captinjohn

I did a lot of running on a small spark engine today. I was using a electronic ignition on it with magnetic pick-up. The engine started to miss once in a while on Idle. Then the engine would quit when on idle for no apparent reason. I thought I could hear a snap of spark once in a while. Come to find out...the spark would jump up tp 3/8 plus to the engine instead of jumping the small .025 gap at spark plug electrods. I cleaned the insulater part of spark plug and made sure the boot was super clean. That cured the miss and the engine no longer stopped for no reason on idle. Be sure and check all this...it can be a real problem. Cap,tn

tkg

My Feedback: (1)

Can you say Silicone Dielectric Grease???

av8tor1977

My Feedback: (6)

Yeah, I've seen this kind of problem before, and the plug can look pretty clean and still "leak away" current and not have a good spark. When we used to clean and gap plugs for airplane engines, (full size), we had a machine that put the plug under high pressure and supplied current for a spark. It had a window where you could view the spark while you raised the pressure to verify proper operation in a somewhat simulated "real" environment.

I just fixed a guy's Volkswagen powered dune buggy. It had a horrible misfire even though the plugs looked good. All the rest of the ignition system checked out, so I put new plugs in it and it ran perfectly. This situation is somewhat less problematic with high energy capacitive discharge ignition systems, but it can still happen.

AV8TOR

captinjohn

TKG: I was thinking of a spray that may work like Dielecltric silicone grease. Which works best? What brand do you use? Thanks Capt,n[X(]

tkg

My Feedback: (1)

No spray use the real stuff. Get it at any auto parts place. Most of the kids working the counter call it spark plug boot grease.
You DONT want spark plug anti-seaze

captinjohn

What spark plug in the 1/4X32 size seems to be the best brand. I plan to use it in a Hit & Miss Model engine. Thanks Capt,n