In discussions here it was presumed that my engine failed to restart after sitting overnight because it ran out of oil the night before. I did a cold compression check (obviously) and found bad results. The first figure for each cylinder is dry, the second is with a little oil injected into the cylinder: #1 150&170, #2 100&200, #3 140&170, #4 200&200.

Here is the question: If the rings/cylinders got screwed up by lack of oil why wouldn't the compression increase dramatically by putting oil in the cylinders. #3 responded like it had bad rings but the others did not.

A few questions:
*What is the reliability of the Harbor Freight gauge?
*The car ran great when turned off. Assuming that oil I put in the cylinders during testing would seal as well as rings in a hot engine would, and the rings did get damaged, how would one expect an engine with hot compression of 170-200-170-200 to run?
*If a worn (low compression) diesel was cranked for a long time, could the injectors inject enough fuel into the cylinders to effectively wash the oil off the walls and prevent compression/combustion? Thanks

If the tension against the cylinder walls by the rings has been reduced by overheating them. Or the sharp ring edges softened with the heat and no longer very effective. The combination of oil and weak or damaged rings is just not sealing enough. You seem to be below required starting pressures with your compression check unfortunatly as well. Even with the oil added.
If this car had a stellar performing engine before your event you might just re ring it if really lucky and bearings are not damaged. . Since it was a new aquisition that probably is an unknown. Best bet now is to locate a good used engine if possible as inexpensive as possible if you want the car. We apparently had a bad case this week in my neck of the woods. A members engine seriously overheated with a malfunctioning temp gauge and his engine is toast. Never nice to hear.
As for checking out the calibration of your harbour freight gauge. If you can find or have a air compressor that shuts off at say at 175 pounds. Figure out a way to couple the gauge to it. If the gauge reads about 175 that is enough of a general calibration check. Others might have better ideals. Sorry to hear the probable bad news.
The only break you might have had was you think you saw oil pressure all the time with 5 quarts low. There might have been just enough oil available to protect the bearings. I also think the addition of motor weight oil to the cylinders for testing gives a better seal than normally available. You really want to see 200 lbs across the board preferably more with no oil addition. For a chance of starting. Opinions from others that have owned diesel engines with marginal compression might give some guidance here. There have to be some members out there that have nursed their engines to the bitter end. They will know the end point of viability far better than myself.

Scary that your 240D was running fine one day and then not at all the next. The only time I have had a problem with mine not running is when I had a small fuel leak and air would get in, preventing the pump from sucking the fuel in.

If you actually ran it out of oil and scored the cylinders, and you have compression numbers that low, I can see how it wouldn't run. I'd tow it to a diesel shop and have them test compression with their gauge just to double check. Or maybe, have them check your gauge against theirs (on some vehicle in their shop) if they're willing.

It would make sense to me that a lot of unburned fuel in the cylinders could wash down some of the oil but if you put a little bit of oil in now thru the injector holes, I imagine that would fix it (at least that concept worked for me on a lawnmower engine). BTW, have you tried push/tow starting? The higher rotation speed might just get it running. And I'm presuming you've checked fuel delivery at the injectors?

-AC

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1976 240D "Katja"

I know engines are hard to come by (I've been looking). Can't see sinking another $500 to $1000 into it because neither the MPG nor the performance specs were stellar, the MPG actually being less than a gasoline vehicle of the same displacement. Thanks for the advise. Does this site have a place where I can advertise this for parts?

Katja,
I did find a little hole that spurted fuel but only when I used the priming pump. I temporarily fixed it so no air could be sucked in. I think I have a compression problem. The last thing I am going to try before junking/parting it is to get it to fire with a little oil in the cylinders.

I think you have a worn out engine. I also think you cannot cause major wear on rings and cylinder walls by running low on oil. Primary low oil damage is always found in or on the crank and rod bearings first. And that will stop the engine long before you can get cylinder wall damage. Cranking a non running engine will not cause major wear. Even if there is a washdown of engine oil on the cylinder walls by the injected fuel, that fuel is also serving for a lubricant between rings and wall

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

I just got it running. I put oil in the injector holes during the compression test, which upped the compression, reinstalled the injectors, primed the system and it started.

Now I have a knocking that was not there before. I have a lot of experience with gasoline engines and it sound like the rod knock noise I'm used to hearing, except unlike the knocking in gas engines where, when you goose the throttle a little you hear, rat-tat-tat-tat-tat, this knock is at idle. It is irratic. For example when idling at 600 RPMs, you might hear it knock once, then again a second later, then 4 seconds later, then 2 seconds later. It decreases when you add about 500 RPMs and disappears (at least you can't hear it) when you rev the engine and hold the throttle at 1/2 to 3/4. I got a ton of blow-by probably, mostly from cylinder # 2. It almost blows the filler cap off. Based on the tons of oil in the air cleaner and at the intake, I know now the blow-by was there when I bought it. As for the knocking, I heard an occasional knock on cold startups, but there were only two or three individual knocks during each episode, then within 30 seconds it would be gone. Any idea what this could be?

That is called nailing, it is caused by dirty/worn injectors

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

I have braided cloth fuel lines that run between the injectors. Some are not sealing properly after I pulled them off to remove the injectors. Any reason I could not replace those with rubber fuel line of the same inside diameter?

that will work but the lines will not last as long as proper braided line from your favorite mb parts supplier or the dealer, and the good stuff is not expensive either,

a good running diesel should get about one third better mpg than a gasser in the same application. overall,,,,about twice as good around town and maybe ten percent or more better on the highway.

good luck

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.