Luther, If we break down the problem a bit, first assume head and head gasket is OK. So compression can be low because of:
1) poor seating valves 2) bad sealing of piston rings 3) Valve timing 4) air intake (valve duration and air flow) Now if we assume vavle seats and piston rings are good then poor compression could be: Camshaft timing is ruled out since all cylinders are not low. Carboned intake not letting air come into cylinder is a possibility but low likely hood. Then there is also worn intake cam lobes not opening intake valves fully. Note worn exhaust valve lobs will usually cause high compression readings, while worn intake causes lower readings (no air coming in nothing to compress). As I recall the first movement of compression gauge is a good indication of rings. That is the first time the compression gauge's needle moves it should be 75%(as I recall) of the maximum reading if not then you usually have worn rings or cylinder walls. As far as oil consumption I would check turbo first, if the turbo seals are gone it will use oil and may only use oil during hard acceleration. Also if turbo oil seals are bad this will increase intake carbon build up. I know Marshall says intake carbon causing problem is rare. Also if you have a cylinder or two which have had a bad injector then the compression will be lower on those cylinders due to rings not seating. That is the pressure in the cylinder help rings seal to cylinder walls. Thus carbon and other build up can prevent the sealing. My recommendation is to run some diesel purge and do a few lead foot tune ups, then check compression. Note that my worn out OM617 has 250PSI on one cylinder which causes a miss at idle, and car to be a bit slow. It uses/leaks about 2 quarts in 5k miles. I have tried and tried to blow the thing up, but at last it may drive to the bone yard. Trampas -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Luther Gulseth Sent: Monday, March 27, 2006 9:38 AM To: [EMAIL PROTECTED] Subject: Re: [MBZ] '82 300CD excessive oil usage-update Would a cylinder be able to produce 300psi compression if it had broken rings/cracked pistons/scored cylinder walls??? Remember my compression figures were 300, 300, 380, 335, 360 and the injectors that were coated with carbon the most had the lowest compression. #3 injector was the cleanest, yet dirtier than my 75kmi injectors. Luther ~with that much oil usage, you either have a bad bad leak, broken rings, ~cracked pistons, scored cylinder walls ~ ~Luther Gulseth wrote: ~> With a nearly dry undercarriage, where else could it be going? Not rings, ~ ~> valve guides, or seals. Could have been valve cover baffle, and might be ~> turbo seals. Is there any other place that can loose oil internally? ~> ~> On Sun, 26 Mar 2006 20:05:32 -0600, Marshall Booth <[EMAIL PROTECTED]> ~> wrote: -- Luther KB5QHU Alma, Ark '83 300SD (231,xxx kmi) '82 300CD (159,222 kmi) '82 300D (74,000 kmi) needs MAJOR work _______________________________________ http://www.striplin.net 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://striplin.net/mailman/listinfo/mercedes_striplin.net
