URQ quirqiness Compression testing

Lyle lws at o-o.yi.org
Sun Apr 30 16:10:25 EDT 2006

My guess is that if the compression gauge doesn't even bounce, there must be

(a) an awfully big hole in the cylinder or piston
(b) all the valves are absent
(c) a thrown rod
(d) or the gauge is broken.

If the intake valves were stuck open, you'd be backfiring like crazy.
If the exhaust valves were stuck open, you'd be dumping raw fuel into the
exhaust, which you could surely smell, and would probably ignite in the
catalytic converter.  Though that's probably happening anyway.

If I had to bet, I'd bet (d), and that the real problem is ignition, not
compression. a,b, and c aren't supposed to happen when you're "just driving

Once upon a time, I had a similar experience with a Toyota - driving along
smooth and all of a sudden it just *quit*. When I tried to restart it, it
just spun, sounding like all the spark plugs had been pulled -- just as if
there was no compression at all. I had already been told by a shady stealer
that I had a blown head gasket, so I was convinced then that he was right.
I ripped it all apart and the head gasket was fine - no trace of leakage.
With no idea what was wrong, I put it back together and started it up and it
ran like a top.  Beats me.

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