Help with 8N and starting

I have searched the forums and it may be due to me not being able to read, but I have not encountered something similar to what I am experiencing.

In short, we can pull start this 8N and within 20-30 ft it is running, while the engine is still hot it will fire back up on its own. It runs smooth and sounds solid.

Things done so far:
Rebuilt Carb
changed wires and plugs
gap has been checked and rechecked

I've reviewed 75 8N tips and other documentation from this site, just looking for some guidance.

Thanks!

Welcome to the forum.
I would do a compression test to start with.

A weak battery and a starter that is worn can cause that. The worn starter draws more current so the weak battery's voltage drops. Now there may not be sufficient voltage to fire the spark plugs.

6 or 12 Volt? Front or side mount distributor?

If it has a 12 volt conversion, check for too much resistance in the coil input circuit.

(quoted from post at 21:36:20 05/06/21) ..... we can pull start this 8N and within 20-30 ft it is running, while the engine is still hot it will fire back up on its own

Click to expand...

I'm guessing that your tractor doesn't start conventionally when cold.
If that's the case, A worn out engine (low compression), or compromised ignition system are two common reasons for no start unless pulled. Engines turn over nice and fast when pulled. Loosening up, building compression and continuous turning over are some of the reasons they start this way. Some or all of those reasons can overcome why they don't start on their own. These are also some of the reasons why tractors start easier on 12 volts.

Royse and RM are telling ways to check some of this.

If it's low compression, the next step is to determine why it's low.

This is all great stuff, thank you very much!

It was converted to 12 volt, what is too much resistance in the coil input circuit? This is a front mount distributor.

I am in the process of acquiring a compression test kit with a 90 degree elbow.

Thank you guys!

Is this tractor new to you? You mentioned new plugs and wires but what about the points and condenser? Have you checked the timing? Does it have a ballast resistor or a ( 12v no external resistor needed) coil? Coil resistance should be around 1 1/2 ohms with a resistor and 3 without. Valve lash? Vacuum loss? (Spray brake cleaner around carb and manifold and listen for speed change). Breather clean?

My first thoughts were a very tired engine but you have other issues. Even a tired engine would fire up within five feet when pulled.

My grandfather and I have been working on this for the last two years, last summer we put it back together, but between nnalert, him having surgery and other events; it has kinda sat. This problem was present then, but we were still trying to figure out where the problem is; now that things are getting back to normal, I want to dive in and find the problem. I included a short video of it running and with me 'revving' it up. The points and condenser were replaced, I need to check the resistor as I am not 100% sure if it was removed or not. Breather is clean.

Video of it running:
https://imgur.com/a/MzV1Zvb

So the story behind this tractor is that he bought it from a hunting club who was trying to convert it from 6v to 12v; however they ran into issues (tractor and club membership), so it was decided to sell the tractor as is. But at this point it had sat for 2-3 years, so my grandfather took off the hood, removed the plugs, poured some ATF into each hole as we were initially unable to 'crank it by hand'. After letting it sit and soak, my grandfather eventually worked it free (when I say this keep in mind it was not a ram and jam, it was a slow process). While the hood was off he replaced the points, condenser, checked timing, cleaned the breather, finished rewiring, cleaned the carb, the bowl, and the tank. Fast forward to summer before Rona, we could periodically get the tractor to start on its own, but its random and frustrating. I am suspecting it is an electrical issue as that is no longer his strong suit, at 87 yrs old, he is becoming forgetful. I do not care though as I enjoy spending time working on this with him, but I want to get it running so he can feel that accomplishment again.

Sorry for getting sappy, but I fell in love with these tractors when I was a kid, and I feel blessed that I have been able to work with him on this. I am hoping to get over tomorrow or some day this week so I can review the wiring as I found the following wiring diagrams (http://www.myfordtractors.com/12volt03.shtml), and this is the specific wiring diagram I want to review (http://www.myfordtractors.com/images/WIRE-12-47-1w.jpg) when I am there.

I appreciate your patience and guidance on this, I want to learn more, but its almost like drinking from a fire hose ha.

K. Larues' diagrams are good but I find JMOR's easier to read.
He has many, so if this isn't the one you need, Google them.

I understand and appreciate the sentimental value.
The fact that it was set up makes me want to double down on the compression check.

This is great thank you! I am ordering a compression tester now, I am hoping to find a 90 degree elbow for it so I do not have to take the hood off.

Also, I just realized there was a 8n forum, sorry about posting in the wrong place.

I am waiting for a compression kit to arrive, I did skip over and confirm the wiring diagram, I did not get to test the resistor as my grandfather needed help.

So while there I checking the wiring, I grabbed a test light to verify power to the coil/dist and the damn thing fired up. Keep in mind, the last time it ran was when I initially posted, and the fuel is turned off. I guess I should let it run until it is empty.

all cylinders have around 100psi, what next?

I ordered a new fuel line, bowl and carb elbow strainer. The current fuel line dips above the fuel bowl, and at some point was fixed with a rubber bridge just before the carb elbow.

This turned out to be the resistor, replaced the bad resistor and the tractor starts up like a dream every time.

Thank you gentlemen!