Search the Community

Several weeks ago, on a 30min Encore flight, My #6 CHT went to over 600° as recorded by my JPI 711. Unfortunately, this went unnoticed in flight until engine roughness was detected on the next takeoff which was aborted. On inspection, all cylinders had compression in the 70s except #6 which was 15. Borescope inspection showed piston damage. The cylinder and piston were returned to the engine overhaul since the engine had only 200hrs since overhaul. The #6 spark plugs all had broken center electrode insulators. The overhaul shop is contributing toward the new cylinder and piston and says the classic detonation damage is caused by pre-ignition from “cross fire”, either inside the magneto or in the spark plug wire bundles. They recommend not tie-wrapping spark plug wires together. 1. Has anyone heard of this? 2. If the magneto only fires every 120°. then the only possible pre-ignition crossfire would be 120° BTDC, which if it occurred during the initial compression stroke would do it? 3. Firing order is 1-6-3-2-5-4 so the crossfire pre-ignition would have to come from #1, during #6 compression stroke. Right? thanks for any comments. Dave Ketcham, Mooney 252/Encore

Want to get your opinion on what I am seeing. Went to fly tonight and had a rough mag that I couldn't clear. The JPI indicated it was the #2 cylinder, right mag. If i remembered the cylinders orientation correctly, this should be the front left cylinder on the pilot's side. Since the JPI was indicating an issue on one mag, I pulled the lower plug. I found a very small amount of lead in it (I lean aggressively so seeing lead fouling is unusual for me). I decided to pull both plugs on this cylinder. The top one had no lead. I pulled out my trusty ohm meter and found the article Daver posted last year with the Champion plug changes that addressed the high ohm readings. I always carry a couple of new plugs with me and pulled one of them out and measured the resistance. The article said it should be between 800 and 1200 ohms. The new plug was exactly in that range (keep in mind this is a 24 year old plug). Put the ohm meter on both plugs I pulled and found them both wide open! So, obviously these plugs are toast. Right? Since I have two new ones, is there a gap spec that I need to set for them? It is clear the old plugs are getting worn. The new plug:

If you are experiencing a vibration in your mooney like I was you need to read this. One day my plane went from flying perfect to a nagging vibration. I checked everything EVEN the sparkplugs. We removed, inspected, cleaned and tested the plugs they passed; we put them back in the plane. We bore scoped the cylinders, balanced the prop, inspected the intake manifold, mags, carb, EVERYTHING. Then we took a step back and reinspected the spark plugs.....one of them was a little dirtier than the rest...we further inspected the cylinder for sticking valves....then my mechanic was regapping the plugs and BINGO! The wire had a tiny crack in it almost impossible to see with the naked eye but was noticable because the wire was "wobbling" slightly when he regapped it. New plug.......NO vibration back to running like a clock! PERFECT! I hope this message helps others that are on the brink of madeness like I was trying to solve this problem. I even had a Mooney mechanice take a ride and fly it and he said it was normal vibration.....If you notice a change in your plane don't give up or think it's in your head. These planes will speak to you when something is wrong and my plane did..The connections I failed to make during run up were: one mag would drop 100RPM vs the other only 50RPM's. This was telling me it was ignition related and I failed to notice. I was asked what happens when I did a mag check and I said it was normal...lesson learned. I hope you all benefit from this..zoom in on the attached picture of the sparkplug you will see the crack.

I was chasing down a spark plug issue (my guess is in going to find a high resistance across my top #1 that was replaced in 2014 when chasing down a Slick mag issue (thank you for your quality products Champion), but testing will tell. Anyway I wanted to test resistances across my aging leads. All leads in the harness tested with resistances of between 46-56 Ohms. I flipped the cap over on a whim and found the shielding to be frayed to the #1 bottom. The plastic appeared intact and I could wiggle the lead without any appreciable change in resistance, indicating that the conducting wire is intact. I think I am inclined to replace the leads but wanted to make sure I'm not making a mountain out of a molehill. So I wanted to gather some wisom... Thanks, Brad

During runup I noticed the mag drop to be at 200RPM on the left side. After leaning the engine at higher RPM and allowing it to run for about a minute, the drop remains between 100-125RPM. Most people I spoke to suggested that I might have had fouled plugs so I replaced them all with Tempest UREM38E (massives). After running up with new plugs, the RPM drop was normal but the engine ran rough on the same side (left). I also noticed that when full throttle is applied the RPM does not go any higher than 2500-2600. Has anyone experienced this before that might be able to shed some light as to what might be going on?