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Tractor Talk Discussion Forum

Magneto fires/Engine won't!

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loveshisallis

02-07-2008 17:03:46




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I have a FM J4B3 magneto with good spark on all fours. Problem is , when I put in on the engine, it refuses to fire. I know that the engine is good, and the timing, as when I put the factory distributor on, it fires up immediately!
Sooooo oooo, what is the problem with the magneto? I check the internal timing, seems good. I welcome ideas, suggestions on how to get the magneto right.




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Old Roy agiin

02-09-2008 19:43:01




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
ON THE SIDE OF THE MAG, THE TERMINAL FOR MANUAL SHUT OFF IS SHOWING A LOT OF PAINT ON IT. I ALSO AGREE ABOUT PAINT ON PLUGS IT SHOULD DEFINATELY RUN BETTER EVEN WITH DISTRIBUTER I WOULD ALSO LEAVE CAP BLACK,AS IT WOULD ISOLILATE ANY ELECTRICAL FLOW. ALSO REPLACE THAT SOFT PLUG BEFORE YOU START HAVING TROUBLE WITH THAT TO.



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Old Roy

02-09-2008 19:38:15




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
ON THE SIDE OF THE MAG, THE TERMINAL FOR MANUAL SHUT OFF IS SHOWING A LOT OF PAINT ON IT. I ALSO AGREE ABOUT PAINT ON PLUGS IT SHOULD DEFINATELY RUN BETTER EVEN WITH DISTRIBUTER I WOULD ALSO LEAVE CAP BLACK,AS IT WOULD ISOLILATE ANY ELECTRICAL FLOW. ALSO REPLACE THAT SOFT PLUG BEFORE YOU START HAVING TROUBLE WITH THAT TO.



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Old ROY

02-09-2008 19:36:45




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
ON THE SIDE OF THE MAG, THE TERMINAL FOR MANUAL SHUT OFF IS SHOWING A LOT OF PAINT ON IT. I ALSO AGREE ABOUT PAINT ON PLUGS IT SHOULD DEFINATELY RUN BETTER EVEN WITH DISTRIBUTER I WOULD ALSO LEAVE CAP BLACK,AS IT WOULD ISOLILATE ANY ELECTRICAL FLOW. ALSO REPLACE THAT SOFT PLUG BEFORE YOU START HAVING TROUBLE WITH THAT TO.



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Old Roy

02-08-2008 15:06:36




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
paint on the kill switch shorting out



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36 coupe

02-08-2008 02:36:57




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
Make sure the spark will jump the plugs gap.Carbon fouled plugs will let the spark run up the nose of the insulator.The cylinder wont fire when this happens.



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gene bender

02-07-2008 23:21:29




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
Does the rotor line up with the tower when it impulses.



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David Maddux

02-07-2008 19:56:56




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
Make sure that your valves are operating correctly. Might pay to do a compression check.



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loveshisallis

02-07-2008 19:16:37




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
I notice that the impulse does snap at "CENTER" on the flywheel, and yes, I check to make SURE that this is on the compression stroke.Weh the impulse does SNAP , I do get a good spark and then look and find CENTER is lined up through the hole in the bell housing.

I have copper wires on the mag. I did notice that I have R45 AC plugs, as I couldn;t find 45's.Plugs are gapped at .030. Can anyone recommend, specifically, what kind, brank of plugs to get for this mag ?
I am going to look MORE and try to get these though, from comments in this thread. I appreciate all the help, guys!

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DickL

02-07-2008 19:34:50




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 UP THRU ??? in reply to loveshisallis, 02-07-2008 19:16:37  
You don't mean up do you?? It aint a WD it is a B and it is (in) thru on the left side between the two 5/8 taped holes.



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loveshisallis

02-07-2008 19:19:04




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 19:16:37  
I didn't worry about the "R" 45 plugs, as the magneto did fire them while pulled out of the block, grounded. Buuuuu uuuuu ut , one fellow mentions that it may not fire them IN THE ENGINE under compression. Sooooo ooooo ooooo oooo, looks like I do plug shopping....?????!!!!!



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DickL

02-07-2008 19:26:57




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 19:19:04  
Never had one not run on R 45's. Might not run on carbon wires. R 45's seem to give out quicker than old 45's. I have two running on Champion J- 8's now. They always do anything I need them to do.

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DickL

02-07-2008 18:44:06




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
Take the plug out up by the fan and put your thumb over the plug hole and make sure it fires after you feel pressure. The wires are correct in the picture.

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36 coupe

02-09-2008 03:44:38




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 Re: Magneto fires/Engine won't! in reply to DickL, 02-07-2008 18:44:06  
Keep paint off spark plugs and distributor caps.Kids asked me why their old Packard wouldnt start.They had spray painted the head, spark plugs,wires and dist cap with aluminum paint.Started fine after paint was cleaned off.



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teddy52food

02-07-2008 18:14:33




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
What are the plugs gapped at? Maybe the mag doesn't have enough to jump the gap under compression. Make sure they are not resistor plugs or wires. Is the spark (impulse snap) happening at TDC?



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leroy in ne

02-07-2008 17:56:32




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
check your firing order, some mag rotors turn opposite of distributers due to internal gearing of mags



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Ken Powell

02-07-2008 17:51:40




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
1) Make sure Mag has same length lug as distributor or it will not turn thus no fire...2)Make sure it is not grounded, or it will not fire...3) it's possible if you have supression core wires the mag can't overcome resistance...unlikely...4 It's possible mag has weak condensor allowing it to fire at atmospheric pressure, but not at pressure...also unlikely...most likely a ground issue...Good Luck

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Andy Motteberg

02-07-2008 17:39:22




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
Is the carburetor & fuel system in good working order?



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Janicholson

02-07-2008 17:33:18




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
Take any wire you have connected to it off. (except the plug wires and center High voltage mag wire) it can be as simple as the fact that mags are grounded to stop, not supplied with voltage to run. JimN



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IH2444

02-07-2008 18:40:46




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 Re: Magneto fires/Engine won't! in reply to Janicholson, 02-07-2008 17:33:18  
I suspect this to be the problem, just moving the wire from the dist to the mag.



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JT

02-07-2008 17:26:16




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
Do you mean the engine will not fire, or the magneto looses fire? If the mag looses fire, check your kill switch, if you are going from distributor to magneto igntion, the switches are not the same. If you are talking that the tractor will not fire and run, but will with distributor, did you use same plug wires? Are they a copper cored wire? A couple things to check.
Jim



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El Toro

02-07-2008 17:23:25




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
You have fire from the mag when it is off the tractor, set the mag on the engine without installing it and see if you still have fire. You may have a grounding problem causing the mag not to fire. Hal



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Gene Davis (Ga.)

02-07-2008 17:16:55




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:03:46  
Is the impulse working?



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loveshisallis

02-07-2008 17:45:59




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 Re: Magneto fires/Engine won't! in reply to Gene Davis (Ga.), 02-07-2008 17:16:55  
The impulse is working , and the magneto will spark mounted on the engine, witih all plug wires off. I turn the crank by hand , hear the impulse snap, see the spark but the engine will not fire. There is no ground wire. Just the tab. I have been over this and checked and rechecked the timing and am , for now , at a loss. the engine will run fine with the factory distributor ignition, just clarifying here.

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old

02-07-2008 17:58:39




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 Re: Magneto fires/Engine won't! in reply to loveshisallis, 02-07-2008 17:45:59  
Sounds like you may have the plug wires on 180 out or 90 out. I would try switching them around and see what happens



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Oldcraneguy

02-09-2008 08:27:11




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 Re: Magneto fires/Engine won't! in reply to old, 02-07-2008 17:58:39  
Seems like it would have to be crossed up wires dont it Old, If it runs fine on the distributor it cant be fuel/compression problems and id bet that any plug/wire combo that a dist. will fire a mag will fire better. Be interesting to hear how this one comes out.. Don



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old

02-09-2008 08:44:03




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 Re: Magneto fires/Engine won't! in reply to Oldcraneguy, 02-09-2008 08:27:11  
Yes it would. Plus on some mags they turn the other way so hooking up the wires are back wards of a distributor and that seems to get people at times. I know on the FMJ mag the rotor turns the other way and thats probably what is causing him the problem



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