Inline spark tester

[F.O.R.C.E.]

Hi all

I just got a adjustable inline spark tester, but having surface gap plugs I,m not sure how wide to set the gap. The book said to set it to what the plug gap calls for, I set it to almost 1/4 in. and still had spark jump across.

Just curious on what the text book setting would be.
Thanks

 

[tashasdaddy]

Re: Inline spark tester

tester on outboard, 1/2 inch, you will get better performance and less fouling out of the plugs, to go to the comparable gapped plug.

 

[F.O.R.C.E.]

Re: Inline spark tester

tester on outboard, 1/2 inch, you will get better performance and less fouling out of the plugs, to go to the comparable gapped plug.

Wow a 1/2 in. I thought I was doing good with 1/4in-- will test again

By the way -- Whats the least it could be ,to be acceptable?

 

[Frank Acampora]

Re: Inline spark tester

It is not a question of most or least. Your electronic ignition generates about 60,000 volts versus the approximately 10,000 volts for old fashioned battery, coil, and points. This is sufficient to jump a 1/2 inch gap. A poorly operating electronic ignition may still generate enough voltage to jump the aopproximately .060 gap of the surface gap plugs while testing, but a low voltage spark will not adequately fire during operating conditions. (It takes more voltage to jump a gap under compression)

If you have a Force engine, do not be persuaded to use a bent electrode plug like OMC does. These can melt holes in the piston heads. Yeah, you may get slightly better idle performance but is it worth the gamble?

SO: test at 1/2 inch gap. A bright blue spark is what you are looking for.

 

[rodbolt]

Re: Inline spark tester

I use 7 sixteenths most any modern ADI ign system and most all TCI systems will do it and if not you can find the weakspot.
the F250 yamaha will jump over a 3 quarter inch gap.
on the 60 KV thing, some are capeable of generating that much but in reality typically run 6 to 10 KV.
some systems like the F250 that use a coil on plug setup also use a zener diode that WONT break until secondary spark voltage goes above 32 Kv.