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720LP Electronic Ignition

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Bob K

07-11-2002 09:54:55




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My newly-acquired 720LP came with electronic ignition and I'm having problems starting the tractor. When I pull start it, she fires right up, but when I crank her over with the starter, it's very hard to get her running. (Battery was charged overnight so I know there's enough juice.) The coil (installed new with the ignition) gets real hot while I'm cranking the engine and never cools off even after running the tractor for a couple hours.

I took my VOM to the coil and here's what I found:

switch "on", engine not running: 12+volts

switch "on", starter engaged: 1-2 volts

switch "on", tractor running: 2.2 volts

Plugs are clean and gapped to about .025". I haven't traced the starting circuit yet, but was wondering if the voltages I'm seeing across the coil is typical of the electronic ignition system.

I need to see if it's wired to feed 12 volts to the coil during cranking and that the ignition switch is working correctly. Should the starter on the 720 have that extra 12-volt terminal for direct feed to the coil when cranking?

Your responses are much appreciated!

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ChuckW

07-11-2002 12:40:37




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 Re: 720LP Electronic Ignition in reply to Bob K, 07-11-2002 09:54:55  
the wire from the starter called the 12V boost wire is not used with electronic....you use direct 12volt to the setup...there are only a few components to the electronic...1. the magnet donut 2. the senor pickup 3. the coil. Maybe somebody wired this through the resistor which would be incorrect...you need to wire directly to the coil.



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Clooney

07-11-2002 11:08:37




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 Re: 720LP Electronic Ignition in reply to Bob K, 07-11-2002 09:54:55  
Bob, as far as I know all LP's have by-pass starting [a wire from the starter switch to the ignition coil that by-passes the resistor] including your 720LP.
~You should have over 10 volts at the coil cranking & probably 7-8.5 running.
~It sounds like you have more than one problem. ~The by-pass circuit doesn't seem to be functioning.
~You have too much resistance in the coil feed wire or resistor for your coil.
~Maybe the electronic ignition coil you have isn't designed to use an external resistor.
~ One of the positive aspects on an electronic ignition system is the fact they use a transistor instead of contact points so they don't need [& usually aren't designed to use] a resisted coil to keep the distributor side of the circuit below 8 volts to protect the points.
~You could also have a polarity problem, but that shouldn't lower the coil voltage to the values you are seeing..... ..... .. .....

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Bob K - Thanks Clooney

07-11-2002 11:32:09




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 Re: Re: 720LP Electronic Ignition in reply to Clooney, 07-11-2002 11:08:37  
I'll check these things when I get home tonight. In a search of all the archive posts on the subject, I saw one that mentioned something about the external resistor not being necessary with the electronic ignition. I'm going to go through my set-up more thoroughly to see how it's wired. Thanks again for all your help to all of us.



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Jack

07-11-2002 10:49:36




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 Re: 720LP Electronic Ignition in reply to Bob K, 07-11-2002 09:54:55  
I went ahead and got a coil with my electronic ignition but the person that sold it to me said that the coil needed to be at 3ohm at least and have an internal resistor.Does yours have an internal resistor?Does your tractor still have the generator and is it hooked positive ground or negative ground?



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Bob K - positive ground

07-11-2002 11:05:46




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 Re: Re: 720LP Electronic Ignition in reply to Jack, 07-11-2002 10:49:36  
It was converted to an alternator but it is not connected (doesn't work). I have to charge it every week with an external charger to keep the battery up. Plan to fix this soon. The tractor is positive ground.

I'm going to do a little more sleuthing on the coil and see what brand of ignition I have. I'm hoping the previous owner bought a matched set of parts for the system and that the coil is the right one. He was really into modifying tractors and pulling in tractor pulls. I'm hoping he knew what he was doing when he installed this ignition system.

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Jack

07-11-2002 12:15:37




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 Re: Re: Re: 720LP Electronic Ignition in reply to Bob K - positive ground, 07-11-2002 11:05:46  
See if you can find out whether or not the electronic ig.is for a positive or negative ground for sure.If you are running a positive ground than you will have to change this to accomidate the alternator.The alternator will probably be a negative ground system.They make two kinds of electronic ignitions for these,one being for the pos gr.and one for neg.ground.My instructions say not to connect them wrong or failure of the pickup would occur.Hope this helps Bob.Jack(TN).

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ChuckW

07-11-2002 10:25:42




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 Re: 720LP Electronic Ignition in reply to Bob K, 07-11-2002 09:54:55  
I've run several of these electronics and have 3 tractors with unit. I don't know your setup, however the ones I have use 12volt. There is a difference in negative and positive ground setups. Always buy the coil with the setup. Genesee electronics is my setup.



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