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misfiring 18T

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bvthomas(at)bigpond.com
Guest

Posted: Sun Jul 30, 2006 2:26 pm Post subject: misfiring 18T

Dear Dennis and Rodger,

 Thank you both for your input, It would appear that  this is the problem according to the symptoms which appear to be identical to your experience. 

 I will do the tests to make sure that it has gone  away.

 One thing that has me confused though,why does one  bad mag cause all this angst when the second mag is firing correctly, isn't that  the reason for two mags.? 

  

 I had a post from Michael Wikstrom in France  who had a very similar experience to mine,same symptoms again but his was caused  by fiberglass long range tanks that were dissolving and blocking the fuel filter  with glass strands.

 My plane is fitted with the same fiberglass  tanks,so I have bought aluminium tanks fron Lithuania and will fit them when it  arrives.

 Seems there is more one way to skin a  cat.

 Thanks again

 Bruce Thomas

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dstroud(at)storm.ca
Guest

Posted: Sun Jul 30, 2006 5:13 pm Post subject: misfiring 18T

Giday Bruce...I've had composite  tanks cause grief before and sloshing with POR 15

 was an easy and inexpensive fix.  Perhaps with what and where you are flying this is

 not an acceptable recommend  though.

  

 David Stroud   Ottawa, Canada

C-FDWS  Christavia  

Fairchild 51 early construction



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viperdoc(at)mindspring.co
Guest

Posted: Sun Jul 30, 2006 6:23 pm Post subject: misfiring 18T

Bruce,

 Have you checked you fuel filter screen. If your tanks are breaking down, your filter should be clogged with fiberglass if this is the case. That is a quick look that will not cost you an arm and a leg. 

 Doc

  

 



  

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mj(at)yakuk.com
Guest

Posted: Mon Jul 31, 2006 12:17 am Post subject: misfiring 18T

Morning all.



 



I would concur with mags however I would also look at 2 other factors and

especially as it appears to be on both mag positions although not uncommon

for heat soak to cause both mags to fail. (we had this on a Y50 recently 25

mins is the average. ) 



 



Lean mixture will also give these symptoms and also poor condition plugs.

Eliminate the plugs if you had just done that conversion, so Mixture.



 



Mixture - agreed filters blocking will lean the engine !! But subsequent

take off appears to be fine and that's at full fuel flow. 



 



Induction leaks. - several items here. Carb loose - inlet oil drain kit

fitted and open (common) inlet tubes loose - inlet drain kit pipes cracked.



 



Back to the mags, has any one re magnetised the armatures? We have just made

the equipment to do this and have also commissioned new coils to be wound.

The first is here to be fitted maybe this week and then bench run. If anyone

has done the magnetising please do contact me. Magnets and coils make

sparks, its no good just doing half the job!!! I.e. changing coils. 



 



Cheers, mj



Ps one winter ferry flight I had mags start to break down so opened all

gills to run the engine cool, this solved the problem till I got home.



 



Mark Jefferies for YAK UK Ltd <http://www.yakuk.com> 



Lt Gransden Airfield <http://www.yakuk.com/egmj.asp> 



Sandy, Beds



SG19 3BP - England



Conditions of <http://www.yakuk.com/cob.doc>  business



00 44 1767 651 156 ph



00 44 1767 651 157 fx



00 44 7785 538 317 mob

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dsavarese(at)elmore.rr.co
Guest

Posted: Mon Jul 31, 2006 3:50 am Post subject: misfiring 18T

The misfiring coil causes a complete purge of the fuel  charge.  That's why you get the symptom of a complete engine shut down for  a millisecond or so.

  

 I have discussed these symptoms with several M14  experts all over the world and every one of them asks "how many  minutes after takeoff before you experience the problem?"  The  consensus is 20-35 minutes on the average and you can pretty much bet  it's a bad coil. 

  

 As for fiberglass being in the fuel system, this is always  possible.  You can find out very quickly by removing both the course and  fine fuel screens and examining them for fiberglass particles.

  

 Dennis

  

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talew(at)bellsouth.net
Guest

Posted: Mon Jul 31, 2006 6:45 am Post subject: misfiring 18T

Bruce,

 Are you using an ethanol type fuel ? Ethanol will dissolve  fiberglass according to a marine industry study . Vinal ( spelling?)  ester fiberglass tanks do not seem to have this problem.  

 Terry Lewis

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Scooter

Joined: 10 Jan 2006
Posts: 155

Posted: Tue Aug 01, 2006 10:31 am Post subject: Re: misfiring 18T

Maybe someone can enlighten me but I still don't understand how the coil could be the culprit here.   Is it that the mag is firing early (purging the fuel charge) and if so wouldn't this be controlled by the points (not the coil)?  Seems like the failure mode of a coil would be a weaker spark (or no spark).

[quote="dsavarese(at)elmore.rr.co"]The misfiring coil causes a complete purge of the fuel  charge.ï¿½ That's why you get the symptom of a complete engine shut down for  a millisecond or so.

 ï¿½

 I have discussedï¿½these symptoms with severalï¿½M14  experts all over theï¿½world and every one of them asks "how many  minutesï¿½after takeoff before you experience the problem?"ï¿½ The  consensusï¿½is 20-35 minutes on the average and you can prettyï¿½much bet  it's a bad coil.ï¿½

 ï¿½

 As for fiberglass being in the fuel system, this is always  possible.ï¿½ You can find out very quickly by removing both the course and  fine fuel screens and examining them for fiberglass particles.

 ï¿½

 Dennis

 ï¿½

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bvthomas(at)bigpond.com
Guest

Posted: Tue Aug 01, 2006 2:13 pm Post subject: misfiring 18t

I want to thank everybody who replied with0 solutions to my problem,both on and off the list. 

 Obvously it can only be fuel or spark or a0 combination of both, not hard to fix.

 However at this point I have quite a gamut of0 possible variations to the fix, for the record they are. 

 1   Breaking down of the coils within the0 magnetos 

 2   High tension cross firing within the0 mag. caps

 3   Fibreglass tanks dissolving and0 cloging the fuel filters

 4   Cavitating fuel pump due to0 temperature

 5   Possible leaks in the induction0 system

  

 So by the time that I chase those rabbits down0 their borrows I should have it licked.

 Once again thanks everybody for your help and good0 advice.

 Kind regards Bruce Thomas

 VH-BVT

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viperdoc(at)mindspring.co
Guest

Posted: Tue Aug 01, 2006 5:49 pm Post subject: misfiring 18t

Good Luck.

 Doc

  

 



  

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