Electronic ignition - weak spark

[Knowledge]

Here's an interesting one. A mate calls me today with a query on electronic ignition.

The spark is weak, but when he removed the suppression plug cap and tests the end of the HT lead against the casing, it is a lovely fat spark. He has changed the CDI, HT lead, cap and plug, but always the same results. The readings from the BGM stator are healthy too.

Any thoughts?

[lammydave]

the spark on my pacemaker has always been weak looking... starts first time and pulls like a good un...

[Knowledge]

Ok, but why does this spark look good without the the cap, but weak with it?

[coaster]

Have you seen it yourself Martin? I suspect its because the spark has further to jump from the end of the lead and also there's a suppressor (resister) in the cap. Unless it'd in a shaded place I can't see much of a spark on mine either.

[xenia1]

Ok, but why does this spark look good without the the cap, but weak with it?

Its because of the energy loss due to the resister in the cap, try it without a suppressed cap and it will be different. It wont make any difference how the engine runs though as a spark is a spark, it will burn the fuel in the same way.

[johnnyXS]

mine is the same so weak that you'd think it would never work.
Its worth filing the edges of the centre and ground electrodes to a nice sharp edge as electrickery loves a nice sharp point to arc between.

[Knowledge]

Thanks guys. I am sure my mate will pick up on this advice/info when he gets up after his night shift.