520 ignition question

I just bought a 520 today. I noticed that it will crank and crank and crank and then finally fire.
But if cranked and let off the starter it fires.
I rememeber reading something about when letting off the starter then it starts, verses cranks for a long time and finally fires, but cant rememeber.
It has a different ignition switch on it, need to replace with correct one, possible that could be related to issue?

Also if anybody has parts for 520 please e-mail me.

Thanks

It might have a 12 volt crank stud on the starter seleniod that runs to the - post on the coil, if still pos ground. That wire may be broken off, check it out first before replacing a lot of other parts.

Besides the previously mentioned missing starting bypass circuit. There could be a 12V coil on it and/or the coil polarity was connected backwards.

A few things come to mind.

If the battery is weak or the starter is drawing excess current or perhaps there are bad connections or grounds (on starting or ignition circuits), while cranking the voltage can be greatly reduced therefore the spark is weak while cranking, but as soon as you let off the starter the voltage rises so the spark is stronger and she fires. Check all the battery and starter and ground connections, there may be a carboned resistive connection in the circuit. The ignition switch could also be resistive dropping voltage resulting in a weak spark. If you put a meter on the battery while cranking the voltage normally drops some (maybe 10 to 11 or so), but if its dropping down to like 9 or so (but depends on battery and starter) that can cause a weak spark. Cause may be faulty starter motor or again a bad battery or starter or ground connection.

If it has the original ballast resistor and by pass while cranking system all intact and working, that should help alleviate the problem above since the ballast is then by passed while cranking so the spark is stronger. HOWEVER if the ballast by pass circuit isn't working (loose or no wire from starter switch to coil or faulty starter switch) the spark while cranking isnt as strong as it would be if the by pass system was all intact and working. See if there's a small wire up from the starter switch to the coils input
and if it gets hot voltage when the starter switch is depressed??? That's how it by passes the ballast voltage drop.

If its original it would have a 6 volt coil (or one labeled 12 volts for use with ballast etc) but if it got changed to a 12 volt coil and the ballast is still in place the spark will be weak.

Low voltage on the coil caused by a bad ignition switch or a loose or carboned connection or a poor ground somewhere in the primary ignition circuit can cause a weak spark. Turn her on and put a voltmeter on the coils input and measure the voltage to see if its low. If it has a working ballast and points are closed Id expect maybe 6 to 7 volts on the coil since the ballast drops around 6.

John T

Look at the contactor button on your starter. Does it have an extra small wire coming off of the side of it? If it does, that should be connected in with the wire from your switch to your coil after your ballast resistor. That gives you full 12 volts to your ignition while cranking to give more spark and easier starting. My 720 would do what yours is doing because the button was bad. Tractor would still crank but it wasn't contacting on the side terminal to send the 12 volts to the ignition. Good luck!

In the archives type in: "Wiring a 520 Confused is an understatement". Read what these gentlemen have to share.

Try to locate JD PARTS CATALOGUE PC-527-(May-66)
View page 102

The best JOHN DEERE ELECTRICAL MANUAL is SM-2029.Every 2 Cylinder owner should own this manual
Bob.....

Can it be said that "Great minds think alike" lol looks like we had the exact same thought:

"HOWEVER if the ballast by pass circuit isn't working (loose or no wire from starter switch to coil or faulty starter switch) the spark while cranking isnt as strong as it would be if the by pass system was all intact and working. See if there's a small wire up from the starter switch to the coils input and if it gets hot voltage when the starter switch is depressed??? That's how it by passes the ballast voltage drop."

Now if we were right??? or it was one of the other many possibilities????????

Fun chat, hope we get him going

John T