No spark at plugs. Help!!!

Sun Sep 04, 2011 4:57 pm

My tractor ran properly. I had to replace a rod bearing and took it apart..more apart than required. I replaced bearing, put the tractor together, watched the great 8min video on static timing and nothing. I have a spark from the coil (12V w 6v starter) to the mag when I take the ground off and touch the mag but I have no spark at the plugs. I've checked connections and looked at the before pics I took before taking apart the tractor and compared to the after but nothing. Please help.
thanks, David

Re: No spark at plugs. Help!!!

Sun Sep 04, 2011 5:09 pm

Pull the distributor cap and make sure the rotor is turning when the engine is cranked. Then make sure the timing marks are aligned on the mag rotor and drive gear. Not only does the mag need to be in time but the rotor has to be in the right position when the mag fires so those timing marks are as important as getting the mag on right. Since you have spark at the center wire you need to make sure the rotor is in the right spot at the right time.

Re: No spark at plugs. Help!!!

Sun Sep 04, 2011 6:33 pm

I'll check those marks. I didn't have a spark at the center wire but the small wire that comes from the coil to the bottom of the magneto. I'll match up the two marks that you mentioned and try again. thanks, David

Re: No spark at plugs. Help!!!

Sun Sep 04, 2011 6:51 pm

Your comments give rise to other questions - is this a magneto functioning as a magneto? Or a magneto converted to battery ignition or is it a distributor ignition? The only wires external to a magneto are the high voltage output and the kill wire on the side of the distributor. If you are seeing a spark at the primary terminal of an external coil that is normal. Spark at the output is totally different than spark at the primary side.
I suggest you clean and gap the points. This could be a points or condensor issue.

Re: No spark at plugs. Help!!!

Sun Sep 04, 2011 8:32 pm

Thanks Bigdog,
The spark is if I remove the kill wire and then touch the small terminal it attaches to. I'm lost as to the other questions you have asked. I know it is 12v with 6v starter. The coil(?) is small cylindrical and mounted on top of the block. It has one large wire attached that goes to the middle of the distributor. it has a positive terminal and it has a negative terminal which also is the kill wire. My points are new and I did take t hem and check and adjust the gap.
thanks again,
david

Re: No spark at plugs. Help!!!

Sun Sep 04, 2011 8:36 pm

Maybe a photo would help clear things up.

Re: No spark at plugs. Help!!!

Sun Sep 04, 2011 8:41 pm

In the Operator's Manual for 1950 or so Cubs are photographs of the magneto and battery powered ignition systems.

If it's a battery powered ignition system and you replaced the points - check to see if the spring on the points and condensor are not grounded to the distributor case. The spring and consensor wire go on top, then the insulator which is next to the case.

Re: No spark at plugs. Help!!!

Sun Sep 04, 2011 9:01 pm

You have described what is normally referred to as a distributor or battery ignition system. The spark you note is the circuit being completed. If you take a high voltage wire (spark plug wire or coil output wire) and hold it close to the tractor frame you should get a spark from the high voltage lead each time you touch the wire (the one you have been working with) to the side terminal. That wire is not a kill wire it is a voltage supply wire. Follow Eugene's suggestions and also clean those new points. They may have a corrosion proof coating on them.

Re: No spark at plugs. Help!!!

Mon Sep 05, 2011 11:33 am

So I made sure the marks lined up on the mag rotor and drive gear, filed the points, reset point gap, retimed engine and success! It runs...
Thanks everyone for your help..please be sure to see my next topic as my need for advice never ends.
take care,
David

Re: No spark at plugs. Help!!!

Mon Sep 05, 2011 11:49 am

Ain't it great when it all comes together!