Mower usually starts one or two pulls. Compression feels good, getting fuel because spark plug wet when I pull it. Plug measures 19k ohm tip to electrode, about 3m ohm tip to threads. Should be infinite correct? Also coil reads 5k ohms plug wire to coil frame, 5k ohms plug wire to kill tab, and 0.6 ohms kill tab to frame. So do I have a bad plug, bad coil or both? Thanks in advance.
ILENGINE
Lawn Royalty
- Joined
- May 6, 2010
- Threads
- 44
- Messages
- 10,997
Testing of the spark plug and coil without special testing equipment is meaningless. Try a known good plug and crank the engine and check for spark. If no spark then remove the starter housing and disconnect the wire to the coil. and then crank the engine if no spark then bad coil. If spark, then the kill wire is being shorted to ground for some reason.
Tiger Small Engine
Lawn Addict
- Joined
- Dec 7, 2022
- Threads
- 3
- Messages
- 1,298
Also, make sure engine brake/kill lever cable is pulling the switch far enough to allow and kill spark. Put a clamp, pliers, channel lock on it to test if needed.
When you remove the starter shou as IL suggests, you will be able to see if the brake bail is pulling the brake pad away from the flywheel. Only backyard mechanics rely on ohm meters to test spark plugs.
sgkent
Lawn Addict
- Joined
- Sep 27, 2017
- Threads
- 35
- Messages
- 1,783
I do not know specific resistance on a mower but resistance type ignition systems in general are around 4,000 to 10,000 ohms for their ENTIRE length including the resistance wire and plug. 19K sounds like a bad plug. That said, as plugs run the electrode can glaze so it can be hard to get a good reading on it. I would replace it or measure a known good one of the same type.