Arcing from spark plug boot to head around spark plug!?

[Johnny]

25hp water-cooled Kohler Aegis. Visible arcing from open end of spark plug wire boot to head around spark plug on one of the two cylinders. Engine stumbles with the frequency of arcing. Replaced coil (ignition module) with attached spark plug wire and boot and spark plugs, checked connections.

Any ideas what could cause this?

Much obliged.

PS I have the factory service manual for this engine, if that would be helpful to any with this engine.

 

[FB19087]

You replaced the plug wire?

Look for carbon trails, clean them off, and use dielectric grease

 

[Dolly Llama]

is plug wire on all the way?

..L.T.A.

 

[Dolly Llama]

You replaced the plug wire?

pretty sure it's integral to the coil, Fred

..L.T.A.

 

[Johnny]

Thanks for the replies. I replaced the coil with integral plug wire and boot. Both old and new doing the same.

 

[Johnny]

You replaced the plug wire?

Look for carbon trails, clean them off, and use dielectric grease

New plug wire attached to new coil.

is plug wire on all the way?

..L.T.A.

Good idea, but its tight.

 

[FB19087]

Thanks for the replies. I replaced the coil with integral plug wire and boot. Both old and new doing the same.

Old plug look ok? Any carbon tracking?

also check grounds and plug gap

 

[Johnny]

Old plug look ok? Any carbon tracking?

also check grounds and plug gap

Old plug looked ok. Gapped new plug to .030, per service manual. Tried a wider gap, thinking .030 might be too small, but no difference.

Block is grounded. Coils mount to block.

 

[Johnny]

I have an appointment Monday with a good small-engine mechanic whose worked on mine before. But, of course, I have jobs on Monday, so I would like to get the issue resolved before Monday.

 

[KevinD]

If it only does it on one cylinder check compression for a weak cylinder.
Plug may be fouling slightly and the spark will take the path of least resistance instead of jumping the plug gap.

 

[Johnny]

If it only does it on one cylinder check compression for a weak cylinder.
Plug may be fouling slightly and the spark will take the path of least resistance instead of jumping the plug gap.

Thanks, but no plug fouling.

 

[steve_64]

Could be a timing issue. You may need to replace the square key on flywheel.

 

[Johnny]

Thanks for all your replies. The issues were incorrect gaps between the coils and the flywheel and wrong spark plugs. The new plugs had a smooth vs ribbed shaft, allowing the boots to slide up, causing arcs to the head.

Mechanic said a blown head gasket can also cause arcing, but mine seem to be good.

Smooth shaft BAD! Ribbed shaft GOOD!

 

[Cleanworks]

Thanks for all your replies. The issues were incorrect gaps between the coils and the flywheel and wrong spark plugs. The new plugs had a smooth vs ribbed shaft, allowing the boots to slide up, causing arcs to the head.

Mechanic said a blown head gasket can also cause arcing, but mine seem to be good.

Smooth shaft BAD! Ribbed shaft GOOD!

That's what my wife says too.

 

[Johnny]

That's what my wife says too.

I should have known better.