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720 gas starting problem

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Graber at SD

06-15-2000 17:39:48




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My 720 gas will not start while the starter is engaged. If I push the starter till it just starts cranking and then let off it fires and starts.Battery is strong so what is going on?It seems that the starter somehow cuts the current to the distributor.I can figure most of these little problems out but this one has me baffled.HELP!




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Steve

06-17-2000 11:46:30




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 Re: 720 gas starting problem in reply to Graber at SD, 06-15-2000 17:39:48  
We have a 720, did the same thing. The wire leading from starter selenoid to reister got pinched under the flywheel cover when starter was rebuilt. Worked fine this way for a long time then it started leaking curent to ground. Some times the tractor would start right some times it would start when you took your foot off of starter button. Very frustrating at the time.



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Steve

06-17-2000 11:45:09




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 Re: 720 gas starting problem in reply to Graber at SD, 06-15-2000 17:39:48  
We have a 720, did the same thing. The wire leading from starter selenoid to reister got pinched under the flywheel cover when starter was rebuilt. Worked fine this way for a long time then it started leaking curent to ground. Some times the tractor would start right some times it would start when you took your foot off of starter button. Very frustrating at the time.



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Linwood

06-16-2000 09:30:54




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 Re: 720 gas starting problem in reply to Graber at SD, 06-15-2000 17:39:48  
On at least some of the 720s, the resistor bypass is built into the starter button. The button has three terminals, one hot, one to the solenoid, and one to bypass resistor to coil. Check to see if yours is set up this way. These buttons did give trouble.



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John T

06-16-2000 07:30:10




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 Re: 720 gas starting problem in reply to Graber at SD, 06-15-2000 17:39:48  
Graber, I agree with Clooney there as to the cause, so I will only add a troubleshooting tip. On the - side of coil or on the ballast resistor terminal that goes to the coil - , there should be two wires. If you disconnect both of them and turn the ignition on, one of them should show voltage and none on the other. On the one that shows no voltage, engage the starter and (ONLY) when the starter is cranking, it should show voltage. If its not, either the wire is broken that leads to the I on the solenoid or the solenoid is bad but I bet its a broke wire between there and the starter solenoid. The one wire comes from the battery to the ignition switch then through a series ballast resistor, while the other comes from the starter solenoid and is 12 volts ONLY when the starter is engaged so it raises coil voltage momentarily to aid in starting when cranking lowers the battery voltage. Ol John T in Indiana

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clooney

06-15-2000 18:12:15




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 Re: 720 gas starting problem in reply to Graber at SD, 06-15-2000 17:39:48  
Graber, that 720 has a "by-pass" starting system on it that runs a wire from the starter solenoid to the ignition coil to put 12v to the 6volt coil during cranking, then when it quits cranking a resistor in the wire from the ignition s/w to the coil takes over & lowers the coil voltage to 6-8 volts.If you have a volt meter put it on the coil terminal that the wire from the ign. s/w attaches & see if it has 10v or higher during cranking. By the starting explanation you gave it sounds like you have a low battery (test it with a volt meter while cranking) 11+volts, or high resistance in the battery cables ( check voltage at starter terminal during cranking (should be 10+ volts). It might be as simple as having too small of a battery or batterys in the tractor (test by using jumper cables from another GOOD battery). You should check the wire from the starter to the coil to make sure it is there & good also.

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Graber at SD

06-15-2000 20:25:49




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 Re: Re: 720 gas starting problem in reply to clooney, 06-15-2000 18:12:15  
Thanks clooney, I will check it out.My battery is big enough and good enough to crank that thing for five minutes straight if I wanted to. It always started right up for the last 7 years so maybe a wire came loose or has a bad connection somwhere between the starter and coil



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Haybaler

06-16-2000 05:51:21




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 Re: Re: Re: 720 gas starting problem in reply to Graber at SD, 06-15-2000 20:25:49  
My 730 did the exact thing. Started fine for years then started throwing the same fit yours is. Set up the wire that Clooney is refering to on advice from a John Deere mech that started on 730's when they were new and the problem went away. My two bits. HB



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Andy

06-18-2000 06:21:35




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 Re: Re: Re: Re: 720 gas starting problem in reply to Haybaler, 06-16-2000 05:51:21  
I would just take a piece of wire and jump from the batt+ side to the input side of the coil. crank/effect....



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