This one has me stumped. My rider fires and runs fine only if I have a
spark plug gap!

My mower rider, an MTD, starts fine and runs if I hold the plug wire
about 1/4" from the plug. Good spark, all that. If I actually connect
it to the plug, it dies nor will it start if the plug wire is clamped
to the plug.

The only quirk here that I can think of is that I left the key in the
"on" position all night....if that makes any difference.

Bruce

The only time I've seen that happen is when the spark-plug is fouled or
bad. The act of holding it away creates a secondary gap the intensifies
the spark and lets / makes it fire in spite of too much resistance in
the plug.

Well, that was it! Geez....a fouled plug should be the first place I
should check but I didn't know the scenario I described was even
possible with a fouled plug......

Thanks Eric..... tonight we get to cut the grass before we leave now
for the Labor Day weekend!

Bruce


Eric in North TX wrote:
The only time I've seen that happen is when the spark-plug is fouled or
bad. The act of holding it away creates a secondary gap the intensifies
the spark and lets / makes it fire in spite of too much resistance in
the plug.

Eric in North TX wrote:

The only time I've seen that happen is when the spark-plug is fouled or
bad. The act of holding it away creates a secondary gap the intensifies
the spark and lets / makes it fire in spite of too much resistance in
the plug.


I've seen that too, but just to be a PIA, I'll correct your language by
saying it's too LITTLE resistance in the plug caused by fouling, not too
much.

That lowered resistance prevents the coil's secondary voltage from
building up high enough to spark across the electrodes, but as you
correctly stated, the "extra" external gap lets the voltage build up
until it breaks down, which connects much of the full secondary voltage
across the plug gap.

Change the plug, I bet you'll find that fixes the problem.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Rudeness is the weak man's imitation of strength."

I'll give you that one, makes sense to me