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M14P engine problem

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heaysr(at)telus.net
Guest

Posted: Sat Aug 20, 2016 10:56 am Post subject: M14P engine problem

Symptom:



Mag drop at run-up (at) 70% RPM  is 3% on Mag #1 (normal) and  5% fluctuating

to 10% on Mag #2.



Troubleshooting done to date;

- 	run engine on Mag#2 (RH mag feeding rear plugs) up to normal

cylinder head temp, 120 Deg C, shut down and measure temp of each cylinder.

No 2 cylinder found to be cold at around 45 deg C, while all others are to

approx. 100 deg C . Suspect bad spark plug

-	swap rear sparkplug plug No 2 cylinder with rear No 3. As above, run

engine on Mag#2 up to normal cylinder head temp, shut down and measure temp

of each cylinder. No 2 cylinder found to be cold at around 45 deg C, while

all others are to approx. 100 deg C . Conclusion: it is not a spark plug

problem.  Suspect HT lead from mag to spark plug.

-	remove mag #2 cover, remove rear  spark plug No 2, do a continuity

check with multi--meter on HT lead from No 2 post in distributor cap to

other end at plug connection. Circuit is continuous with .05 ohms at 200 ohm

setting. Repeat on  HT lead No 3. Same ohm reading result. Suspect HT lead

insulation or connection of lead to distributor cap..

-	remove small pointed screw at post no 2. Remove HT lead.  Looks like

screw didn't penetrate insulation. Trim off insulation. Reinstall HT lead

and reinsert pointed screw. With No 2 plug out, reconnect HT lead. Use HV

tester attached to post no 2 in distributor cap. Result: Good strong spark

visible at Plug No 2. Repeat with circuit  No 3. Again, a good strong spark.

Conclude that HT connection to post No 2 is OK and the HT lead insulation is

OK all the way to spark plug .   Suspect Mag No 2.

-	inspect all posts in distributor cap. Some have deposits. Clean to

bright metal. Look for cracks in cap. None found. Check rotor. Clean tip.

Looks OK. Check points are opening properly at No 2. Looks OK. Reassemble

everything.  As above, run engine on Mag#2 up to normal cylinder head temp,

shut down and measure temp of each cylinder. No 2 cylinder found to be cold

at around 45 deg C, while all others are to approx. 100 deg C . Same result

as above. Suspect that P lead or mag switch is wired in correctly whereby

Mag switch set at #2 shorts out No 2 and leaves Mag No 1 on rear plugs.

-   	run engine on Mag #1 up to normal cylinder head temp, shut down and

measure temp of each cylinder. No 2 cylinder found to be warm at around 100

deg C, the same as all others. Conclusion. Mag switch and P leads are wired

according to the M14P manual.  It is No 2 mag circuit to No 2 cylinder that

is the problem. Suspect we have somehow fixed the problem

-	do a full run-up with mag switch at 1+2.  Mag drop at run-up (at) 70%

RPM  is 3% on Mag #1 (normal) and  5% fluctuating to 10% on Mag #2.

Absolutely no change. Nothing fixed.



So where is the problem????



If it was the coil, why  would it not affect all cylinders. The mags are low

time (about 50 hours on them, but they are about 13 years. They sat for 11

years unused in a dry loft).



We are stumped!!



Does anyone have a diagnosis or cure. 



Royden

Yak 55M

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GeorgeCoy

Joined: 02 Dec 2010
Posts: 310

Posted: Sat Aug 20, 2016 11:15 am Post subject: M14P engine problem

I assume no arc tracking in the mag cap.  If not you probably need to

replace the #2 rear plug hi tension wire to rule it out completely. I have

not had god luck with the high tension testers.  Particularly with

intermittent changes.  I also assume you are running the original Russian

ignition. 

George



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nigel(at)yakdisplay.com
Guest

Posted: Sat Aug 20, 2016 11:17 am Post subject: M14P engine problem

 	  Quote: 	
		  From first hand experience, a coil breaking down causes all sorts of strange problems, including symptoms that appear to point to the opposite mag and even complete momentary engine stoppage even if only one coil is affected even with mags on both!


	


Shelf Age is the key. Hours do not count.



Your cheapest option and least time consuming might be try try new new coil(s)... Got mine from Gill at m14p.com. She offers core coil exchange.



Just a thought....



Regards



Nigel Willson

Tel. 07809 116676

yakdisplay.com



Sent from my iPad



 	  Quote: 	
		   On 20 Aug 2016, at 20:05, Royden Heays <heaysr(at)telus.net> wrote:

 

 

 

 Symptom:

 

 Mag drop at run-up (at) 70% RPM  is 3% on Mag #1 (normal) and  5% fluctuating

 to 10% on Mag #2.

 

 Troubleshooting done to date;

 -    run engine on Mag#2 (RH mag feeding rear plugs) up to normal

 cylinder head temp, 120 Deg C, shut down and measure temp of each cylinder.

 No 2 cylinder found to be cold at around 45 deg C, while all others are to

 approx. 100 deg C . Suspect bad spark plug

 -    swap rear sparkplug plug No 2 cylinder with rear No 3. As above, run

 engine on Mag#2 up to normal cylinder head temp, shut down and measure temp

 of each cylinder. No 2 cylinder found to be cold at around 45 deg C, while

 all others are to approx. 100 deg C . Conclusion: it is not a spark plug

 problem.  Suspect HT lead from mag to spark plug.

 -    remove mag #2 cover, remove rear  spark plug No 2, do a continuity

 check with multi--meter on HT lead from No 2 post in distributor cap to

 other end at plug connection. Circuit is continuous with .05 ohms at 200 ohm

 setting. Repeat on  HT lead No 3. Same ohm reading result. Suspect HT lead

 insulation or connection of lead to distributor cap..

 -    remove small pointed screw at post no 2. Remove HT lead.  Looks like

 screw didn't penetrate insulation. Trim off insulation. Reinstall HT lead

 and reinsert pointed screw. With No 2 plug out, reconnect HT lead. Use HV

 tester attached to post no 2 in distributor cap. Result: Good strong spark

 visible at Plug No 2. Repeat with circuit  No 3. Again, a good strong spark.

 Conclude that HT connection to post No 2 is OK and the HT lead insulation is

 OK all the way to spark plug .   Suspect Mag No 2.

 -    inspect all posts in distributor cap. Some have deposits. Clean to

 bright metal. Look for cracks in cap. None found. Check rotor. Clean tip.

 Looks OK. Check points are opening properly at No 2. Looks OK. Reassemble

 everything.  As above, run engine on Mag#2 up to normal cylinder head temp,

 shut down and measure temp of each cylinder. No 2 cylinder found to be cold

 at around 45 deg C, while all others are to approx. 100 deg C . Same result

 as above. Suspect that P lead or mag switch is wired in correctly whereby

 Mag switch set at #2 shorts out No 2 and leaves Mag No 1 on rear plugs.

 -       run engine on Mag #1 up to normal cylinder head temp, shut down and

 measure temp of each cylinder. No 2 cylinder found to be warm at around 100

 deg C, the same as all others. Conclusion. Mag switch and P leads are wired

 according to the M14P manual.  It is No 2 mag circuit to No 2 cylinder that

 is the problem. Suspect we have somehow fixed the problem

 -    do a full run-up with mag switch at 1+2.  Mag drop at run-up (at) 70%

 RPM  is 3% on Mag #1 (normal) and  5% fluctuating to 10% on Mag #2.

 Absolutely no change. Nothing fixed.

 

 So where is the problem????

 

 If it was the coil, why  would it not affect all cylinders. The mags are low

 time (about 50 hours on them, but they are about 13 years. They sat for 11

 years unused in a dry loft).

 

 We are stumped!!

 

 Does anyone have a diagnosis or cure. 

 

 Royden

 Yak 55M

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Richard.goode(at)russiana
Guest

Posted: Sat Aug 20, 2016 10:45 pm Post subject: M14P engine problem

I would be sure that it is a coil problem. These are terribly common, and

after our traditional Russian sources of coils has dried up, we were forced

to spend a lot on researching new production in Hungary which is now working

very well.



Richard Goode



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Lancer

Joined: 21 Apr 2016
Posts: 30
Location: Cairns, Australia

Posted: Sun Aug 21, 2016 5:33 pm Post subject: Re: M14P engine problem

It appears from your testing so far that you have eliminated it to #2 plug lead. The problem is that when the lead is installed inside the conduit it could be earthing and causing a loss of spark getting to the plug.



I'd replace the lead and go from there.

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