I did a compression test on one of my om617 engines, it has about 260k on it but has a injection pump problem.

here are my results from a cold engine sitting over night, valve adjustment was done 20k ago

1- 400 psi
2- 420 psi
3- 360 psi
4- 380 psi
5- 360 psi

my question is that with a good injection pump and all timing set correctly, do you guys think this engine will have good power and idle smoothly as it should?

thanks

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

The spread of 60 psi is too high between the highest and lowest cylinder. A good compression reading should not vary by more than 10%.

In my opinion, though you have good compression throughout all the cylinders, the high spread could cause the engine to not run smooth.

I would do a valve adjustment and test again. Hopefully the spread will be lower.

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1983 123.133 California
- GreaseCar Veg System

Always check compression after a fresh valve adjustment. When you do the valve adjustment, note which valves were out of spec and see if they correlate with the compression results.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Those numbers will result in a lumpy idle and probably hard starts/misfires when really cold. It should be alright down in Florida though, by cold starts I mean below 0 F.
I imagine it will run just fine with everything else spec'd properly. Rebuild the pump will ensure it is as smooth as can be.
Power will be fine, if the engine starts on its own it will have decent power provided the pump is set up. It might be a touch smokey though.

Mercedes compression spec for a new 617 engine is 320 to 350 psi @80 degree C coolant temp.

Your cold numbers is already higher than spec and the variation between cylinders is out of spec.

It could be:
1. your compression tester is wrong
2. your compression tester is right and the high readings are due to lot's of carbon buildup in the combustion chamber, raising the compression ratio.

You may want to do the test again with engine at 80 deg C coolant temp.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

...or the battery started to get tired or the starter motor was too hot after cylinder #2...

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

To test that theory, reverse the order next time.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked