9N Starting Trouble

[dgr146]

Hello. I am a newbie. This is only my second post;first about engine starting issues. I have been working on this tractor on and off since spring trying to get it to start and run consistently. Until now I have been able to research and follow along on others' posts about similar problems to mine for solutions, which has worked pretty well up until now. So now it's my turn to ask for guidance from the experts. The tractor is only used for occasional brush hogging a few acres of field, minor back blading to clean up snow and grading the driveway. Not heavy all day consistent use.

My tractor is a 1940 9N. Front mount dist/sqr coil and converted to 12 volts years ago by the previous owner. It has a Delco/Remy 3 wire alternator. Compression is 110 all four cylinders. My dad has owned the tractor for approx 25 years and really has done nothing other than fluid changes and spark plugs during that time. I seem to have inherited this machine with a renewed interest to get it running tip top. The tractor is located at his cabin property so I do not have daily access to it to trouble shoot my issues. but, I've taken many pictures and notes that I am hoping will provide answers to any follow up trouble shooting questions you may have.
As I stated above- its converted to 12 volts- and it seems to be wired differently than the diagrams I have researched; such as a 3 wire ignition switch- has three wires attached, but top position doesn't seem to do anything. Middle key position is off. Bottom position is "run". It still uses the neutral safety push button switch. Also, the ballast resistor only uses the the top studs- bottom has no wires affixed. I've tried to make some logic to the wiring set up and its similar enough to published diagrams that its beginning to make sense. Following the wires is difficult at times do to years of paint build up, taped or wrapped wires, hidden areas, etc.. The tractor has run fine until the past few years or so- but here's the issues and what I've done to attempt to fix.

I noticed last winter it ran better with the choke pulled out a bit, but this problem got worse as time past. I removed air intake and realized it had been running (seemingly fine) on full choke! I rebuilt the carb, put in a Tractor Supply "tune up kit"- plugs(437's)/coil/condenser/points/cap/rotor.....All gaps proper -double checked. It ran fine for most of the spring/summer. It began to have starting issues again- mostly just when the engine was cold and would run and start fine when warm. I replaced the cap, rotor, points (.015)condenser,plugs (.025) and cleaned the carb again (M/S 241TSX). It seemed to run fine once started, but still hard starting. Ive read that most starting issues seem to be electrical and I'm focused on that issue. It has good compression and floods when it doesn't start- so I know its getting gas. This past weekend I replaced the ignition switch with another 3 wire identical to the old. I replaced the ammeter along with the ballast resistor (A8NN12250B) and the inline ceramic resistor (8NE10306)-.6 ohms- This resistor was actually cracked. I did this to eliminate potential electrical deficiency points. After all this, it would still just crank but not start- maybe a sputter here and there. I was frustrated by this point. More at my lack of knowledge and feeling like I was just guessing now and throwing money at it. I'm mechanically inclined and routinely work on snowmobiles, quads, cars etc,,, But lack tractor knowledge/experience and really do want to learn.....

I checked my spark by using a new 437 plug gapped at 1/4". It jumped the gap with a bright blue spark at each cylinder- I did not expect that and it made me more stumped. So then as an experiment, I jumped the two posts on the Ballast Resistor and it fired right up immediately -like it was fuel injected! I immediately removed the jumper (screw driver) and it continued to run great. It did this several times as I duplicated the process. Once it warmed up, I didn't need the jumper for it to fire right up. If it had blue sparkkies before jumping, why did jumping the posts make it fire up so instantaneously? I looked at the test plug and cranked while jumped and the blue didn't appear any brighter?!?
As an experiment, I then tried to bypass the fixed inline ceramic resistor to see if maybe that was the problem and not needed. I turned the key on and saw that the ballast resistor was glowing bright red hot!! So i immediately disconnected the jumper from the fixed resistor. I'd never seen that ballast glow like that. Was like a light bulb element! At this point I'm honestly considering installing a switched jumper wire to the ballast resistor to turn on only when starting. I know that can't be the right answer but I'm frustrated and it seemed to work fine...What am I missing?? Sorry for the novel........Thank you in advance, Dave

 

[Royse]

I'm not going to hazard a guess on the wiring without seeing
where its hooked up to, but I'm assuming from your description
that the coil wire does go through the resistors. That's good.

So, did you get a 12V coil or a 6V coil?
If you have a 12V coil you shouldn't need the ceramic resistor, or
you may need a different size especially if the coil was 6V before.
You would have to measure the resistance of it to know.

If you have a 6V coil you still have to measure the resistance
of the coil and the ceramic resistor then add the OEM
resistance to get the correct total resistance in the circuit.

For 12V you're looking for about 3.6~4 ohms resistance total
when hot. The OEM resistor changes resistance with heat starting
at about .3 and going up to 1.3/1.4 ohms when hot.
By doing so, it is essentially that bypass switch you mentioned.

And yes, it does get hot, it will burn your skin and smoke but it
shouldn't glow the way you were talking about "in an instant".

 

[dgr146]

Yes. the coil wire does run thru the resistors. I believe there is a 6 volt coil on the tractor now. I put that one on in the spring. thinking it was a 12 volt coil when I purchased it. But when measuring between the the top wire connector and pig tail I get like 1.5. I actually have a new coil that IS 12 volt. I forgot to mention that I first installed that this past weekend, but the tractor would not fire. Upon checking the top post and pigtail I get about 2.8-3 ohms, however when checking between the top post and flat spring contact, there is absolutely no reading at all. So I am assuming that means it is a bad coil and I was planning on returning it.
Any thoughts on the blue spark before and after jumping the ballast resistor posts, but only starting when jumped?
If the key is on and I touch the top post of the coil with my meter and the other to ground somewhere, should I get a voltage reading? If so, how much?
I have a not expensive, but better than harbor freight multimeter that I am using. I did try to use it to read the voltage at the battery terminals but the numbers were just wild and unreadable. Is that because of the digital meter and the points?

 

[Royse]

With the 12V coil you could try your test with jumping the
ceramic resistor again, it may just work fine as 2.8 from the
coil and 1.3 from the OEM resistor gets you to 4.1 ohms.

Top post on the coil should read battery voltage with the key
on and points open. With the points closed it will vary based
on what resistors are in the circuit.

If you are trying to read the battery voltage with the tractor
running, then yes an analog meter will work better.

Blue spark but not starting is the reason most guys recommend
using an adjustable air gap spark tester. More accurate than
an old plug. That's not to say an old plug doesn't work, only
that you can get a better measurement. This could be as
simple as the battery has gotten run down part way from all
the cranking, so now it will only start when you jumper it.
Have you recharged the battery?

 

[dgr146]

Thats a great point- No I did not recharge the battery and I remember checking the battery voltage with tractor off and it read something around 12.18-ish volts towards the end of working on it and many cranking sessions. I will pick up an air gap tester and a good analog meter before my next trip to the cabin, hopefully in a few weeks. And definitely recharge the battery first. Is the top coil post voltage check something I should be checking to make sure its getting full battery voltage and if so, how do you manually rotate to get the points open for that reading?
Another thing I just remembered I forgot to put in original post: I believe the first two sets of points were fried. The contact point attached to the adjusting bracket looked like a donut- it had a hole right thru the middle. It should be solid, no hole, correct??

 

[Royse]

I use a hand crank to rotate them. Oddly enough, one for a
Farmall Cub works fine and is usually easier to find.
But, you can hold the belt tight and rotate it with the fan.
Easier to do if you take the plugs out first.
May want to take them out and clean them anyway if flooded.

Points can be "ventilated" with a hole through them.
Most good ones are and some of the cheaper ones too.
Look for pitting and transfer of metal from one contact to the
other as well as wear down on the rubbing block. If that rubbing
block is plastic where it rides on the cam lobes it will wear quickly.

 

[dgr146]

Thanks for the tips and advice. Hopefully I can get back to look at it again in the next few weeks.......