1985 300sd wont turn by hand.
 

I have an 85 300sd turbo diesel, I accidentally ran it out of fuel due to the fuel guage being broken. I cracked the lines going to the injectors, I was ably to get it to start it was running really loud, almost as if the exhaust was off. I'm thinking it was because i didn't get all of the air out of the system. it died again and i bled the lined again just to make sure. I was able to start it again, still with the rough sound while running then it made a louder bang and stopped instantly. now I am not able to start it at all. It sounds like the starter is grinding. I tried turning the engine by hand with a 1-1/16 socket and breaker bar and it is completely stuck. I removed the injectors and tried again to no avail. after reading a bunch in the forums I thought it might be the starter locked up. so I pulled the starter and tried to turn it again. No luck, still stuck. the car ran really good with no problems at all before I ran it out of fuel. I don't know why it would choose that exact time to fail considering it was a strong running vehicle before hand. I checked the oil as well and it wasn't low at all. any help would be greatly appreciated. Thanks - Randy

Pull the valve cover and check the chain.

forgot
 

forgot to say i checked the timing chain as well thanks though

Sorry, but I'd suggest that your chain jumped a tooth or two and bent a valve. If you can't turn the engine and the camshaft looks ok that's probably a bent valve. The exhaust sounding loud may be from the cylinder firing and a premature opening of an exhaust valve. Usually, a piston won't stop the first time it hits a valve but the second ping brings the entire rotation of the engine to an abrupt halt.

also, what size socket is needed to remove the injector pump? a mechanic friend told me to check to see if it will turn with ip off to see if ip locked up.

Last time I encountered a car that I couldn't turn by hand, it turned out that one of the piston rod broke and blocked the crank, thus stopping it from turning.

Take off the oil pan and look at the crank, see the conditions.

A borescope might come in handy about now. I don't know of mine (Harbor Freight) will go thru the glow plug holes or not but it might. Anyhow, that will let you see what's going on between the piston top and the cylinder head. You could look in thru the injector hole but I think you would have to pull the prechambers - a job I've never done so no help from me on that front.

You can also drain the oil (gonna have to do that anyhow) and poke the borescope in the bottom end to see what's going on down there. Modern technology is a wonderful thing.

With the price of our engines these days it's cheaper and easier to swap in a used engine if it's anything serious. I just paid $250 for a back-up engine for the race truck which is truly a bargain.

Dan

Is it possible that the engine did not run out of fuel, but had a mechanical breakdown that stopped it dead in its tracks?? There really is no reason that a perfectly running engine that runs out of fuel would suddenly start running loud, and then seize up when being restarted. The fact that you got it restarted may have aggravated the original issue. Good luck.

With a "locked" starter you will still get some free play in each direction. Even if the starter stuck engaged, the engine will still turn.

Even with a jumped chain and bent valves, the engine still should turn. Pull the valve cover and have a look for loose - displaced cam followers / rocker arms. This would be a symptom of a jumped chain.

A stuck injector pump won't cause this as you will still have free play.

Remove the valve cover and look for damage.

Remove the vacuum pump and look for damage.

It sounds like something is stuck in the timing chain.

The glow plug holes just extend to the side of the precombustion chamber.
The injectors just sit on top of the precombustion chamber and look at the pintel and the radial holes... very small holes... which go to the top of the pistons...
ONLY pulling the precombustion chambers allows you to see the top of the pistons... other than pulling the head off the engine..

NOTE.... you have to pull the glow plugs out BEFORE REMOVING the precombustion chambers or you will mess up everything... the glow plugs are like a locating pin in a wood joint. not permanent but if you FORCE the joint apart without pulling the pin you will cause all sorts of damage...

I haven't read of a case where running out of fuel, or air in the fuel tubing, could damage the engine. I concur that likely something else mechanical happened and perhaps at the time you were low on fuel, but only by coincidence.

x2.

I suspect it happened when the engine was running rough, may be on 4 cyl or less, and damaged the engine. OM603 engine could NOT jump a teeth, it is restricted mechanically. I would expect it is the same for OM617 but don't know. If you cannot turn the engine with all the injector removed then the engine may be done for, something very mechanically wrong internally. Taking off the valve cover and look at the cam would be the first step. Good luck.

Thanks, 'Mang - great info. As I said, I haven't been that far into mine but the concept of using a borescope is still a good one. Now that I think about it it makes sense that the glow plug would be in the prechamber. I'm used to Mexican hat chambers and I'm still getting used to the Mercedes design.

I suspect the OP is at a point that pulling the prechamber is NOT the biggest job he has to face and it might be a good diagnostic step.

Dan

I figured out what the problem was. I threw a rod.