Electrical Mysteries

Had my 8N die a couple of weeks ago and discovered I had no spark. I decided that since things looked a bit worn, might as well replace the points and condenser, plugs, new distributor and rotor, new coil, and new regulator.

Everything worked fine and she started right up. I ran the tractor for about two hours doing some mowing and it suddenly died again. When I checked the plugs I am getting no spark again.

Can anyone give me a suggestion as how to step-by-step isolate the problem? I do have a Volt/ohm meter so I should be able to track it down.

Any ideas as to what might be causing this problem?

To quote one of the real smart guru's here on the list, 'follow the volts'.

If you've got an electrical problem.. say spark... start at the first connection, and work your way to the plug. Be safe.. start right at the battery.. then switch, resistor ( if equipped), and so on. ( by the way.. this troubleshooting techniques works with nearly any kind of electrical problem... simple process of elimination.. start at a known 'good' area, and work away from it till you find the fault. )

A couple things to look for and be aware of. 'open'.an open circuit is merely an incomplete conductive path... broke wire, bad terminal, etc. 'short' the normal circuit path is interupted ( usually directed to ground ).. and thus 'shortened'.. or shorted.. bare wires, rubbing, bad insulation, etc. Shorts usually leave everything upstream from the short, 'out of the circuit', and everything upstream, heavilly loaded... shorts cause wires to smoke..etc.. )
'resistive shorts'.. almost a short... but just enough corrosion or insulation to make it hard to track down... frayed wires.. corosion between two contact points.. causing cross conduction.
'resistive connections' i.e. dirty/loos connections that cannot pass their rated load of voltage/current due to insuficient contact surface area / conduction capacity of the wire, etc. dim or flickering lights are a symptom of a resistive contact in a lighting circuit.
Electrical problems are easiest to diagnose when they are constant. Intermitant problems come and go and are much harder to troubleshoot.

Good luck..

Soundguy

A few more facts will help:
1) Is your N a front mount or side mount distributor?
2) Do you have a 12 volt conversion?
3) Did you check the little copper grounding strap inside dist (connects with points terminal)?
4) Did you check to see if your points slipped?
5) Did you check your rotor to see if the spring is broken?

Sometimes new parts/new installations of parts go awry.

This is a late model 8N with side mount distributor. It's not a 12 volt conversion but the original 6 volt set-up. Points seem to be opening and closing with the right gap. I did not think to check the wiring inside the distributor to insure all connections as as they should be but I will do that.

How to check for a good coil (and therefore everything up to that, I guess)? Is it as simple as turning the engine over with the key on and pulling the coil wire from the distributor and looking for a spark from the coil wire when held near ground?

Yes, you can pull the coil wire and check for sperk against the block, but insulate your hand grip.

I've lost spark on Chigger in the past for these reasons:

1) My coil was BROKEN by bouncin' up and down in its clamp. It would be rare though for your coil to suddenly give out as you describe. Don't think that's your problem.

2) The rotor spring developed an almost invisible hairline crack where it i clamped to the brass tip. Simply didn't have enough contact or electrical transfer to facilitate spark. Others on the Board have reported this happening. 3) There is a little 3/4" long x 1/4" wide irregularly shaped copper strap that connects to the points terminal (same one you connect the condensor to) and to the screw that goes thru a tiny tubular insulator thru your dist housing that the coil lead connects to. I was CHEAP and didn't replace my strap with the proper strap. I took a little piece of wire and used it instead. That wire fatigued over time and developed an internal break I couldn't see. That grounded out my whole dist system. further, if you DO still have a proper strap, the insulator that the screw goes thru must be in good shape or the screw will ground out the dist since it connects to the strap.

4) Points slipped. That .024-.025" gap is a MUST and you have to verify it's still there. I have to regap Chigger's every 10 hours or so or 50 starts whichever comes first.

5) Though this hasn't happened to me, make sure your coil-to-dist cap wire is making good contact/isn't broken.

If above all checks out, take a piece of wie and connect it to both leads of your kill switch. Then crank. If fires up and runs, your kill switch is bad.

Yes, you can pull the coil wire and check for sperk against the block, but insulate your hand grip.

I've lost spark on Chigger in the past for these reasons:

1) My coil was BROKEN by bouncin' up and down in its clamp. It would be rare though for your coil to suddenly give out as you describe. Don't think that's your problem.

2) The rotor spring developed an almost invisible hairline crack where it i clamped to the brass tip. Simply didn't have enough contact or electrical transfer to facilitate spark. Others on the Board have reported this happening. 3) There is a little 3/4" long x 1/4" wide irregularly shaped copper strap that connects to the points terminal (same one you connect the condensor to) and to the screw that goes thru a tiny tubular insulator thru your dist housing that the coil lead connects to. I was CHEAP and didn't replace my strap with the proper strap. I took a little piece of wire and used it instead. That wire fatigued over time and developed an internal break I couldn't see. That grounded out my whole dist system. further, if you DO still have a proper strap, the insulator that the screw goes thru must be in good shape or the screw will ground out the dist since it connects to the strap.

4) Points slipped. That .024-.025" gap is a MUST and you have to verify it's still there. I have to regap Chigger's every 10 hours or so or 50 starts whichever comes first.

5) Though this hasn't happened to me, make sure your coil-to-dist cap wire is making good contact/isn't broken.

If above all checks out, take a piece of wie and connect it to both leads of your kill switch. Then crank. If fires up and runs, your kill switch is bad.

Where did you find a replacement part for the insulator and copper strap in the distributor? I am thinking this might be my problem as it looks like it is really in bad shape.

If it runs great and then instantly loses spark, I'd say it's some sort of short in the system, maybe a hidden bare wire in the distributor or something like that.

Is it a front mount distributor or side mount? 6V or converted to 12v?