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Ignition Wiring?

jeffkersey

Well Known Member
At my condition inspection in Feb., I decided to pull one of my impulse coupled magnetos and try a P-mag on the right. I had heard starting would be easier.
There was more room to make easier swap out on the right. Starting has not been any easier. I did not build the airplane. I am ignorant to a lot of this stuff. I am not sure if both mags were ever firing in the start position on the key switch, maybe just the left? My question. Is it ok to fire both sides during start? I would think that is the reason the builder put impulse coupling Slick Mags on both sides. Looking at some wiring diagrams online it looks like maybe there could be a jumper wire that might be causing the right mag to not send spark? If so, and that is how mine is wired, could I just clip that jumper and fire both sides and be ok?
 
You get something like 75% of the benefits with a single PMag so starting should be easier.

Not an issue anymore just curious, seems that two impulse couplers might fight each other.

Can you describe your starting procedure?

Do you have a pic of your start switch wiring?
 
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SNIP... I am not sure if both mags were ever firing in the start position on the key switch, maybe just the left? My question. Is it ok to fire both sides during start? I would think that is the reason the builder put impulse coupling Slick Mags on both sides. Looking at some wiring diagrams online it looks like maybe there could be a jumper wire that might be causing the right mag to not send spark? If so, and that is how mine is wired, could I just clip that jumper and fire both sides and be ok?

If this plane was set up with a standard configured ignition switch, I’d guess you are staring only on the left mag.

It is fine to start with an impulse coupler mag and the pMag together.

Carl
 
If you have the usual rotary ignition switch, there is a jumper 'defeat' to block one of the magnetos during start. With dual impulses, it MAY not be present.
LOOK AT Emag's installation instructions for the PMag; there is a description of what you need to know. Might also consider getting another set of eyes on it...
 
Just getting worse..

Had not really been an issue when I originally put the p-mag on in February. It has been getting harder to start. Once it starts, it runs fine. I change all the intake gaskets and hoses, as well as exhaust gaskets today. Still hard to start. I have a rebuilt impulse coupled mag on the bench I will swap with the one on the plane next.
 
Had not really been an issue when I originally put the p-mag on in February. It has been getting harder to start. Once it starts, it runs fine. I change all the intake gaskets and hoses, as well as exhaust gaskets today. Still hard to start. I have a rebuilt impulse coupled mag on the bench I will swap with the one on the plane next.

Before you change an impulse coupling, I think you should make sure that the wiring on the back of the mag switch is correct. Emag/Pmag will have the correct wiring in their directions.

On most Two-mag engines, the impulse is on the left mag. So the rotary mag switch is wired to DISABLE the right mag during start, until you release the start switch. That's what the jumper does.

Check with Emag on how the rotary switch should be set up. Much easier than changing out an impulse coupler. Your fix might be as simple as removing the jumper, but check with Emag.
 
Switch is correct...

The jumper was clipped. Still tough to start. Cleaned and gapped the plugs. That helped. I would think the lower plugs would be gunkier than the top but the opposite was actually true....
 
Jeff... Can you clarify "hard to start?".

Lots of motoring before starting? Kickback? Backfire?

Just trying to visualize the issue you're seeing. :rolleyes:
 
symptoms...

Jeff... Can you clarify "hard to start?".

Lots of motoring before starting? Kickback? Backfire?

Just trying to visualize the issue you're seeing. :rolleyes:

I bought the plane with 52 hours on everything in 2016. Once I learned my starting procedure-Full mixture, throttle wide open, 3 seconds boost pump, 1/4 throttle. When cold, it would start easily in a blade or 2. Hot starts, I would start mixture lean and throttle wide open, usually a few more blades to light.
Fast forward. 600 hours now. In the past month or so, it has been getting harder to start. Got a new battery. Did not help much. Reset timing. Still not great. Cleaning/gapping the plugs made the best improvement. Hoping that when I put the rebuilt mag back on the left it will be a non issue again.
 
Once again, can you define the "behavior" of "hard to start"? You say that you replaced the battery - was the cranking "slow"? is that the behavior you are trying to fix? If so, then your starter contactor may be getting worn (and with 600 hours, it's likely).

Does the engine spin quickly and still takes a while to catch? We need more specifics on the behavior - and if you could isolate the cranking behavior (past present) from the starting behavior (number of blades, sound, smoke, etc) that would help.

"hard to start" is not much to go on.
 
Total starter failure...

Once again, can you define the "behavior" of "hard to start"? You say that you replaced the battery - was the cranking "slow"? is that the behavior you are trying to fix? If so, then your starter contactor may be getting worn (and with 600 hours, it's likely).

Does the engine spin quickly and still takes a while to catch? We need more specifics on the behavior - and if you could isolate the cranking behavior (past present) from the starting behavior (number of blades, sound, smoke, etc) that would help.

"hard to start" is not much to go on.

Last weekend, I had a total starter failure at another airport. It was only 12 miles from home. I had a spare on the bench at home. A friend flew me home, I grabbed the new one and he dropped me off. I had it back in the air in about 40 min. The speed the new starter spun the prop was notedly faster than the one that locked up. Even with the new starter. Spinning at a decent speed. It has been tough to light. Once lit, runs smooth. THis is the 3rd starter I have put on this plane in 600 hours...
 
Have you verified the Pmag is delivering spark during the cranking event? If it is, then you probably have something else (non ignition related) going on.
 
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