Re: poor mans spark plug wire tesater
In the interest of being serious, the following is a reprint of a post by Joe Reeves from another forum. The added point that the quote makes is: the quality of the spark is much more important than the presence of a spark.
" ....the ignition (spark) but apparently by simply using the spark plugs? If so, this is no test as spark will jump the very small plug gap when the plug is in open air BUT it may not jump that gap when under compression.
The spark must be a strong blue lightning like flame.... a real SNAP!
To test the spark properly, you must use a 7/16" gap at cranking speed with the spark plugs removed. You can easily make such a spark tester as follows:
Spark Tester - Home Made
(J. Reeves)
A spark tester can be made with a piece of 1x4 or 1x6, drive a couple nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere.
Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:
..........X1..........X2
.................X..(grd)
..........X3..........X4
The compression mentioned (10psi difference), low reading on top cylinder, would indiate to me that either the engine has been run with a fouled top carburetor (cylinder running lean), or the ignition being weak on that cylinder.
Let us know about the spark, with it being tested with the 7/16" gap."