No Spark on 8n

[kyford8n]

Hey guys I have a problem I can’t seem to resolve.

A couple of weeks ago I rebuilt my carb and had tractor running great. Did not start it for a couple of weeks. Went out yesterday to clear some snow off and could not get it to start.

I thought I just flooded it because I had gas dripping out of tube going to air cleaner. Took carb off to be sure float wasn’t sticking and put everything back together only to get same results. Checked spark and did not have any. I have checked the following:

1. Have power going to coil.
2. Don’t seem to have power between coil and distributor. (Side mount).
3. Decided to replace points, condenser, rotor, distributor cap. Still no spark
4. Checked on/off switch to be sure it was getting power and it was.

I am thinking I need to replace coil now but not sure if I am missing something else.

Not sure why it ran so good and now mining just by sitting for 2 weeks. Any help would be appreciated

 

[Bruce (VA)]

Don?t guess at the cause of the problem; guessing can get expensive. And leave you breathless chasing every guess.......it could be this, it could be that......just troubleshoot the problem and leave the guess work for buying Lottery tickets.

Do not buy a new part for the tractor until you can answer this question: how do I know the part on the tractor is defective? Your coil didn't go bad from sitting too long.

You've started the troubleshooting correctly; keep at it.

Confirm that you have the correct voltage to the coil. Battery voltage, points open. About half that if the points are closed.

Do you have battery voltage across the points when they are open? (with the points open, put one probe on one side of the points & the other probe on the opposite side of the points) Verify the gap on the points at .025. Then, dress the points by running a piece of card stock or brown paper bag through them. New points sometimes have an anti-corrosive dielectric coating on them & old points can corrode or pick up grease from a dirty feeler gauge or excessive cam lubricant. (I always spray my feeler gauge blade off w/ contact cleaner.) Make sure you have voltage across the points, as in past the insulator on the side of the distributor. That is a very common failure point on sidemounts, along w/ the attached copper strip. It's hard to find a short there because it is usually an intermittent . So 'wiggle' the insulator & the copper strip a bit when you are doing your checking. If you find the short there, the Master Parts catalog lists everything you need on page 154. You can make the strip and you could also make the insulators as well. But, somethings are just easier & in the long run cheaper to buy. Get the strip, 12209, screw 350032-S, 12233 bushing & 12234 insulator & just replace it all.


If you just replaced the rotor & lost spark, put the old one back in. Insure that the rotor fits firmly on the shaft & that the little clip is there. Make sure the distributor cap is not cracked, doesn?t have gouges in it from the rotor or brass shavings & doesn't have carbon tracks. Check continuity on the secondary coil wire. Make sure it is firmly seated in both the cap & the coil. Next, remove the secondary coil wire from the center of the distributor cap, turn the key on & crank the engine while holding the end of the wire 1/4" from a rust & paint free spot on the engine. You should see & hear a nice blue/white spark. If not, you have a bad coil or condenser. Just put the old condenser back in to eliminate that as a possibility.

Post back w/ results; I'll be interested in what the problem was.
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[kyford8n]

Thanks Bruce

I tried to check for spark with the center spark plug wire on the distributor and did not get spark. I also tried between points and did not get a reading there either.

All the parts I replaced were parts that I had bought some time back and never got around to changing. It the issue I am having were before I replaced any of the parts.

I am stuck, unless it is the coil?

 

[Bruce (VA)]

" I also tried between points and did not get a reading there either."

Well, that tells me it's NOT the coil.

You have 2 circuits in the distributor. Primary & secondary. In order for the secondary circuit (the coil) to work, you need current to the primary circuit. You do not have current to the primary circuit so do not bother trying to test the secondary circuit.

Get out your digital volt meter.

With the points open, key on, tell me the voltage at:

The plus side of the coil.

The negative side of the coil.

The stud on the side of the distributor.

Across the open points.

Post back w/ that info.
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[kyford8n]

Get out your digital volt meter.

With the points open, key on, tell me the voltage at:

The plus side of the coil.- 12.6

The negative side of the coil. 0

The stud on the side of the distributor. 0

 

[Bruce (VA)]

" The negative side of the coil. 0 "

Wow!

First defective round coil I've run into in a long time.

Leave the key on?

Just for grins, measure the resistance between the plus side of the coil and the center conductor. Probably a dead short or open.

Go to NAPA, get p/n IC14SB. 12 volt coil, no external resistor needed.
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[kyford8n]

Hey Bruce

I did some more trouble shooting this acternoon. Instead of a multimeter I used a light up continuity tester.

With key on and hooked to the negative battery ground. I tested the following sucessfully:

Positive side of coil- lit up
Negative side of. Oil- lit up
Post on distributor Lit up.
Also while hooked on the distributor I hit the push button start and light blinked on/off.
I also checked both sides of key and both lit up.

However, still no spark at plugs.
I checked copper strip inside of distributor and it was intact/tight
Gap Is set at .025

I don’t know what else to check

 

[Bruce (VA)]

Earlier you said " The negative side of the coil. 0 "

Well, if your meter reads correctly, you do not have battery voltage going to the distributor.

But, the light says you have voltage. The fact that it blinks says the points are opening and closing.

So, go back to your meter and switch to a lower scale to check the voltage on the distributor side of the coil.

Enough voltage to make a light blink but not power the coil is my thinking.
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[kyford8n]

I am officially confused.

I checked the positive side of coil with post on distributor and got a reading this time of 12.3ish. I also checked the positive post of coil with plug wire connecting the coil to distributor and got a reading there as well. I also checked the positive post of coil with plug wire connecting coil with distributor with the continuity light tester and the light was more dull than any of the other reading I took with it.

Any ideas??

 

[Bruce (VA)]

Well, that now makes 2 of us that are confused.

Sunday, you said:

" The plus side of the coil.- 12.6

The negative side of the coil. 0

The stud on the side of the distributor. 0 "

That means you have no voltage to the distributor. You have voltage to the coil, but not to the distributor based upon those readings.

Is that what you see now, or something different?
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[kyford8n]

That is correct, I was not able to getting any readings Sunday except at the positive side of coil.

I am now getting readings in the spots I wasn't on Sunday but still no spark at spark plugs.

I cant figure it out.

 

[Bruce (VA)]

What do you get at :

The stud on the side of the distributor.

Across the open points.
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[kyford8n]

I have not checked that yet.
It would be switch on, one teste leg on the stud on the side and the other leg across the points while they are closed correct?

 

[Bruce (VA)]

No.

That's two tests you need to do.

Side of the distributor, the stud, to ground. Points open, you should see battery voltage.

Then, check for the same voltage across the open points.
75 Tips

 

[kyford8n]

No.

That's two tests you need to do.

Side of the distributor, the stud, to ground. Points open, you should see battery voltage. [b:b549a839f3][u:b549a839f3][color=darkred:b549a839f3]Last night I was getting 12.4ish[/color:b549a839f3][/u:b549a839f3]
[/b:b549a839f3]
Then, check for the same voltage across the open points. [color=darkred:b549a839f3][b:b549a839f3][u:b549a839f3]I will need to re-check that when I get home this afternoon.[/u:b549a839f3][/b:b549a839f3][/color:b549a839f3][/color][/u]

 

[Bruce (VA)]

(quoted from post at 11:17:55 01/17/18) No.

That's two tests you need to do.

Side of the distributor, the stud, to ground. Points open, you should see battery voltage. [b:ea43e8f249][u:ea43e8f249][color=darkred:ea43e8f249]Last night I was getting 12.4ish[/color:ea43e8f249][/u:ea43e8f249]
[/b:ea43e8f249]
Then, check for the same voltage across the open points. [color=darkred:ea43e8f249][b:ea43e8f249][u:ea43e8f249]I will need to re-check that when I get home this afternoon.[/u:ea43e8f249][/b:ea43e8f249][/color:ea43e8f249][/color][/u]

Yep. Power to the stud does not mean power to the points.

 

[kyford8n]

Bruce,

I would like to start off by saying thank you for all your help. You have taught me a lot as I am new to tractors.

When I got home I started rechecking reading from the previous day. Some of the readings I was getting the day before were not reading last night.

My father in law had an old coil left over from an 8n he used to own and gave it to me. I pulled my coil off, wired up the one he gave me and starting checking readings again. Everything was getting power. Buttoned everything up, checked for spark at plugs and bingo, I finally had the spark I was looking for.

Attempted to start tractor and she fired right up in 8 degree temps after sitting idle for 3 weeks.

Very happy,
Thank you again for all your help.

 

[Bruce (VA)]

You're welcome. Glad to help.

And it's a rare occasion that a round coil fails cold, so I'm glad your persistence paid off.
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