make sure the starter solenoid is not still engaged"

Starter has been pulled and works fine.

"How is the oil level ( I know it is not at temp etc ) it should at least be on the dipstick."

Oil level is good.

Barry -I removed the belt and now the torque is closer to 50lbs -all accessories spin easily individually. There is a squeek from inside the engine while turning.

A single Squeek?
 

"There is a squeek from inside the engine while turning."

If you could rotate the engine at say 250 RPM would it be a LONG drawn out Squeek?

(Un-Lubricated Surface, Bearing?)

"If you could rotate the engine at say 250 RPM would it be a LONG drawn out Squeek?"

I don't know -but when the engine "seized" on the freeway there was no noise or irregular firing, just increasing power loss over the course of 2 or 3 minutes, stall, and slow rotation -with no squeaking -upon my attempt to immediately restart it.

I wonder if there is any possibility that my cylinder walls have been "coked" from bad fuel or overheated oil or something? This all did start with a fuel problem. Anyone had any experience with coked cylinder walls?

How bad an idea would it be to inject a LITTLE "Sea Foam" into the glow plug holes and (leaving them out of course) rotate by hand to see if that frees things up any? I'd rather that be the problem than a spun bearing I think.

If you're gonna "Soak" the Cylinders (Sans G.P s)
 

No Seafoam !!!

Kroil or Aerokroil
http://www.kanolabs.com/

Remove G.P.s. Fill cylinder with Kroil. Let sit as long as possible(2-3 days)
Then use the Starter to rotate the engine and Blow Out the Kroil (Rags,Rags,Rags). Change Oil+ Filter. Re-Install G.P.s

'Can't hurt

(But,I'm afraid to mention that it's beginning to sound like a Lubrication Failure.)

The return hoses leaking on the injectors have no possible bearing on the excess friction problem unfortunatly. They are two absolutly separate issues.

Hearing a squeek with the accessory belt off when turning is not the best.

A semi seized injection pump is also another possibility but almost never happens. I do not know the layout of your engine but if possible with part of the oil pan removed you might establish the location of the squeek. Best attempted with two people.

Thanks Compress -I tried it out and turning the engine by hand IS easier -now around 30 lbs and dropping. I'm hoping it's bad fuel glazing and not oil related. I have always been consistant about changing the oil and filter, but I am not sure about the guy who had it before me. One clue to the fuel glazing possibility would be that I have never let the car get below 1/8th of a tank except on that day. Maybe there was something nasty just waiting below an 1/8th of a tank?

"The return hoses leaking on the injectors have no possible bearing on the excess friction problem unfortunatly"

Yeah -it's starting to look like this situation could be one of those virtually impossible mechanical coincidences, unless it is the scenario I outlined above, in which the the link would be the leak dropping the fuel tank level down to where something nasty lay waiting to be sucked up into the system.

Oh -and the squeak has subsided along with turning the engine by hand getting easier.

Take off the fuel cap and smell for gasoline. Just a thought.