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08-17-2008, 10:32 AM
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Join Date: Apr 2006
Location: Sedro Wooley, WA
Posts: 147
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Cooking P Mags
George,
Good points about electronic reliability. That has been my experience in the past as well. I only mentioned the heat as a possible problem because I wanted to share all the facts. I really don't think that is the problem but we will see.
Bill,
I don't think the ground wires are a problem but who knows? Brad and the crew will have the mags Monday afternoon and the facts will be shared with all.
If I did not mention it before, I do have the cooling blast tubes installed and the wiring is just like Emagair suggests. Brad asked if the oil temperature readings have been high, I suppose to get a sense if cooling was an issue, because some folks have been having a problem with not getting enough airflow through the cowled area due to exit air restrictions. On my RV that doesn't seem to be a problem, I have been seeing oil temperatures in the 180 to 190 degree range, and yes I did put the sender in boiling water once to see if it read close to 212. I know that is a little cool but that is another issue.
I think the problem is electrical (electronic) in nature and is internal to the Pmag but that is just a guess. We will see and I will post the results.
Where I live I have to have reliability. When I fly to Valdez, only 100 miles straight away, it is across 2 mountain ranges Three ice fields, numerous glaciers and Prince William Sound, not one good landing area anywhere inbetween unless I follow the road, then it is 345 miles or so to Valdez.
Mike Ice
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08-17-2008, 12:53 PM
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Join Date: Jan 2005
Location: Chandler, AZ
Posts: 2,904
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Shoot!!
Hi Mike,
I was hoping you'd find something. There is clearly some issue that needs to be rectified. At least Brad and crew turn them around quickly.
Let us know what they find. There hasn't been a report of a problem in a while.
Quote:
Originally Posted by Mike Ice
Darwin,
I went to the airport and pulled on the wires of the P-Mag hoping to find what you mentioned but no joy. The wires were secure and the fixture was tight. I then pulled the plugs and they were all good. I centered the engine on TDC and both mags had bright green lights so they were in time.
At that point I pulled both the P mag and the E mag and put them in a box and they are on their way to Azle Texas.
By the middle of next week I should know what went wrong. Or at least I hope that they find something wrong. If they don't find something then I am really going to be troubled.
Mike Ice
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__________________
Darwin N. Barrie
Chandler AZ
www.JDair.com
RV-7 N717EE-Flying (Sold)
RV-7 N717AZ Flying, in paint
EMS Bell 407,
Eurocopter 350 A-Star Driver
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08-18-2008, 01:10 PM
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Join Date: Apr 2006
Location: Sedro Wooley, WA
Posts: 147
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P mag mystery
Darwin, Bill and others,
The P mag was at Emagair today and this is what they found:
Mike:
We were unable to recreate an anomaly on our work bench, so we went ahead and replaced the circuit board (all the electronics). Circuit boards are not cheap ($350 each), so carrying around an extra board is something you could certainly do, but I don't think it represent good value. The units will ship later today.
Kindest Regards,
So now what? I guess I will get it back, put it on and give it another try. I guess i will stick close to the airports for awhile. Bummer! Summer is so darned short here.
Oh well.
Mike Ice
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08-18-2008, 01:21 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Mike,
That is very odd. It sounds like you didn't over temp the thing, which is good.
Time to check your plug wires and make sure they aren't shorting out any place. Also, verify the other wires.
Hey, what size wire did you use to power them? I ask because the early manaul called for 20 AWG wire but later they found out that wasn't large enough and asked everyone to upgrade the power and ground lines to 18 AWG.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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08-18-2008, 09:25 PM
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Join Date: Apr 2006
Location: Sedro Wooley, WA
Posts: 147
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Pmag mystery
Bill,
When I get the mags back I will install them and hope for positive results.
I did use 18 awg wire for all connections. I will check the plug wires. I will check eveything at least twice.
I still want these mags to work and will do what I can to "make it so".
Mike Ice
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08-18-2008, 11:57 PM
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Join Date: Aug 2005
Location: N. Yorkshire, England
Posts: 1,050
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Mike, are you running aircraft or auto plugs. If you said, I missed it.
The reason I ask is that when I made up my auto plug harness there were strict instructions about not 'nicking' the inner core. I do not know what the symptoms would be if you did, but its just a thought since the heat soak idea appears to be wrong.
In the assembly instructions there was a clear statement of how to test each lead for resistance, to check none were nicked. I wonder if that is a possibility?
Hope something shows up soon for you.
Good luck,
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08-19-2008, 08:34 AM
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Join Date: Jan 2005
Location: Blue Ridge, Georgia
Posts: 247
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Plugs?
Mike, while you are at it, go ahead and pull the plugs for the affected P-mag and clean/gap again. Who knows at this point?
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08-19-2008, 10:44 AM
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Join Date: Apr 2006
Location: Sedro Wooley, WA
Posts: 147
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More P mag reflections
Steve,
Yes. I am using Auto (NGK) spark plugs. I was very careful with the assembly of the plug wires but who knows. I will likely get the mags back today and when i put them back on I will measure the resistance in all the wires. The wires are spiral wound graphite and have a certain OHM's per foot so I guess i will just measure and do the math.
Brett,
I pulled the plugs and they looked good but I will reset the gap when I put them back in or i will just put new ones in at that time.
Also when I reinstall the mags I will switch mags from right to left. I have one emag and one pmag so if the problem reoccurs and changes sides then I will have a new place to strat looking.
I had a long talk with Brad at emagair this morning and he was as usual very helpful and we talked about trouble shooting.
Mike Ice
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08-24-2008, 09:06 AM
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Join Date: Apr 2006
Location: Sedro Wooley, WA
Posts: 147
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Another p mag update
Here is the latest,
I finally got out to the airport and reinstalled the mags. I checked all the wiring again, it was ok. I pulled,cleaned, regapped and replaced a few spark plugs. I timed the mags using the blow in the tube method.
On the test flight the engine started and ran fine. The problem seems to have gone away and I hope it stays away. Now I just need to build confidence in the mags by a long period of time with no problems.
Today I am going to change the position of the grounds to the mags at Bill R's suggestion. He brought up an interesting thought and it makes sense to me. I have the mags grounded to the common firewall ground and he suggested that this presents a single failure point if the engine ground strap failed. So today I will ground the mags to the engine case.
As I wrote that I wondered if doing so would be wise. What happend if the ground strap to the engine fails and I have the mags grounded to the engine only?
Hmm! Maybe the mags should be grounded at both the engine and the firewall.
Mike ice
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08-24-2008, 11:34 AM
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Join Date: Aug 2005
Location: N. Yorkshire, England
Posts: 1,050
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Mike, you should ground the P-mags to the engine case for two reasons.
1) The install instructions say to do it that way. See p.4.
2) You will have the lowest resistance circuit, and therefore the P-mags will finally quit when self generating at the lowest possible rpm.
Yes, if your engine to firewall ground fails you will be running only on the self generation capability, but at least you will know the ground strap has failed because you wont be able to start the engine. I think the answer here is make a really good ground strap! Examine it regularly. To my mind it is about the most important wire on the aircraft.
I have actually grounded my p-mags to two different places on the engine to make them as independent as possible. A bit of an overkill, but hardly difficult.
I hope all goes well for you now.
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