Having a leak down compression tester really comes in handy in these cases.
You get to listen for where the air is escaping. Out the carb? Bad intake
valve, out the exhaust pipe? Bad or stuck exhaust valve, Out the crankcase?
Bad rings or broken piston.
But if you don't have one, I'd start with: back off both valve adjusters and
stick my air hose nozzle tight into the spark plug hole and blow. If it's
coming out the exhaust, tap a bit on the top of the exhaust valve, sometimes
you can break up the carbon around the stem and get them to seat.
[mailto:email@example.com] On Behalf
Of Joe Lansing
Sent: Sunday, November 25, 2007 1:53 PM
Subject: [Spridgets] No Compression
What's the diagnosis on this condition: Compression at
about 100 PSI on 1,2,and 4, but #3 is at zero. I can
see the valve stems going up and down. There is no
unusual noise like a valve knocking on a piston. I was
not present when the failure happened, so maybe it was
noisy at one time.
Hole in the piston? broken/stuck valve?
71 MGB GT
Version: 7.5.503 / Virus Database: 269.16.6/1150 - Release Date: 11/24/2007
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