8N front mount, no spark

A few weeks ago, after sitting for some weeks, my
battery in my 1948-early '49 8N needed a recharge.
After recharging, it lost its charge again the
next day. After cleaning the batter cables it
seems to hold its charge now.
However, the Ammeter had not been working so I
decided to swap that out at this time (before
Winter). The new Ammeter did not work so I
decided to swap-out a new generator (which I had
acquired a few years ago, but rebuilt the old one
instead) and while I was at it, replace the old
wiring harness with a new one that I had purchased
some years ago with the intention of doing that
someday in the future. Also, inasmuch as I was
not sure if the battery was charging (suspected
generator, no working Ammeter to know for sure), I
opted to replace the old Voltage Regulator also.

Long story short, with new wiring harness, new
generator, new voltage regulator, the tractor will
not start. With key on, and a spark plug attached
and rounded to the engine, no spark to the plugs.
So, as a test, I put the old voltage regulator
back in...still no spark to the plugs.

When I opened the the new wiring harness, I used a
continuity device to make sure of correct wire and
labled both ends of each wire to prevent incorrect
wiring.

I followed the following wiring schematic
faithfully:

http://www.myfordtractors.com/12volt03.shtml

As far as wiring goes, the only things I have not
replaced are the ignition switch and the terminal
block.

Any suggestions on how to determine why no spark
at the plugs?

With the key on and points open make sure you see battery voltage at the coil.

No spark has absolutely nothing to do with the charging system. In other words you can have spark without even having a generator or alternator or voltage regulator or amp meter on the tractor. Spark has everything to do with the correct voltage to the coil and the points opening and closing. So, jump a wire from the non grounded side of the battery to the top of the coil and see if you now have spark. If not, the problem is inside the distributor. Time to remove the distributor and replace the points.

6v or 12v?

If it's 12v, tell what resistors you are using.

" I put the old voltage regulator
back in...still no spark to the plugs."

That's not surprising as the v/r isn't in the ignition circuit.

" I followed the following wiring schematic
faithfully:

http://www.myfordtractors.com/12volt03.shtml"

Which might be the problem if your tractor is 6 volt.

First, charge the battery. (see tip # 60)

You need a strong battery to:

1. Close the solenoid

2. Spin the starter

3. Engage the bendix

4. Provide voltage to the coil.

As the battery gets weaker, the first thing to fail is your spark. If the battery is almost totally dead, all you will hear is the solenoid clicking.

In addition to charging the battery, chances are you need new cables as well (tip # 41). And, don't forget to clean all the grounds, to include the mating area between the starter & the block.

The more current you use to spin the starter, the less you have for the ignition.

After the battery is fully charged, check it per tip # 49.

Then, as old said, check for battery voltage at the top of the coil (points open) and about half that w/ the points closed.

If you don't get battery voltage at the top of the coil w/ a fully charged & checked battery, run a jumper wire from the battery to the top of the coil.

Post back w/ results.
75 Tips

Went out to so some checks on the 6-volt 8N. Found voltage to terminal block and all the way to the coil as suggested. Got to thinking...maybe I was not patient enough with the turn-overs expecting it to start. Tried again, it started and it is giving me just short of 10 amps on the ammeter. The no-spark at the plug must have been due to a poor ground on the block (rusty manifold really).

I guess I can sell the old 3-brush generator to someone who wants it for a restoration project.

In short, everything is working fine, would have avoided a lot of worry if I had just given it a few more cranks to start.

Glad you got it running!

" The no-spark at the plug must have been due to a poor ground on the block (rusty manifold really)."

Yep.

That's why you need an adjustable gap spark checker:

http://www.amazon.com/Thexton-THE404-Spark-Tester/dp/B0002STSBM/ref=sr_1_1?ie=UTF8&qid=1411066950&sr=8-1&keywords=adjustable+gap+spark+checker
75 Tips