Checked compression today...
 

Did a compression test on my 300D. Warmed up the engine to the operating temp. Let it sit for a little while until I was able to handle it. Removed the hard lines, glow plugs. Reamed them all out - was meaning to do that for awhile - they were REALLY carbon-packed...

Started doing the compression test through the GP holes, but quickly realized that the space is too tight in there so switched to Injector holes and continued. Replaced the heat shields as I re-installed each one. Anyway, here are the numbers (psi):

#1 350 350
#2 320 315
#3 300 300
#4 300 305
#5 305 305

Think these numbers are pretty good - wonder what others think... Was under the impression that anything above 220 psi is within spec.

It was a little concerning to find some oil around the injectors and heat shields when I pulled the injectors off... Also #2 and #4 GPs were oily and wet... not sure if that's normal - but I guess since the compression is not perfect maybe it's just the way it is.....

i was under the impression that anything above 320 was alright, not 220

220 isn't even enough for the engine to start. My 240's 616 had 200-250 across the board and it wouldn't even start with ether.

I would say that it is not real good
 

I think real good is another 100 plus pounds up, at around 425 with very little variation. I think 305 to 315 is way too low. How about the valves. Have they been adjusted recently. You might find a valve adjust will really change things.

I'd say their fine. Numbers are going to be lower at your altitude. My SD showed around 330psi dead cold and it runs fine. I think MB says 220 is a minimum to run.

what fitting did you use

I agree. My engine is 320-350 and can start at -20*f with only glowplugs.

Fitting...
 

Used a Compression check tool for diesels from Harbor Freight (around $35)... it has a number of fittings that you can choose from...

You can check it thru the glow plug holes using the 90 degree fitting in that kit.

My book says 220 cold minimum.

Oil on the gp's doesn't sound good, did you brush them on something when you removed them? A little oil leaking from the cam cover is quite common.

Hey all,

What is considered oil on the GPs? Actual oily buildup? I took out my old loop style plugs last week and they were black, but not oily per se.

Black is burnt carbon, normal.

If it starts and runs OK, and you've adjusted the valves recently, why worry? It's silly to re-ring, rebuild or replace the engine, (corrective action for low compression) isn't it?

if you reamed the glow plug holes before the compression test you may have got some carbon particles on the valve seats while cranking the engine.If it starts and runs OK i wouldnt worry too much about it,however if you feel that it is not running good then perhaps another compression test is in order. Don