[Mk2] [Turbo] low cylinder compression

[jjr]

Ok guys so my mk2 turbo has been died for a while now. cylinder compression reads 90, 30, 30, 40 psi. Its not the timing because I checked it already, everything lines up at 0 tdc. any other suggestion?

It cranks but won't turn over. I have fuel, and spark. I just don't have compression. lol. I'm trying to figure out whats happening to my compression!

[Chris]

If that is all you getting, something seriously fooked. Are you doing comp test correctly? WOT and approx five turns of engine?

[jjr]

yep 5+ turn of the engine. I'm sure I'm testing it right because thats how I test my other cars.

well I was looking at my head while the valve cover was off and notice that my valve clearance if is too little on all the valves. I don't think you can get a paper between the valve and the camshaft. (I did it right too, lube points up). Can this cost the the cylinder to lose compression because the valves are not seated correctly?

[liamc]

Get a feeler gauge to check the valve clearance with.
If the gap hasnt been maintained over the years, the valves will not be able to fully close, so you don't get compression. It'll be the exhaust valves that show this first.

Also as they arent getting to sit back into the head, they wont have the chance to dissipate the heat thats put into them, so could have a crack or hole in.

[SimonPearse]

It cranks but won't turn over.

but 'cranks', and 'turn over' mean the same thing? I assume you mean it cranks/turns over, but wont fire.
WHen you do the compression test you should :
1. ensure the king lead is disconnected
2. ensure the battery is well charged
3. have the throttle fully open (lots of people forget this)

If you have low readings on a cylinder pour a couple of ccs of engine oil in through the apropriate spark plug hole and repeat the test. If the compression is then OK it indicates a piston ring problem (the oil temporarily seals the piston/bore gap)
If it's not rings it's either valves, holed piston, crack, or badly gone gasket. (generaly burnt valve), or if the problem applies to two adjacent cylinders then its probably the head gasket.