[AT] Compression values and range

Dean Vinson dean at vinsonfarm.net
Fri Sep 29 04:27:14 PDT 2006


Mike Sloane wrote:

> Based on everything I have read about this tractor's problems, I would 
> have to say that it either has very low compression or weak spark under 
> compression. I had a Ford N that was very hard starting, and it turned 
> out that the rings were broken on two of the pistons. It would run, once 
> I got it started, but a compression check showed two cylinders with about
> 30 pounds compression. Burned valves can also cause poor compression.

Mike, I do have significantly lower compression in two cylinders than in the
other two.  #1 and 2 are at 115 and 118 psi respectively, but #3 and #4 are
at 90 and 105.  90 seems mighty low compared to 118 but it's nothing like
the 30 in your example.

What do those numbers tell me?  Is 90 bad?  Or is the fact that it's
different from the other ones bad?  I assume the lower numbers mean worn
rings but probably not broken ones, and the tractor ought to run fine for
what little work I'm going to ask of it.

Dean Vinson
Dayton, Ohio
www.vinsonfarm.net






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