Ever had a bad set of plugs?

[rdv]

Hi Folks,

I screwed in a new set of Unison plugs the other day. High time IO-360, so I thought I should be able to burn-off the remaining couple hundred hours of TBO with them. First issue, one of the plugs was totaly dead (nice to have an analyzer to zero in on bad cylinder!). No prob. New plug, away we go. I changed the oil over to 15w50, buttoned it up and filed a plan for a local trip. On run-up, one of the plugs in #3 appeared dead. I leaned it out @ 1800 or so and it cleared up. Great. Im thinking it got fouled when I was warmimg engine for oil change. Now im climbing out through 3000', and I notice #3 egt is rising. Switch over to left mag, sure enough, its now a IO-270. I decided to fly around the strip and see if more aggressive leaning clears the plug. The next fifteen minuted, EGT would go up and down every few minutes. Each time it rose, I confirmed bad plug. When it came down, mag check showed good plug. Then it decided to stay on-line, and the rest of the flight went as normal. Wierd hey? I guess I'll fly with it again to see if it is finally clear, but something seems strange to this low-time driver.

Ryan

[carusoam]

Ryan,

Things to check when changing plugs.

[1] New crush washers.

[2] Torque wrench and proper torque value.

[3] Clean connection to ignition wires, Age of ignitions wires, might consider changing these out also.

[4] Time since O/H on magnetos.  I believe 500 hrs is the usual recommendation.  If you are up over 1,000 hrs since O/H.....

[5] Are these different plugs than what was in there before or are they identical replacements?

Best regards,

-a-

[acronut]

Quote: rdv

Hi Folks,

I screwed in a new set of Unison plugs the other day. High time IO-360, so I thought I should be able to burn-off the remaining couple hundred hours of TBO with them. First issue, one of the plugs was totaly dead (nice to have an analyzer to zero in on bad cylinder!). No prob. New plug, away we go. I changed the oil over to 15w50, buttoned it up and filed a plan for a local trip. On run-up, one of the plugs in #3 appeared dead. I leaned it out @ 1800 or so and it cleared up. Great. Im thinking it got fouled when I was warmimg engine for oil change. Now im climbing out through 3000', and I notice #3 egt is rising. Switch over to left mag, sure enough, its now a IO-270. I decided to fly around the strip and see if more aggressive leaning clears the plug. The next fifteen minuted, EGT would go up and down every few minutes. Each time it rose, I confirmed bad plug. When it came down, mag check showed good plug. Then it decided to stay on-line, and the rest of the flight went as normal. Wierd hey? I guess I'll fly with it again to see if it is finally clear, but something seems strange to this low-time driver.

Ryan

[rdv]

I cleaned the springs on the ignition wire ends with sandpaper. They appeared to be coated in a light film of rust. Engine starts and runs better than ever. 

 

Thanks for your thoughts,

 

Ryan

[Capt_CrashN_Burn]

Quote: rdv

I cleaned the springs on the ignition wire ends with sandpaper. They appeared to be coated in a light film of rust. Engine starts and runs better than ever. 

 

Thanks for your thoughts,

 

Ryan

[thinwing]

If I understand your post,sounds like problems started as soon as you changed plugs...Did you gap them correctly...a little to wide and they put a lot more strain on the mags...to narrow and they cause hard starting and easy fowling.The end springs on a unison type high tension lead should be clean metal.They are designed with a tapered plug that not only pressurizes plug body as you tighten cap but keep out water,so there shouldnt be any rust.Burned springs are a sign of arcing...failed resistive section of plug.Good luck..kpc

[Kwixdraw]

Always keep in mind that plugs are fairly fragile and as the old saying goes,"If you drop it once, drop it twice...(2nd time in the trash)".  You can never tell if someone handled them a bit too roughly before you got them.  Also Champion recommends that if you ever close the gap too much you should toss the plug rather than try to open the gap back up. All the other posts have good advice in them too.

[rc454]

Check out www.plugguy.com - we had great results