Spark on tester but not on plug

[Pioneer]

Had this happen to a saw I just picked up, it would give me an indication on the neon tester but not with a spark plug. I checked the kill switch by disconnecting it, no luck there. Then I checked the coil gap, seemed excessive. I adjusted it down to where it should be with a shim and got a nice fat spark. So the tester was actually indicating a weak spark where the plug would give you none at all, in this way the tester actually helped with the diagnostic.

 

[Bob Hedgecutter]

If you know the plug you are suspecting is 100% good- like good strong spark in another device- then yes.

 

[stihltech]

Neon testers don't impress me. I have had them show spark but not start. I like a tester that is basically a plug without the side electrode. If it sparks that, ignition output is OK.
Unless it is an L77 plug. Get a real plug first.

 

[sean donato]

Plenty of good cheap gap type spark tester out there. I favor my opama brand but you can get cheap version for under $15.00.

 

[Mad Professor]

Have somebody hold the plug and pull the recoil.

 

[Okie]

neon spark testers suck big air. They will lie to you about spark being ok.

I do not use neon ignition testers.

I suspect if you had to shim something to get a good fat spark something is still not completely correct.

 

[SteveSr]

Neon testers don't impress me. I have had them show spark but not start. I like a tester that is basically a plug without the side electrode. If it sparks that, ignition output is OK.
Unless it is an L77 plug. Get a real plug first.

It only takes about 80V to flash a NE-2 neon bulb. Spark tester result depend on exactly how the bulb is wired or if ti is just capacitively coupled.