It's called a "Wet" compression test - there should not be any chance of the teaspoon of oil starting the engine - it takes *very* little oil to seal the rings during a C test!
SOP is to remove *all* spark plugs/Glow Plugs and tie the accel linkage to WOT before cranking to take a reading. Getting the engine to spin at high RPM gives the best reading - a Dry CT is also done - for the reasons mentioned (rings Vs Head problems). If someone is starting their engine they're not doing the test properly. Larry T (66 MGB, 74 911, 91 300D) www.youroil.net for Oil Analysis and Weber Parts Test Results http://members.rennlist.com/oil PORSCHE POSTERS! youroil.net 800-583-8601 Weber Carb Info http://members.rennlist.com/webercarbs ----- Original Message ----- From: "Harry Watkins" <[EMAIL PROTECTED]> To: "Mercedes Discussion List" <mercedes@okiebenz.com> Sent: Friday, May 30, 2008 1:16 AM Subject: Re: [MBZ] '87 300D saga > Jim wrote: > > "Standard compression test lore is to shoot some oil into the cylinder > and test it again, significant changes point to rings." > > I asked about doing that many years ago because I always did it with > gasser's. Someone on the old list warned that the oil could act as fuel > and > a combustion could occur. I decided to follow that advice so I still > don't > know. Is it a common practice with diesels? > > Thanks > Harry > > On Thu, May 29, 2008 at 11:03 PM, Jim Cathey <[EMAIL PROTECTED]> > wrote: > >> > Also - since the white smoke stops as it gets hot - which state is >> > "correct", or does the difference tell us something? >> >> The difference could indeed tell someone something. But perhaps >> not me. I've just heard/read that a compression test is only >> meaningful when hot. I interpret that to say that while it can >> pass when cold, 'failing' when cold isn't failure. You could >> have a gunky valve that's not sealing when cold, etc. Standard >> compression test lore is to shoot some oil into the cylinder >> and test it again, significant changes point to rings, else >> it's head gasket and/or valves at fault. >> >> I had bad white smoke on the 190D when I had the IP timed >> off by one spline. A sticky centrifugal advance mechanism >> could cause some sorts of misbehavior, though that's certainly >> a robust enough mechanism not to be particularly prone to it. >> >> -- Jim >> >> >> _______________________________________ >> http://www.okiebenz.com >> For new parts see official list sponsor: http://www.buymbparts.com/ >> For used parts email [EMAIL PROTECTED] >> >> To Unsubscribe or change delivery options go to: >> http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com >> > _______________________________________ > http://www.okiebenz.com > For new parts see official list sponsor: http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
