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Discussion Starter #1 (Edited)
Hi:

I recently had several new parts installed. Coil, points, condensor, plug wire and plug. Was out to cut the lawn this morning and it quit part way thru the first
round. Yellow wire running from wiring harness to headlights had come loose and grounded on the frame. I reconnected it and things continued. Cut around 90% of
the lawn and then it died. No fire. Would turn over fine but not getting any spark.

I did some diagnostics as follows:

- checked when key is in the ON position that am getting 12V at the + terminal on the coil. CHECK
- checked that I'm getting 12V at the seat safety switch. CHECK
- checked the points but putting my volt meter on the - terminal with black to ground and turned it over - NO METER MOVEMENT
so...does that mean the points are not working? Could bouncing around the lawn put the points out of proper spec??

Since it is turning over no problem, what could be causing the no spark condition? Could just bouncing around the yard cause the points to go out of proper spec and thereby no spark?

Ideas??
 

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Try reading voltage from the points positive terminal to ground with the switch on and the points open. If no voltage, disconnect the condenser from the circuit. If you get voltage, the condenser is shorted out. If still no voltage, take a voltage reading at the coil negative terminal to ground with the points open, if voltage, the wire from the coil negative terminal to the points is probably loose or broken. If no voltage, coil may be bad. You can do a primary resistance reading across the positive and negative coil terminals, should be around .4 to 6 ohms. You can also check the coil secondary windings from positive terminal to the plug wire socket on the coil, should be around 5k to 20k
ohms. Coil manufacturer will have the actual resistance values for that particular coil.
 

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You probably already checked, but make sure the points are actually making contact with each other when closed.
 

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I forgot to mention, you can test the condenser with your meter set to ohms. Hold the red lead on the condenser positive wire and the black lead on the condenser case. The meter should rise to infinity and stay there. Hold for 15-20 seconds. Any reading less than infinity, no good. Then hold the red lead on the case and the black on the wire, meter should rise and then fall back to zero. Disconnect the condenser wire before testing.
 

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Discussion Starter #6
Try reading voltage from the points positive terminal to ground with the switch on and the points open. If no voltage, disconnect the condenser from the circuit. If you get voltage, the condenser is shorted out. If still no voltage, take a voltage reading at the coil negative terminal to ground with the points open, if voltage, the wire from the coil negative terminal to the points is probably loose or broken. If no voltage, coil may be bad. You can do a primary resistance reading across the positive and negative coil terminals, should be around .4 to 6 ohms. You can also check the coil secondary windings from positive terminal to the plug wire socket on the coil, should be around 5k to 20k
ohms. Coil manufacturer will have the actual resistance values for that particular coil.
OK, I'll start with these tests in the morning. Thx for the input. Appreciate it. :bigthumb: I bought some 10 guage wire this morning to replace the wire from the - coil terminal to the points. I'm hoping that this is where things have broken down. I'll then do the tests as indicated and report the results.
 

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Discussion Starter #8
Try reading voltage from the points positive terminal to ground with the switch on and the points open. If no voltage, disconnect the condenser from the circuit. If you get voltage, the condenser is shorted out. If still no voltage, take a voltage reading at the coil negative terminal to ground with the points open, if voltage, the wire from the coil negative terminal to the points is probably loose or broken. If no voltage, coil may be bad. You can do a primary resistance reading across the positive and negative coil terminals, should be around .4 to 6 ohms. You can also check the coil secondary windings from positive terminal to the plug wire socket on the coil, should be around 5k to 20k
ohms. Coil manufacturer will have the actual resistance values for that particular coil.
OK, been working on this all day... I took the new parts I got from isavetractors.com (coil and condensor) off and tested them. Looks like they are both shot. New parts....geeze. No reading from + to - on Ohms. Nor on + to plug connector either or - to plug connector. No reading on the condensor either.

So, I re-installed the old coil which worked before and the condensor that was used with it. I get 12 V on + with key in the OK position with it. I also get 12V on the - terminal with key on.

Earlier this morning I took off the points and re-checked the .020 setting. There was no dirt or debris inside and there was no sign of damage to the points themselves. I took off the wire running from the coil - to the points to inspect it and it was in good shape. No burns or abrasions in it. I did a ohm reading on it to ensure it's in working order reading 0 with red lead on ohm meter on one end and black lead on the other.

We tested the old coil and condensor and when we turn it over, it is not putting 12V out the - side ...only around 5-6V. No visible spark on the plug either. We tried testing to see if the power is making its way from the - coil to the points and it is not. So...I'm not sure wtf is going on here. We removed the condensor from the - side of the coil to see if that was sucking up power and it made no difference.

Could the rectifier/regulator be a problem here? I thought it was only for charging the battery.

Not sure where to go from here...
 

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Mack, I can't say what's wrong but I believe (??) 5-6v on the negative side - of the coil is OK. There's an internal resister in the coil that will drop the voltage..this is to save your points. I kinda thinking you should have around 7-9v though.

Coil to points wire: Remove wire from coil and check continuity to points. If OK, remove points and check from fixed side of points to points base plate with an insulator holding points open. Next check from movable side of points to base plate...again with insulator between points. It's been a loong time since I've messed with points, but IIRC, the fixed side should should have continuity to the base plate and the movable side has an insulating bushing and should not have continuity to the base plate. The bushing could (??) be worn and your coil is constantly connected to ground...thus, no spark.

Hopefully, some one will correct me if I'm wrong on points continuity to base. Either way, one side should have continuity and the other shouldn't. Check it out and post findings. Bob
 

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Discussion Starter #10 (Edited)
Mack, I can't say what's wrong but I believe (??) 5-6v on the negative side - of the coil is OK. There's an internal resister in the coil that will drop the voltage..this is to save your points. I kinda thinking you should have around 7-9v though.

Coil to points wire: Remove wire from coil and check continuity to points. If OK, remove points and check from fixed side of points to points base plate with an insulator holding points open. Next check from movable side of points to base plate...again with insulator between points. It's been a loong time since I've messed with points, but IIRC, the fixed side should should have continuity to the base plate and the movable side has an insulating bushing and should not have continuity to the base plate. The bushing could (??) be worn and your coil is constantly connected to ground...thus, no spark.

Hopefully, some one will correct me if I'm wrong on points continuity to base. Either way, one side should have continuity and the other shouldn't. Check it out and post findings. Bob
I took the wire going from the - terminal of the coil to the points off this morning, cleaned it and checked for damage, burn marks, etc. It was in very good condition so I just put insulators on the ends near the terminals and put it back on. Did an ohm check and it read 0 ohms verifying that is was good.

RE: the points themselves, when connecting the J hook connector on the end of the wire, this may well be where I'm not putting it on the screw correctly. There is a metal flange that is spring loaded with the screw through it. I put the J hook wire end on that screw but on top of the metal. Is that correct?

You can see the metal flanged with the screw connector on the points in the picture. The screw is not installed on these points (old). but the J connector would be between the screw and the metal.

IMG-5798.JPG
 

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As I said, it's been a loong time! BUT I'm thinking that's correct. I'm thinking loosen screw, insert u-shaped wire terminal/connector under screw...I'm assuming this is what you call a j hook connector. This usually fits into a u- shaped piece of metal that wraps around the connector. Bob
 

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One last thought. Remove wire from coil to plug and check continuity. Don't hold meter leads to connectors with your hands...you'll be reading continuity through your body! Hold meter lead on one end with your hand and hold other end down with meter lead. Try twisting wire also. The connections have been known to corrode as well as the wire "burning" out. Bob
 

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Discussion Starter #13 (Edited)
One last thought. Remove wire from coil to plug and check continuity. Don't hold meter leads to connectors with your hands...you'll be reading continuity through your body! Hold meter lead on one end with your hand and hold other end down with meter lead. Try twisting wire also. The connections have been known to corrode as well as the wire "burning" out. Bob
Yes, it's a new part. I did notice that the connection on the pin inside the coil neck was not making a good firm connection. So, I pushed the boot back and crimped the connector so it makes a better connection to the pin in the neck. When I connected it and turned the engine over I noticed a bit of smoke from the wiring adjacent the coil. I think there may be a wiring snafu. I noticed after the engine quit this last time that there was a T connector block with the wires coming from the regulator/rectifier. This wiring junction had melted somewhat. There were 2 flat blade connectors in this. coming from the wiring harness were 2 pink wires and a black one. this may be indicative of a problem with the wiring.

Anyway, I re-did the wire check of the new plug wire using aligator clip on one side and the black lead stuck in the other end....so I wasn't holding either end. Ohms read 0 so should be a good cable.
 

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If you have defective parts from I save tractors I know Norman will take care of you.

Reading voltage on the - side.....the points allow a path to ground. It should average 6v.
 

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Discussion Starter #15
If you have defective parts from I save tractors I know Norman will take care of you.

Reading voltage on the - side.....the points allow a path to ground. It should average 6v.
Hopefully. He seems like a very decent guy. The problem seems like old wiring biting me in the ass. If the points are grounding out how does this occur? Does the electrical current making its way "to ground" inside the points case? ie: by being connected incorrectly ...something like that?
 

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Hopefully. He seems like a very decent guy. The problem seems like old wiring biting me in the ass. If the points are grounding out how does this occur? Does the electrical current making its way "to ground" inside the points case? ie: by being connected incorrectly ...something like that?
The points when closed connect to ground. That’s their job.
 

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Discussion Starter #17
The points when closed connect to ground. That’s their job.
I guess what I'm concerned about is there any way I could have connected the wiring to the points that would inhibit their proper functioning? My understanding of how the coil and points work together, 12V is sent from the + battery via the ignition. this power is sent to the points via the - terminal and is held there while the points are closed until the plunger pushes the points open to create the spark and complete the circuit. This electrical charge then returns to the coil and released via the center post to the plug. Is that correct in your understanding?
 

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I guess what I'm concerned about is there any way I could have connected the wiring to the points that would inhibit their proper functioning? My understanding of how the coil and points work together, 12V is sent from the + battery via the ignition. this power is sent to the points via the - terminal and is held there while the points are closed until the plunger pushes the points open to create the spark and complete the circuit. This electrical charge then returns to the coil and released via the center post to the plug. Is that correct in your understanding?
Close enough for figuring things out.


Condensers can be disappointing, doa or short lifespans. It happens. It should run rough without one for a quick test. When bad they can prevent running if still attached.
 

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Check that the points aren't touching the inside of the cover. That would short them out and cause a problem like yours. It happened on my 400 because the new points were slightly taller than the originals. Doubling the cover gasket would solve the problem.
 

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Here's a quick explanation of how the ignition system works: when the key switch is on, current flows from the battery to the coil.
When the points are closed it completes the circuit to ground and current flows through the coil primary windings building up a magnetic field around the windings.

When the points open, current stops flowing and the field rapidly collapses inducing a current in the coil secondary windings. Because the secondary has many more windings than the primary, the voltage is much higher, around 15,000 volts in this case. This voltage is high enough to cause an arc (spark) across the spark plug electrodes to ground. The cycle starts over again as the points close.

The condenser's job is to absorb current to prevent arcing and burning of the points as they open and close. It also helps collapse the magnetic field in the coil more quickly. To further protect the points from burning, a resistor is added to the coil reducing voltage by roughly one half. That's why the voltage at the coil negative terminal is much less than at the positive terminal.
 
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