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Christ · 09-19-2009, 11:38 PM

No compression would be a result of open valves... but there's no way that all four cylinders would have open valves at the same time, I don't think.

Even if there was, and the belt is off the gears, you can turn the cams to the marks and then test each cylinder by cranking the engine.

An engine will only build compression if the cylinder is closed, meaning all the valves have to be closed. In your case, if the cams are disconnected, they should be aligned using the timing marks, which would put cylinder #1 at TDC on compression (regarding the valves). Being that it's not an interference engine, it's safe to crank in this state - set the cams that way, then crank the engine and check the compression number for #1 cylinder - then turn the cams 90* and do it again for cylinder number 3, then 90*, cylinder 4, then 90*, cylinder 2. (I believe the firing order is 1342, make sure you turn the cams the right direction... the "mechanic" should already know this.)

Record the compression numbers that way, then report back.

09-19-2009, 11:38 PM	#234 (permalink)
Christ Moderate your Moderation. Join Date: Nov 2008 Location: Troy, Pa. Posts: 8,919 Pasta - '96 Volkswagen Passat TDi 90 day: 45.22 mpg (US) Thanks: 1,369 Thanked 430 Times in 353 Posts	No compression would be a result of open valves... but there's no way that all four cylinders would have open valves at the same time, I don't think. Even if there was, and the belt is off the gears, you can turn the cams to the marks and then test each cylinder by cranking the engine. An engine will only build compression if the cylinder is closed, meaning all the valves have to be closed. In your case, if the cams are disconnected, they should be aligned using the timing marks, which would put cylinder #1 at TDC on compression (regarding the valves). Being that it's not an interference engine, it's safe to crank in this state - set the cams that way, then crank the engine and check the compression number for #1 cylinder - then turn the cams 90* and do it again for cylinder number 3, then 90, cylinder 4, then 90, cylinder 2. (I believe the firing order is 1342, make sure you turn the cams the right direction... the "mechanic" should already know this.) Record the compression numbers that way, then report back. __________________ "¿ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"