OM 617 compression test results, cold engine, non-running - PeachParts Mercedes-Benz Forum

BenzDiesel · #1 04-19-2006, 04:20 PM

Cylinder test dry:
1- 300 psi
2- 300 psi
3- 300 psi
4- 300 psi
5- 200 psi

Number 5 cylinder after a squirt of oil- 250 psi and after continued starting, pressure dropped to 150 psi. The engine is a 1981 SD with unverifiable mileage. I started the engine a while back and it had no power and billowing white smoke exited the exhaust, so I pulled it and let it sit. I did an initial fuel timing test recently and I know it is off, but my concern is with the 200 psi and whether the 300 psi will enable the car to run satisfactorily, when the specs call for upwards of over 420 psi for normal specs (348-435 to be exact), although I don't know if these are hot or cold numbers, but 300 is a long way from 420. I'm in the process of considering dropping an OM617 into my other 300SDL and hope I can get the car running in order to get it out of the yard and recoup some of my costs from having bought an OM603 powered car and had to go through the OM603 learning process. Any thoughts on these numbers will be appreciated. I'm going to run some compressed air through #5 cylinder to see if I can find where the compression is leaking.

BenzDiesel

t walgamuth · #2 04-19-2006, 06:38 PM

the numbers for a cold engine are about right i think. the figures up near 400 are for a warm engine.

the 200 is below recommended for even a cold engine.

it could just need a valve adjustiment. the blowing air in will tell the tale.

good luck.

if it needs major work i dont think it will hurt to drive it the way it is for a while while you save money up for the work. it will just shake more than usual.

tom w

Diesel Giant · #3 04-19-2006, 07:52 PM

Yes adjust the valves and redue the test. It can have an affect if they are way off.

Iva Biggen · #4 04-19-2006, 08:48 PM

You are allowed a max of twenty percent differential on compression readings on that engine and Adjusting valves will give you some knowledge but the fact the compression came up with oil induced into the cyl and the fact you stated it had bellowing White Smoke before you set it up would indicate a bad cylinder and maybe a cracked head from Overheating before you got it maybe .I would not go to the troubble of putting it in anything until these issues were looked at .

BenzDiesel · #5 04-19-2006, 09:30 PM

I've just finished all the tests that I will do. The exhaust valve on #5 cylinder was somewhat loose and gapped more than the .014 mm that I used as the spec number. The intake valve was pretty much .oo4. I then performed the compression test again after checking the valve timing and got the same 200 psi, just as before and I didn't bother to oil test it again. I then hooked up the air compressor to the
#5 cylinder and while holding the bolt on the crankshaft to keep the engine from turning backwards once the compressed air was applied, I listened for seeping air. I heard air escaping from #5 at the air connection area. I heard air very pronounced coming from the intake manifold, however, I still had the egr still connected and wasn't 100% sure all of the air was coming from the intake only, but I plugged the egr entrance hole leading into the intake with my thumb and felt no noticeable air, but the air was still coming from the intake very noticeably as I listened with a 2 and a half foot piece of metal fence post that I used as a stethoscope. I also heard air escaping from the timing chain area and most people in the know say that is the rings leaking, but the leak was less pronounced than at the intake manifold. Anyway, that is where I am in the process. The car still looks good, as I washed it, to see if it would help make me want to invest the time, money and effort to then give it away to a new owner. And it is certain that the engine will fit into the bay correctly to include perfect matching of the motor supports and one of the motor shocks, and it appears that a few modifications will allow the engine to bolt up without too much problems, just looking at it sitting there, when the transmission from an OM617 is bolted up as well, as I have it. One question however, does anybody have a car with a dead cylinder in terms of the specs and the car is still drivable?

Quote:

Originally Posted by Iva Biggen

the fact you stated it had bellowing White Smoke before you set it up would indicate a bad cylinder and maybe a cracked head from Overheating before you got it maybe.

Iva Biggen, come to think about how the engine ran when I first attempted to use it, it did run hot or at least the temp gauge would rise and I would shut it down before it overheated, but the damage was probably already done, as you reasoned that it was a good candidate for having been overheated. The repair to the "probably" cracked head will probably cure that engine, but I'll still have to run the situation through and through to decide what to do next. I don't need the car for transportation and have other diesels that I use.

BenzDiesel

JimmyL · #6 04-19-2006, 09:53 PM

Seems like I remember a forum member that on his 240D he had very low compression on one cylinder. Very low compression. With only 4 cylinders his little car sounded fine, and I don't remember allot of smoke.
As long as you can get the smoking resolved you can just see how it goes. If it remains a smoker it isn't worth fighting through, and you would certainly want to intervene....

t walgamuth · #7 04-19-2006, 11:03 PM

could you give a little more history on the car? had you driven it before it sat? and did it act up then too? or is it just doing this after sitting?

tom w

BenzDiesel · #8 04-19-2006, 11:38 PM

Quote:

Originally Posted by t walgamuth

could you give a little more history on the car? had you driven it before it sat? and did it act up then too? or is it just doing this after sitting?

tom w

I was gambling and bought the engine on the blind, based mostly on looks and the replacement parts the previous owner used to maintain the car and on the Mercedes Benz "advertisements" I saw on tv and the high prices they charged for their cars and all that other stuff I had heard about a Mercedes diesel engine would go A MILLION MILES and just "assumed" and was hoping that for that much money (paid by the original owner), the engine just had to be good. I originally had planned to use the engine in my 1983 300SD, but when it didn't work, I pulled the engine from my 1982 SD and scrapped the body and took the best of both SD cars to make one decent car. I'm now looking to use the OM617 engine in a 1987 300SDL that originally had the OM603, since I now know more about these Mercedes diesel powered cars than I did a few years ago, when I first got a Mercedes diesel. Also, at 85 mph (fast as I want to go anywhere) and the music playing, I can't tell that much difference between the OM617 and the OM603, except that the 603 has a smoother sound and a little more get up than the 617.

BenzDiesel

t walgamuth · #9 04-20-2006, 09:20 AM

well, based on what you have told us, i guess i would be thinking of having the head off. i suspect that the problem may well be confined to the head. if it were rings and normal wear they all would be low. could be a broken ring or a holed piston, but probably a bad valve is more likely.

tom w

BenzDiesel · #10 04-20-2006, 09:50 AM

Quote:

Originally Posted by t walgamuth

if it were rings and normal wear they all would be low. could be a broken ring or a holed piston, but probably a bad valve is more likely.

tom w

I really do hope it is as simple as a bad valve. I have a known good head that I tried to sell for $100.00 in the Parts Section a while back, but nobody bought it. I'll probably take the head off and check it out further and use the better of the two heads. Thanks for your thoughts.

BenzDiesel

biopete · #11 04-20-2006, 12:16 PM

Quote:

Originally Posted by BenzDiesel

One question however, does anybody have a car with a dead cylinder in terms of the specs and the car is still drivable?

BenzDiesel

My compression test thread is here -- a 1981 300D OM617. http://www.peachparts.com/shopforum/showthread.php?t=148465&highlight=Compression+test

My weakest cylinder was 250 warm. I have tons of blow by and lots of whitish gray smoke. But when I run B100 i dont see any smoke. I 'm going to clean injectors good and see if it helps. Which leads me to believe the smoke is not coming from water. But your question was does it run fine -- Yes. For an NA they say it has normal power -- cruises at 70 and 80 great until it hits a hill. . It wont start in cold but there is no block heater and starter is weak and finally the solenoid needed a huge beating to start last night.

Does yours start in the cold?