Electrical Issue? I’m out of ideas....

[AimmeAshley]

Just throwing this in.. I just had a similar issue with a friends older Craftsman Indy Edition mower.. Tested checked gave up.. replaced the ignition switch and all the safety switches except one which I unplugged (2 wire) seat one..It would not start or It would start and sometimes die right off and sometimes you could get started mowing then it would shut down... Just for drill I pulled the PTO switch off a different mower and exchanged them.... Everything worked great.. ordered a new PTO switch and He has been mowing once a week and this was a month or more ago..

I guess I can start replacing switches even if they're checking out as good on my multimeter. Not sure if I'm at that point though. I've yet to remove the starter motor to check for a kink on the kill wire.

After a long day at work and having to make dinner most nights, I might have to do it during the weekend. It just takes some extra will power to really look at the mower on a weekday

 

[AimmeAshley]

To answer your question. Yes the kill wire would read ground, but with a higher resistance as you mentioned in another post. You are reading the ground through the coil. This is a simple coil schematic of the coil system, that may help explain it better.

Not sure if you have points or an electronic system on that mower, but this gives you an idea what the ignition switch is doing to kill the coil. And how you are reading a ground through the coil.

View attachment 56793

Thanks for sending this schematic! I think you're mentioning the kill wire, but I was actually asking about the kill tab on the ignition coil itself.

Are you saying the kill TAB is supposed to be grounded as soon as I bolt it on? Where is the kill tab on this schematic? Would it be considered the top left of the magneto?

I'm also not sure what a "points" versus "electronic" system means, but I think this is a "points" machine? There's no other electronics underneath the dash, if that's what your asking.

 

[AimmeAshley]

I have seen the LCD hour meter short internally causing it to go to ground. You might try disconnecting it

Thanks for your response! I'll try disconnecting it and seeing if that changes anything!

 

[bertsmobile1]

I go back to what was said in post # 4
Make up some short jumpers with a male spade on each end and jump the plugs according to how the switches would connect them
Do this one at a time thus you have bypassed the switch(s) till the problem resolves.
If this does not resolve the problem then there is a short or open circuit in the actual loom .
Armed with a circuit diagram start bypassing sections of the loom with longer wires, these will need a male on one end & a female on the other.
It is fairly common for a wire to fatigue at the crimp so depending on things like temperature or vibrations will make or break contact

 

[AimmeAshley]

Check your new coil and see if there is a tiny screw where the kill wire plugs on. If there is take the screw out and bend the edges back from the metal body of the coil and then plug your kill wire back on. I have found this on off brand coils. When the screw is in and you plug the kill wire on it grounds the coil out immediately. I had 2 coils like that.

Thank you for replying. Definitely no screw on the kill wire.

This is the one I ordered:

Amazon.com : Briggs and Stratton 595304 Magnet Armature, Black : Patio, Lawn & Garden

Amazon.com : Briggs and Stratton 595304 Magnet Armature, Black : Patio, Lawn & Garden

www.amazon.com

 

[lemerick]

The last one I worked on with the same issue the PTO lever had dropped down enough to not make contact with the safety switch and would not let the machine start. John Deere has a terrible setup on this safety and the tab on the lever just barely hit the plunger. After use of a couple of years there was enough play to allow the whole PTO arm assemble to drop down in the dash and not make contact with the safety plunger. The owner had everything replaced at a dealership for $200+ and within 2 months use was back to the same problem. I showed him how to pull up on the PTO arm before starting the mower and working it slightly to engage the switch so it would start. It is a pain but sure beats a $200+ fix that last less than 2 months!!

 

[BrianSki]

Thanks for sending this schematic! I think you're mentioning the kill wire, but I was actually asking about the kill tab on the ignition coil itself.

Are you saying the kill TAB is supposed to be grounded as soon as I bolt it on? Where is the kill tab on this schematic? Would it be considered the top left of the magneto?

I'm also not sure what a "points" versus "electronic" system means, but I think this is a "points" machine? There's no other electronics underneath the dash, if that's what your asking.

To answer your question. Yes the kill wire would read ground, but with a higher resistance as you mentioned in another post. You are reading the ground through the coil. This is a simple coil schematic of the coil system, that may help explain it better.

Not sure if you have points or an electronic system on that mower, but this gives you an idea what the ignition switch is doing to kill the coil. And how you are reading a ground through the coil.

View attachment 56793

It does look like this is a points machine... The points are usually under the flywheel. But you don't have a problem with that. I will break this down into sections.

Yes you are correct the tab on the coil is on the upper left. You should have a wire going to the points and a tab or wire going to the kill circuit. If you test the tab with no wire connected, it may show ground through the points, or through the coil itself. Since it runs with the wire connected, that seems to be working correctly.

I found another schematic of the wiring, but it may not be 100% for your tractor. It looks like there are 2 safety circuits.

One needs to be connected to get the starter to work. The PTO off (blades) and the clutch need to be pushed in to engage the starter. If the engine cranks (but no spark) that section would be ok.

Now the other safety section grounds the coil to kill the spark. When the switch is turned off, it grounds the wire that goes to the coil. Or when the seat is unoccupied WITH the PTO engaged it grounds the coil. (some tractors with reverse engaged with blades engaged it kills it also)

With your test meter, hook it to the wire that goes to the coil, with the wire disconnected from the coil. (The wire that runs when disconnected) When the key is in any position other than off, there should be no connection to ground. (infinity reading, toward the high numbers on the scale) If there is a low reading (close to 0), there is a short in the wiring or a bad switch. (remember key in run position) (Could also be whatever actuates the switch. If you find that wire grounded, you are on the right track. (I think you will)

If you find the connection grounded. (leave the meter connected) Unplug the safety switches one at a time to see if the reading goes to the high end of the scale. When it does you found the problem. You can also wiggle the wires to see if any are shorting against something, while watching the meter.

This should help you out. Let us know what you find.

 

[BrianSki]

T

With the ignition switch OFF, the resistance of the kill wire to ground is less than 1 Ohm, which I think is correct.
With the ignition switch ON, the resistance of the kill wire to the ground chassis is roughly 9.89 KOhms, which I'm not sure is considered shorted to chassis.

Ok, just went over this... With the ignition switch ON, the kill wire reads 9.89K. Is that with it disconnected from the coil?? If so, disconnect your safeties one at a time until it goes to an infinity reading. Something is pulling it to ground. You may even try to unplug the key switch too, to make sure that would not be the problem.

Not to confuse you more... I am trying to find where the points hook up to the coil. Maybe through the kill wire. That may be giving you the reading. But then it would not run disconnected. Sometimes easier to see in person. (or it may have some hybrid ignition??)

 

[BrianSki]

Isn't there a one way diode that can go wrong on these systems?
One of the symptoms are, no spark with the kill wire attached.

From what I seen in the schematics. The ones with a diode are 2 cylinders with 2 coils. The single cylinders did not have a diode.

 

[Telesis]

Just to clarify, this is NOT a points machine. I happen to have a 31R977 on my bench and with the coil removed, the resistance from the kill terminal to the laminations is 1.6 ohms(using a Fluke 87-V) as suggested earlier. I'm guessing Aimme that when you measured from the kill tab on the magneto, to ground, with the kill wire removed, you interpreted the very low reading as the tab being grounded.

I also want to confirm that the RIO switch(not the RIS on the dash) is in the tranny, and you can check it by measuring across the two nubs and verifying it only shorts out when switched into reverse.

As lemerick suggested, does the blade lever make good physical contact with the switch when the blades are not engaged? On my JD D105, there is a spring on that lever to make sure it pulls in the switch button when you disengage the blades. Is that spring there? Does it appear to be pulling in the switch appropriately?

Finally, the value you measured of 9.89K ohms is suspect. I'd like you to repeat that test(disconnected kill wire, resistance between kill wire and ground), but with the positive battery lead disconnected(so it won't start). That way you can share the value in all 4 ign switch positions(off, run w lights, run, start)

Finally finally, Rivets, you asked early on for the vin #. Do you have access to the schematic and if so, can you post here?