Re: 96 K1500, No Compression, Cylinder #4 (Not so hard to diagnose.)

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Posted by OnBelay (76.84.26.84) on 16:51:52 09/01/09

In Reply to: Re: 96 K1500, No Compression, Cylinder #4 (Not so hard to diagnose.) posted by Igore

: What's the big deal here to diagnose? Should take about an hour.
:
: Pour some oil into the spark plug hole. Redo the compression test. If it gets better, it's the rings.
:
: Do an air blow down test (compressed air into the cylinder through the spark plug hole with the valves closed). Where the air escapes will tell a lot. Crankcase, hole in piston or rings. Coolant, cracked head or head gasket. Inlet manifold, valve related. No air escaping, push rods, lifters, rocker arms, camshaft. This isolates the problem pretty well and points to a solution.
:
: Have we become so reliant on computers that we've forgotten the old mechanic tricks? Gus Wilson would be appaled and spinning in his grave.

And even easier; pull the plug and take a look inside with a borescope. One of my customer shops has a color piece; camera lens 1/8" around, own led light on the head of a flexible shaft that displays the digital image onto the technician's laptop. Fine enough resolution you can even read the height of the piston ring ridge without taking the head off; you turn the crank and watch the valves open and close, even watch the fuel injector pulse and watch the spray pattern as it comes into the cylinder.

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Comments:	: : What's the big deal here to diagnose? Should take about an hour. : : : : Pour some oil into the spark plug hole. Redo the compression test. If it gets better, it's the rings. : : : : Do an air blow down test (compressed air into the cylinder through the spark plug hole with the valves closed). Where the air escapes will tell a lot. Crankcase, hole in piston or rings. Coolant, cracked head or head gasket. Inlet manifold, valve related. No air escaping, push rods, lifters, rocker arms, camshaft. This isolates the problem pretty well and points to a solution. : : : : Have we become so reliant on computers that we've forgotten the old mechanic tricks? Gus Wilson would be appaled and spinning in his grave. : : : And even easier; pull the plug and take a look inside with a borescope. One of my customer shops has a color piece; camera lens 1/8" around, own led light on the head of a flexible shaft that displays the digital image onto the technician's laptop. Fine enough resolution you can even read the height of the piston ring ridge without taking the head off; you turn the crank and watch the valves open and close, even watch the fuel injector pulse and watch the spray pattern as it comes into the cylinder.
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