om617 compression test results
 

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

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.

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.

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.

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

To test that theory, reverse the order next time.