8N with no spark - tested everything (I think)

I'm desperately in need of help. I bought a 1950 8N and ran it for maybe a 1/2 hour and the coil melted. It may have been damaged before and I just never checked it. Anyway, I replaced the coil, rotor, battery and points (plugs too but the spark never got that far).

So here's my problem. I have no spark to the plugs. I get juice to the new coil as soon as I turn the key but when I attach it to the distributor and cap, that's where the power ends. If I remove the cap from the distributor and touch the tester to the points (once the coil is touching it), I get no power. If I detach the distributor from the block and attach everything, I do get power to the rotor, distributor, etc. But when it's bolted on the block - nothing.

I've thoroughly cleaned the distributor from any loose gunk or anything, but still no spark. What am I doing wrong?

The 8N is a six volt system with positive ground. Please help!

Thanks in advance!

Thanks again!

In one of my lives I was a teacher so I’ve a prepared response for use on this problem. In another I was an electronics engineer so I will rotate a flat front tire to the back to see if it’s still flat. In another I was a clown/idiot. Because this is a prepared response I’m assuming the individuals electrical diagnostic skills may be lacking. I hope I’ll not appear to bloviate but will most likely be too verbose. I’ll try to strike a happy medium while adding my 2¢ to all the great responses you’ve already gotten. I hope your problem isn’t my last possibility as it is the most expensive.

I’d first be concerned with what melted my last coil before trying to get it started again. Multiple coils can get expensive. Electrical issues can be approached with an inexpensive voltmeter/resistance tester (multimeter). Some folks are intimidated by the device. If you aren’t don’t be offended by my step-by-step it may help someone else.

- - - - - No Spark Diagnostics - - - - -

Either the coil was old (end of life), wrong voltage, or an over voltage condition took it out (thereby releasing the magic smoke). For some PFM reason some “N’s” go through coils faster than others.

An important component you didn’t mention testing/replacing is your ignition resister. You can test it for resistance but it’s hidden on the firewall behind the tool box. I would 1st cut the problem child in half (at the coil).

The below procedures I learned from (Louis) Smith Tractor, Coweta Oklahoma. He specializes in N model Fords. If you’re in the area he is the Go to Guy.

Head to Waist (From Battery to Coil)

You should read approximately 3.5Volts between ground and the wire at the top of the coil (with the key turned on). If anything other than approximately 3 volts you’ve eliminated the distributor/coil assembly.         • No voltage at top of coil = an open somewhere between the battery and the coil. That would require further testing at various points between ground and each side of ignition (key turned on) and each side of resistor. You should get 12 volts each side of the switch and the key side of the resistor. You should get 3volts at the Coil side of the resistor. A 0Volt reading indicates a broken wire, or failed component.
        • Too high voltage means shorted resistor. This could cause other components to release the magic smoke. (Once the magic smoke has been released the component no longer functions as it should.)
If 3.5Volts is detected diagnose the 2nd half.

Waist to Toes (Through Coil to Plugs)

If you’ve access to a 12/6volt battery charger I recommend bench testing (isolating) the distributor/coil assembly off the tractor. Caution: 12Volts will probably damage your coil.
Concept: By running 6volts through the coil/distributor assembly (safely for a few minutes) you can test for spark at a spark plug wire port by spinning the points.
Setup: With the charger unplugged set it to 6Volts/Manual. Connect the Positive lead to the terminal at the top of the coil. Insert test probe (sparkplug wire or screwdriver) into any sparkplug port in the distributor cap. (Note: A sparkplug wire with sparkplug attached (with its body grounded to same ground as the distributor) works best. If you’ve enough hands a screwdriver inserted with approximate gap to ground also works.
Procedure: Turn on the charger and operate the distributor by turning the points on the back of the distributor where the engine would. You should see a good spark with each complete revolution of the points.

Spark = Assembly is good.

No spark = Fault in this assembly. Further diagnostics are required for the individual components.
Some problems seen are:
Coil bad
Coil spring not making contact with distributor
Condenser bad or shorted
Points not set or fused
Wrong points used and not opening
Rotor button lost its spring on top

If the bench tests work and 3.5Volts are present at coil when installed on the tractor.

Bump the starter and see if the distributors drive assembly moves. If not the drive gear at governor is stripped and not rotating points. OUCH!

Hope this helps.

Best Regards;
Elton

Persimmon Place
Bristow, OK

It may be that someone previously has had problems with the paper insulator where the flat copper conductor and the wire from the points are mounted to the distributor plate. It is a common place for the distributor to ground out.

If in fact the distributor is grounded out internally somwhere you keep trying and are going to fry another coil. It is the same as having the ignition switch on with the points closed and the engine not turning. It will fry the coil every time in just a few minutes.

You must also have a good ignition resistor in the circuit to the top of the coil. It is the ceramic thingy at the terminal point under the dash below the ammeter and it has a small wound wire through it. If that resistor has been bypassed that also will fry the coil. Especially if the distributor is grounded out somehow.

Zane

Bruce!

The connector for the condenser was touching the back of the distributor and grounding it out. Me and my buddy attached that thing probably 1/2 a dozen times and each time we must have done it wrong. Took a look inside the distrubutor, saw it was touching, readjusted it standing in the field in a thunderstorm, and voila! Spark! And she fired right up!

Bruce, I owe you a beer.

Thanks everyone. This forum has been very helpful!

Good Luck duey

You also have to be sure that the points are opening and closing. With the distributor on the bench and the coil attached check for continuity from the terminal at the top of the coil to ground -- it should vary from zero to infinite as the points open and close (as you turn the drive tang).

Roger

I did spin it off the block and did get power to all the points (just a tester light, not a multimeter) but again, when bolted to the block, I get nothing.

Everything seems like it should work (the lament of any junior mechanic, eh?). I just don't understand why it would ground out when mounted to the block. That's when I don't get a thing.

I will check to see if the are opening and closing. Would that not allow me to see power going to the points if it were only opened or closed? Even if the coil has power and is touching it?

When you reattach your distributor and hook up power to the top of the coil you should be seeing battery volts with the points open and about 3.5 volts with the points closed.

Roger in MichigaN