Magneto trouble

Rick

Rick

Well-known member
Joined
Mar 26, 2019
Messages
51
Location
Spruce Creek Fly-in Florida
I posted a question on Facebook about a magneto problem and got some interesting replies one more than the others I think may be my problem, but thought I’d post here also. Flying from Oregon to Florida I stopped at an airfield outside Palm Springs for fuel. KMMC was reporting 112°, so I’m sure the ramp was hotter. After fuel I taxied out for a run up, right mag off-normal drop, left mag off-engine quit. Turned the left back on real quick and it kept running. Mixture was leaned when I was taxiing and the DA was about 3,500” after troubleshooting back on the ramp, I could start on the left mag which has the impulse coupling but not the right mag. Pulled p lead off the right mag and started engine with no changes, after doing everything could think of I was about to close it up and try to get a right mag. It had been in the shade for about 4 hours and I decided to swap p-leads from the mags and do a run up. This time everything worked just great, having made the decision to stay the night already I swapped the the leads back and started the engine, no problems. Came out today loaded up and to problems on run up. Took off and flew 3 hours to a field outside Tucson, after landing I checked the mags and problem returned. I’m stuck in Arizona thinking I need a new mag. Does anyone have anything other to check not isolation procedures or advice? It is a Slick 4370 for reference. Thanks
 
Sounds like the P lead has an intermittent ground.

Be careful when testing with a hot mag - you can get hurt. I would remove the P lead from the dead mag, start the engine, then switch off the good mag. Keeps running? Bad P lead! But I am not recommending hot mag testing - just saying how I would do it.
 
Bob Turner said:
Sounds like the P lead has an intermittent ground.

Be careful when testing with a hot mag - you can get hurt. I would remove the P lead from the dead mag, start the engine, then switch off the good mag. Keeps running? Bad P lead! But I am not recommending hot mag testing - just saying how I would do it.
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That was one of the things I tried, took of the P lead off the right mag to isolate the switch. Didn’t change anything. Checked the connections before removing any wires. Seems like once it cooled down it was fine. And I’d bet if I go start it in the morning it would be just fine. But since I’m in Tucson and still have to make it to Florida I’d like to trouble shoot it to be certain. But unfortunately in the position I’m in I may have to buy a new one and hope for the best.
 
sounds like bad coil to me breaks down when hot, if you ohm it out it will need to be checked cold and hot. Good luck.
 
That’s what I was thinking, but I’ve never had any first hand experience. Being that I’m moving cross country I’m leaning towards just replacing the mag, but I hate throwing parts at a problem. As far as I can think of there is nothing else I can check. The A&P out here said he could start in the morning checking all the plugs. What am I missing?
 
I might suggest replacing the impulse mag with a sure fly Electronic ignition and then take the coil From that Mag put it into the other one, you’ll really like the electronic ignition much better. This way you improve your overall system and get rid of the 500 hour inspection.
 
Bruce said:
I might suggest replacing the impulse mag with a sure fly Electronic ignition and then take the coil From that Mag put it into the other one, you’ll really like the electronic ignition much better. This way you improve your overall system and get rid of the 500 hour inspection.
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I like that idea.
 
Hiperbiper said:
Sounds like a bad condenser to me...

Did you have any luck getting a mag installed?
Chris
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Hey all thanks for the advice input. Got a new mag up in Phoenix and installed it this afternoon. Took off about 1630 in the nice 110° Temps from Marana to Las Cruces and did a mag check on landing and no issues. Now to dodge thunderstorms from here to Daytona Beach and I’ll be good!
 
Bruce said:
I might suggest replacing the impulse mag with a sure fly Electronic ignition and then take the coil From that Mag put it into the other one, you’ll really like the electronic ignition much better. This way you improve your overall system and get rid of the 500 hour inspection.
Click to expand...
I think this a a decent idea, the place I picked up the mag from said good things about the Surefly. The shop that helped me out with the mag install was actually taking a fairly new one off a C-172, pilots said it started running very rough on a cross country flight. Not sure how long they have been around, I need to do some more research but seems like a good idea to replace that left mag if the solid state system holds up.
 
I have a pa28-161 after engine overhaul had all kinds of starting problems (I’m the A&P) and thought it was a primer issue, then on way to Air Venture 2019 (so sad no 2020) landed at BBU in wis. And no start left plane there went to air show On way back spent 2 hours getting it started as soon as I arrived home I installed new Surefly one to two blades and off we go runs smoother starts great hot great, wish I would have done this at overhaul. The mag I removed had less than 400 hrs and at overhaul I put new points in it ($100 bucks or so rest looked good)

glad your on your way safe flying if I have any issue with my 7ECA mag it’s gone.
 
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