The Ford Barn - View Single Post - #4 cylinder misfiring. Spark good. Compression 53 psi

100IH · 11-30-2016, 01:30 PM

When you suspect that there is a valve sticking, after everything is back together,
you can test compression with the schrader removed from the threaded end of the hose. The needle will jump up and then drop to zero. Works very much like a vacuum gage. This is more to find an intermittent issue - sticky valve or weak valve spring. Can do this by a long starter crank and/or by running engine for a short period. Similar to using a scope - watching in real time.

11-30-2016, 01:30 PM	#13
100IH Senior Member Join Date: Dec 2011 Location: SW Idaho Posts: 970	Re: #4 cylinder misfiring. Spark good. Compression 53 psi When you suspect that there is a valve sticking, after everything is back together, you can test compression with the schrader removed from the threaded end of the hose. The needle will jump up and then drop to zero. Works very much like a vacuum gage. This is more to find an intermittent issue - sticky valve or weak valve spring. Can do this by a long starter crank and/or by running engine for a short period. Similar to using a scope - watching in real time.