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  #1  
Old 01-09-2022, 12:20 PM
cdeggz cdeggz is offline
 
Join Date: Jun 2021
Location: Campbell, CA
Posts: 65
Default Ignition confusion

Iíve been noticing about 50% when I start my plane it starts when I give up cranking and release the key. Itís as if the act of releasing the key from start to ďbothĒ is what gets it to finally catch.

I was not sure what the issue was but was due for magneto overhaul, so I switched to dual pmags. I was expecting this to make my engine starting issues go away, but it has gotten significantly worse. I can still get it stated but almost always happens at key release after I give up. After startup everything works as expected.

Troubleshooting steps I have taken:
-Verified during cranking voltage is not dipping too low. I still see 10V on the main bus while cranking
-Started the engine with a different battery on the EI, no difference.
-probed the ignition switch (thinking maybe somehow p-leads were getting grounded in the ďstartĒ position). Everything checked out normal.

Any other ideas? It an RV-10 with IO-540-C, fuel injected.
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  #2  
Old 01-09-2022, 12:57 PM
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StephenC StephenC is offline
 
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Location: Auckland NZ
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Default

I had the same issue with my o-320. The issue turned out to be the left magneto was out of internal adjustment. This was due to wear even though the magneto only had 290 hours on it. The result of the wear and incorrect e gap was that it was trying to fire during start at 13 degrees after TDC and the engine was not catching until both mags were back online. It turned out both were out of adjustment even though they were timed correctly at 25 BTDC. I would suggest that the left mag is probably too retarded but I am not sure exactly what you can do with pmags to change that.
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  #3  
Old 01-09-2022, 01:10 PM
cdeggz cdeggz is offline
 
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I doubt this is the case since both pmags are used for starting.
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  #4  
Old 01-09-2022, 01:13 PM
OKAV8r OKAV8r is offline
 
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Just guessing but it seems like the mag switch may be the culprit.
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  #5  
Old 01-09-2022, 01:26 PM
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bjdecker bjdecker is offline
 
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Location: Georgetown, TX
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Is the jumper on the A-510-2 keyswitch between Terminal 1 and the adjacent GRD lug?
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  #6  
Old 01-09-2022, 01:30 PM
cdeggz cdeggz is offline
 
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Iíve removed the jumper that was previously on there.
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  #7  
Old 01-09-2022, 01:44 PM
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bjdecker bjdecker is offline
 
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That ring terminal on the #1 terminal looks like it's touching the GRD terminal however...

Anyhow - here's my theory - The Left Mag is starting to fail. During start, the the Right Mag is >OFF< during cranking by virtue of the key switch configuration (the jumper or ring terminal touching). Releasing the key turns the Right Mag on and there's enough spin left to fire off the engine.

Of course, that's just a theory...

edit -- what else is connected to the "P Lead" ring terminals? Is that an RPM pick up of some stripe?
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Last edited by bjdecker : 01-09-2022 at 01:58 PM. Reason: Question..
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  #8  
Old 01-09-2022, 02:05 PM
cdeggz cdeggz is offline
 
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Thanks BJ. There is clearance at the ring terminals. Thatís an illusion from the image.

I think your theory would be correct on a failing mag (as was my guess) but the issue persisted after installing the dual p-mags.

The other wires coming off the ignition are the pmag mode switch wires. Iím starting the engine in variable mode.
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  #9  
Old 01-09-2022, 02:12 PM
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bjdecker bjdecker is offline
 
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Quote:
Originally Posted by cdeggz View Post
Thanks BJ. There is clearance at the ring terminals. Thatís an illusion from the image.

I think your theory would be correct on a failing mag (as was my guess) but the issue persisted after installing the dual p-mags.

The other wires coming off the ignition are the pmag mode switch wires. Iím starting the engine in variable mode.
For grins & giggles -- disconnect the p-lead from the pMag green connector (Pin #4) on each unit and try to start it.

Also, invest in some proper ring terminals & crimper -- Look for Tyco/TE PIDG (Plastic Insulated Diamond Grip); Mouser, Digikey, others carry them.
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  #10  
Old 01-09-2022, 02:22 PM
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Mike S Mike S is offline
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Location: Dayton Airpark, NV A34
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Quote:
Originally Posted by bjdecker View Post
Also, invest in some proper ring terminals & crimper -- Look for Tyco/TE PIDG (Plastic Insulated Diamond Grip); Mouser, Digikey, others carry them.
Agree with the above----even if the current terminals are not the problem, it is good to use high quality terminals and tools.

Stein has what you need also.
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