I assume you're saying that, pertaining to the "stop" button, it has continuity ONLY when it is pushed in?
Regardless, remove the spark plugs when checking for spark which should jump a 7/16" air gap with a strong blue lightning like flame... a real SNAP! Note that check spark with the spark plugs is a waste of time.
Spark testers can be bought at any auto parts store... ORE if you have the time, build the following.
(Spark Tester - Home Made)
(J. Reeves)
Most auto part stores have "air gap" spark testers... OR..........
You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:
A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing 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. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.
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 wire that leads from the power-pack to that stop button... disconnect it temporarily. If still no spark, are you absolutely sure that the replaced power-pack is okay? Yes, even new ones have been know to fail sitting on the shelf!
Check the readings of the stator as per your service manual.