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Magneto problems.... no spark

Old 10-27-2017, 01:44 PM
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Richard39
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Question Magneto problems.... no spark

I have two Fuji 50 CC Gas... Both Magneto.... I have been flying engine Number 1 and it starts up and runs ok but sputters some at Full Open Throttle... The other Fuji 50 came to me from a friend that crashed it and lost the muffler and Carb.... I put the muffler and the carb from the other Fuji on this engine and it did not hit or run... primed it still no hit or run... Using a large starter to spin the prop... My question is how do I check for spark...? I have tried to check the spark with the spark plug out and grounded to the engine but can not see a spark... have tried several gap adjustments to the magneto on this Number 2 engine.... nothing... primed it... etc... Nothing...NOW another question.... I also can NOTget a spark from the Number 1 engine still on the airplane but without muffler and carb... This engine has run , flown and idles good but I can not see a spark... So what am I doing wrong? both Engines are grounded to the Magneto...
Old 10-27-2017, 04:58 PM
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Exclamation Spark

It could have a bad spark plug or spark plug wire. Can you adjust the air gap on magneto? Your one engine if had a hard landing, could have a sheard key that holds the flywheel so timing is correct. Some mags use a ground wire to stop engine, shorting out the spark. There you go, now you got some checking to do. Captin zjohn
Old 10-27-2017, 07:42 PM
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2walla
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Set the gap on the mag with a business card. Make sure you arent grounding out the mag. Grounding the mag KILLS THE SPARK.. i would disconnect any kill switches etc to test for spark. Remember open circuit in the kill switch is run.. coosed groundes out tne mag and kills it. also try checking at night so you can see the spark better.
Old 10-28-2017, 08:05 AM
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Richard39
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Default Magneto

Thanks for the replies.... I will check all as suggested.... Thanks...
Old 10-28-2017, 09:52 AM
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Agreed on all, with an emphasis on the fact that it can be nearly impossible to see the spark in the bright daylight. Having to spin the engine over rapidly as in the case of a magneto type ignition compounds the problem. Get in the dark to check your spark, and wing that mag over fast. Mag coils DO go bad sometimes....

AV8TOR
Old 10-28-2017, 10:54 AM
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I just re-read your post where it says "both magnetos are grounded to the engine". As already mentioned, this is wrong. Remove ALL wires from the magneto except for the spark plug wire. Then ground the shell of the spark plug firmly to the engine, and then check for spark in a dark area.

I have a test lead I use to ground the spark plug shell to the engine, but a couple of good rubber bands can also handily hold the plug firmly to the engine to ground it while checking for spark.

AV8TOR

Last edited by av8tor1977; 10-28-2017 at 10:58 AM.
Old 10-28-2017, 08:22 PM
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My current test procedure for spark is to squirt some Sea Foam into the engine through the carb. Then apply the starter.

If the engine runs for a moment, you have a spark.
Old 10-29-2017, 10:35 AM
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My basic procedure on a "no start" is pull the plug and see if it is wet. If it is, I check for spark as outlined. If I get spark, I assume a flooded condition, and I clear the engine and clean or change the plug, and try it again. If it floods again, I check the carb for a stiff/stuck open regulator assembly.

If the plug is dry, I prime the engine with some fuel, (about maybe 10 drops), into either the plug hole or carb. If it starts and quits, I suspect a fuel supply issue.

Seeing spark is sometimes not the total answer either. It is relatively rare, but sometimes you can have a visual spark, but the engine won't start. In this case the spark is weak, and doesn't spark inside the engine under compression, thus, no start.

When I worked on full size aircraft, we had a tester we used for the spark plugs that put them under pressure and added spark voltage and you could see the quality of the spark for that plug.

A few years ago, I had a Chinese ignition on an engine, and that engine was nearly impossible to start cold. Once finally started, it ran fine and re-started fine. Bill from CH Ignitions advised me to go from 4.8 volts to 6 volts to the ignition. Then it started perfectly when cold. He said a weak ignition could do that and increasing the voltage would often "cure it".

AV8TOR

Last edited by av8tor1977; 10-29-2017 at 10:38 AM.
Old 10-29-2017, 01:25 PM
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Thanks to all again for the great suggestions... I have not tried to apply the suggestions yet but will Monday... One question I have is grounding the shell of the spark plug to the engine... This would be for metal shells ...? Both the Fuji's have rubber shells.... but I can fix a wire inside next to the spark plug and then ground that wire to the engine... would that be ok...? or are we talking checking the plug outside of the engine...Outside of the engine would be looking for a spark and I have also tried to run the engine on a test stand..... I believe it will spark and run Monday........ again thanks..... Richard

Originally Posted by av8tor1977 View Post
I just re-read your post where it says "both magnetos are grounded to the engine". As already mentioned, this is wrong. Remove ALL wires from the magneto except for the spark plug wire. Then ground the shell of the spark plug firmly to the engine, and then check for spark in a dark area.

I have a test lead I use to ground the spark plug shell to the engine, but a couple of good rubber bands can also handily hold the plug firmly to the engine to ground it while checking for spark.

AV8TOR
Old 10-29-2017, 05:39 PM
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Part of the problem with magneto ignitions is modern breakerless ignitions compared to the older points ignitions. Modern mag ignitions have an electronic circuit embedded within the mag coil that fires the ignition at the correct time. Often times, this circuit can fail and even though the coil windings are good, the ignition is useless and inoperative. The only fix is coil replacement and if the part is no longer available, well ..... so is the engine.

In the early days of breakerless ignitions, a small module replaced the breaker points and condenser and this could be troubleshooted, but when embedded in the coil, it either works or it doesn't creating throw away parts when it fails. Sad but that is the way things are these days.
Old 10-30-2017, 09:03 AM
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Yes, we are checking for the plug to spark outside the engine.

No, you don't want to put a wire up inside the rubber plug boot and ground it. That would kill your spark. What you want to ground is the outside metal shell of the spark plug. The part of the plug that has the hex portion for the plug socket to loosen or tighten the plug.

Good luck with it,
AV8TOR

Last edited by av8tor1977; 10-30-2017 at 09:14 AM.
Old 10-30-2017, 09:09 AM
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Originally Posted by Truckracer View Post
Part of the problem with magneto ignitions is modern breakerless ignitions compared to the older points ignitions. Modern mag ignitions have an electronic circuit embedded within the mag coil that fires the ignition at the correct time. Often times, this circuit can fail and even though the coil windings are good, the ignition is useless and inoperative. The only fix is coil replacement and if the part is no longer available, well ..... so is the engine.

In the early days of breakerless ignitions, a small module replaced the breaker points and condenser and this could be troubleshooted, but when embedded in the coil, it either works or it doesn't creating throw away parts when it fails. Sad but that is the way things are these days.
Yep. And I had an Echo magneto coil fail in an odd way. It would start and idle just fine, but wouldn't rev up. Not at all. You would think that if the advance part wasn't working that the engine would try to rev at least a little, but this one would't rev at all. I put a new mag coil on it, and it ran perfectly.

AV8TOR
Old 10-30-2017, 10:59 AM
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Richard39
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Originally Posted by av8tor1977 View Post
Yes, we are checking for the plug to spark outside the engine.

No, you don't want to put a wire up inside the rubber plug boot and ground it. That would kill your spark. What you want to ground is the outside metal shell of the spark plug. The part of the plug that has the hex portion for the plug socket to loosen or tighten the plug.

Good luck with it,
AV8TOR
Thanks to all of you ..... I have run the engine just now and it seems to be running just fine.... ran it for 3 minutes and stopped for lunch.... All is well and all of you gave me hope ... It is great to have a group of guys like each of you to help those of us that have yet to gain the knowledge of so many things in R/C... Grinning and Learning.... Richard
Old 10-31-2017, 08:31 AM
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Great news. Congrats. Glad to help.

AV8TOR

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