• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

magneto grounding

J

Jack Smith

Registered User
I have 0-360 with Bendix magnetos and a newer mag switch it L-R-start. When I leave mixture rich and shut it off with mags it sits there and fires on what seems to me on one cylinder?? Its defiantly not running on one mag its sputters but just seems like it hits on one cylinder?? I have checked grounds P leads everything seems to be in order. I am thinking the switch isn't grounded correctly?? It has to be a problem somewhere from SW to magneto?? any ideas would be appreciated thanks
 
Residual heat is firing the remaining fuel in the cylinder. It is not a magneto ignition problem. When shutting off an O-360 it is better to run it at about 1000 rpm, pull the mixture to idle cut off, then as soon as it stops firing and before it slows down, close and hold the throttle until stopped. This will give you a clean no shake shut down. With the larger engines it is better to eliminate the fuel in the engine to make it stop rather than shutting off the spark.
 
Yep, clinkers in the spark plugs are causing a glow-plug effect. Its common. If you clean the plugs it'll probably go away for a while.
 
skywagon8a said:
Residual heat is firing the remaining fuel in the cylinder. It is not a magneto ignition problem. When shutting off an O-360 it is better to run it at about 1000 rpm, pull the mixture to idle cut off, then as soon as it stops firing and before it slows down, close and hold the throttle until stopped. This will give you a clean no shake shut down. With the larger engines it is better to eliminate the fuel in the engine to make it stop rather than shutting off the spark.
Click to expand...

That must be exciting on floats coming to a tight parking spot

Glenn
 
Jack Smith said:
I have 0-360 with Bendix magnetos and a newer mag switch it L-R-start. When I leave mixture rich and shut it off with mags it sits there and fires on what seems to me on one cylinder?? Its defiantly not running on one mag its sputters but just seems like it hits on one cylinder?? I have checked grounds P leads everything seems to be in order. I am thinking the switch isn't grounded correctly?? It has to be a problem somewhere from SW to magneto?? any ideas would be appreciated thanks
Click to expand...

Is there a specific reason for shutting down with the mags instead of with the mixture cut off?

Web
 
skywagon8a said:
You can do that with the lawn mower engines which you use. ;-) The higher displacement/ compression ratio engines need some advance consideration.
Click to expand...

Never understood why aircraft engines shut down with mixture. I've been playing with all kinds of engines since I was 5. I drag raced a 68 Camaro with 12 to 1 compression and shut down with the key. Had friends with that compression and Vertex mag and they shut down with ignition. Every different aircraft (89) I've ever flown i shut shut down with mags. I think it's just a pilot ego thing to use mixture ;-)

Glenn
 
cubdriver2 said:
That must be exciting on floats coming to a tight parking spot

Glenn
Click to expand...

Lol. I had that happen. A nice fellow at a seaplane fly in was going to catch me at the dock until my engine kept dieseling. He ran for cover and left me to dock myself. I was committed with no way of stopping. It did finally shut of....(just in time)
 
On floats when I go ducking in tight places, I approach with the mixture already pulled to almost engine shutdown, throttle at idle, on the left mag only, carb heat on.... If I get in trouble I pull or push the mixture. But I always shut down my O-360 with mixture control.
 
I have never seen an 0-360 not diesel without pulling the mixture when the engine is warm/hot. I am a mixture user because I know it is going to stop the engine from turning. The only way I have found to stop the dieseling if just the key is used is to go WOT at the same time as tuning the key to the off position but not sure that is that great of a process for killing it.
 
I hand prop on floats and even if I had a mixture control I would still use mag switch to kill it because it starts better that way. I'm running most times with one blade.

Glenn
 
I had the understanding that by killing an engine with the ICO rather than by the mags. , was so that no fuel is present if you were to have a bad mag. ground and the prop. got turned. Just a chance at adverting a bad mishap.
 
True, but if your killing it with mags you would know that. No matter how you shut down prop should be treated as hot

Glenn
 
Cubdriver2, I got to ask what your secret is, and I am serious. I have done a lot of hand props and never had any engine fire on the first blade (2nd or 3rd a lot). I have also tried to use the key method without any success in hopes that it would make the next hand prop on a hot engine easier. What is the secret that makes your 89 different aircraft different from the hand full of aircraft I have tried to use your method with. These were mostly Lycoming 0-360 but I have also tried Lycoming 0-320 and 0-540.
 
My 320 will almost always start on the first blade hot, if previously killed with the mags. I was doing this for a while a few years ago, when I went on a major weight/CG bender trying to eke out all possible performance. After rebuild (no I didn't crash it) it lost weight in all the right places and I'm back to the skytec starter. For those on floats who would like to use the mags, I think a more frequent plug cleaning schedule - especially the bottom plugs - would solve most of the dieseling issues.
 
Last edited:
Mauleguy said:
Cubdriver2, I got to ask what your secret is, and I am serious. I have done a lot of hand props and never had any engine fire on the first blade (2nd or 3rd a lot). I have also tried to use the key method without any success in hopes that it would make the next hand prop on a hot engine easier. What is the secret that makes your 89 different aircraft different from the hand full of aircraft I have tried to use your method with. These were mostly Lycoming 0-360 but I have also tried Lycoming 0-320 and 0-540.
Click to expand...

Most of the stuff I've flown didn't have a mixture knob. I added it to my 11 and my 0200 18 to try to extend my fuel. I just got used to shutting down with mags. Even on the Stearman the owners standard shut down was with mags then WOT, and that would start with one or 2 blades also. The only real Lycoming time I have is behind that 225 in the Stearman and the 0320 pa12 I flew on floats. Most of the old stuff likes it juicy when cold and somewhat lean when hot?
Also if your always hand propping you get smarter as to what each engine likes for a quick start, each one is a little different. Something I do that most don't is that I never pull any blades thru after priming. I go hot on the very first pull, that's the quickest way to " discover " what each engine likes. My only 0360 time I have was a couple hrs in a 04 Top Cub on floats and that seemed happy with the mag only shutdown

Glenn
 
Last edited:
You must log in or register to reply here.

Similar threads

P
0-320 prop spinning backwards @ shutdown
Replies
22
Views
5K
cubdriver2
cubdriver2
M
mag timing
Replies
9
Views
4K
T.J.
T.J.
Lawn Dart
Proper Mag Grounding
Replies
29
Views
9K
BritishCubBloke
B
cubamigo
Backfire when leaning at 2400 RPM
Replies
29
Views
11K
beezerboy
B
WindOnHisNose
Hot start woes...
2
Replies
53
Views
20K
Jonnyo
Jonnyo
Back
Top