New here and wrenching for the first time on an 86 190e 2.3

Compression test ranged from 110-135. Lowest compression on rear cylinder.
Flushed crankcase, new oil and plugs and is running smooth w/145k.

What is the acceptable range for compression? Couldn't find any data online.

Thanks!

 

Hi,
Its the difference in values that is important. Ideally all cylinders should be the same.
A specific value is difficult to state since crank speed, engine temp, gauge accuracy, test consistency between cylinders, time from last engine running etc will all impact the nominal value.

IMHO a difference of greater than lets say 10% between cylinders indicates all is not well.

Stuart

 

Thanks Stuart-
This car seems to run fine now with just a change of plugs/oil.
I used a very old Snap-On gauge with crankcase fluids drained.
Was expecting to find a dead cylinder as one mechanic had diagnosed, but this is not the case.
-Rob

 

I have driven a few cars until they simply wouldn't run anymore, and it seems to me that when compession gets below 80psi, the fuel will not ignite at all, below 100psi is low power. Ideal is between 125 and 150, with all plugs out and a good battery.

 

Snanceki is dead right about the differences. The differences will make te engine run "rough".
In th old days, each valve could be adjusted with tappets for a race balanced engine.

Make sure you don't have a leaky injector thinning out your oil with fuel.

 

A cylinder leakdown test will tell you more-the instrument isn't that expensive-especially against the cost of a MB. However, as I found out recently, even that isn't enough to test for a blown head gasket-that requires the addition of a block tester.

Providing your battery is fully charged, your metering block fully open and your spark plugs removed, you should get good compression readings. The differences between the cylinders is key, because gross variations can mean worn valve guides or rings etc.

 

Thanks-
I haven't got the paperwork on the car yet, so it will be some time before I get to see how it behaves on the road.
Turning my attention to the driver door power window/lock. Power to the switch, but no up/down yet.