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  #1  
Old 05-02-2009, 06:29 PM
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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.....

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Old 05-02-2009, 06:34 PM
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i was under the impression that anything above 320 was alright, not 220
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Old 05-02-2009, 07:01 PM
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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.
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Old 05-02-2009, 07:12 PM
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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.
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  #5  
Old 05-02-2009, 07:18 PM
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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.
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Old 05-02-2009, 07:22 PM
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what fitting did you use
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  #7  
Old 05-02-2009, 07:44 PM
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Quote:
Originally Posted by kerry View Post
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 agree. My engine is 320-350 and can start at -20*f with only glowplugs.
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Old 05-02-2009, 08:52 PM
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Fitting...

Quote:
Originally Posted by 1985300d View Post
what fitting did you use
Used a Compression check tool for diesels from Harbor Freight (around $35)... it has a number of fittings that you can choose from...
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Old 05-02-2009, 09:01 PM
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Quote:
Originally Posted by MercFan View Post
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.
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  #10  
Old 05-02-2009, 10:56 PM
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My book says 220 cold minimum.
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  #11  
Old 05-03-2009, 08:41 AM
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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.
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  #12  
Old 05-03-2009, 01:07 PM
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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.
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Old 05-03-2009, 05:13 PM
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Originally Posted by 78240D View Post
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.
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  #14  
Old 05-03-2009, 07:27 PM
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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?
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  #15  
Old 05-03-2009, 08:36 PM
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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

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