Intermittent Spark 8N

My dads 8n, stopped running this summer, I finally had time to look about it. It's a 6v system, side mount dis. I'm getting an intermittent spark on at least one of the spark plugs now. I cleaned the points, everything there looks ok, unless I've missed something, I need to still check the gap. I have power to the coil and Dis. I checked the coil and I'm getting 1.2 ohm.

Thats as far as I've gotten so far, anything else to check? I'm going to pick up a condenser since they are cheap and from what I've read a coil as well since this one checks at 1.2.

Thanks in advance.

I wouldn't buy anything just yet. Round can coils are just about
bullet proof and condensers rarely fail. Check the point gap on all
four lobes. Gap at .025, same as the plugs.
Clean the plugs with lacquer thinner or a propane torch.
Clean the points with spray electrical cleaner and/or a piece of
brown paper bag. They corrode when left setting.

Why are you replacing parts that are not defective?

Troubleshoot the problem before you buy parts.

How did you clean the points?

Setting the gap, .025, would be the first thing you should do.


Confirm that you have 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.

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. J


Post back w/ results; I'll be interested in what the problem was.
75 Tips

When i first checked for spark I didn't have anything. So I dressed the points with some card stock. I did not clean them with contact cleaner. The "spinny" thing under the cap had some greyish black crusty stuff on the end that touches the four points on the spark plug wires, I gently cleaned that off. With those two Items done I was getting the intermittent spark.

I have continuity from the power wire on the side of the dis to the end of the points. and across the points when they are closed. I did not check voltage across them when closed.

I was going to get a coil, cause I thought those were supposed to read 2.2 ohm across the two posts?

Also, I'm going to check the fuel flow like has been talked about here as well, I suspect I might have two issues.

" I did not check voltage across them when closed. "

Check voltage across the open points. That's important.

" I thought those were supposed to read 2.2 ohm across the two posts"

Usually about 2 ohms or so, but 1.2 could just be your technique or the meter. Not worth replacing a coil over anyway. Just turn the engine over and see if you get the spark to jump 1/4".

Remember, the number 1 cause of a weak spark is a weak battery. Put it on a charger (tip # 60).
75 Tips

Ok, let me do some more checking. I'll grab a can of contact cleaner and do some looking.

Thanks, I'll let you know what happens.

My points cleaner is a piece of fine sandpaper :shock: I am not going to chase my tail all day over a dirty set of points. They are sacrificial and can be replaced once they are eliminated as the issue if not they can still be replaced... Its a no brainier to me I am not out to salvage every set of points I come into contact with.

Open line voltage does not mean much to me and that's the number one reason no start no crank issues go on for page after page until they get lucky and find the source of the voltage loss/drop. The correct way to test voltage is to put load on front of voltage. It should read like this...

Check loaded voltage across the open points. That's important.

Ones loaded voltage is eliminated you can move on till its not eliminated its a prime suspects.

Any voltage check of the ignition system should read loaded voltage not voltage, open line voltage is a ghost and will eat your lunch. It will eat the best lunch you can bank on that.

(quoted from post at 06:41:26 12/09/17)
My points cleaner is a piece of fine sandpaper :shock: I am not going to chase my tail all day over a dirty set of points. They are sacrificial and can be replaced once they are eliminated as the issue if not they can still be replaced... Its a no brainier to me I am not out to salvage every set of points I come into contact with.

Open line voltage does not mean much to me and that's the number one reason no start no crank issues go on for page after page until they get lucky and find the source of the voltage loss/drop. The correct way to test voltage is to put load on front of voltage. It should read like this...

Check loaded voltage across the open points. That's important.

Ones loaded voltage is eliminated you can move on till its not eliminated its a prime suspects.

Any voltage check of the ignition system should read loaded voltage not voltage, open line voltage is a ghost and will eat your lunch. It will eat the best lunch you can bank on that.

Click to expand...

I checked the voltage with the points open or as close as I can get to top of the lobe and I'm getting 6.22, basically what the battery has in it currently without charging it.

I cleaned the rotor (had a decent amount of carbon on it) and the points. I have not checked the gap on the points or spark plugs yet though.

I took the plug wire off the top of the Dist cap from the coil and I have good spark that will jump .25 inch.

Plus, I drained the gas tank, cleaned the screen in the elbow. I'm replacing the screen/gasket in the bowl and I need to pull the shut off valve yet to check the screen in the tank while its empty.

Ran out of time for everything else.

If you are sure you are get'N spark that will jump at the minimum of 1/4 spark is notcher problem...

Back to your points open voltage check it don't mean chit its still a open circuit a load needs to be applied to the ignition source a volt meter is not a load....

Reread

It should read like this...

Check """"loaded"""" voltage across the open points. That's important.

I use a headlight bulb (3 to 4 amps load) any bulb that would pull at the least a amp will do it like a 1156 parking lamp bulb....

Bulb Number-----Filament Amps
1156--------------------------2 amps

Big update.

Tractor starts and runs now, but it has a slight issue yet. It starts easy, sometimes needs a quick pull of the choke. But it will run maybe for 5 minutes, 1 minute or 20 minutes, then cut out and either die completely or almost die and then take back off again. I still think its a spark issue and not a fuel issue.

Once it dies it starts right back up. I was watching the amp meter once when it cut off and it dropped to -10 then back to zero, it was around +10 when I had it close to half throttle.

Reason, I think its spark related yet is when I was checking for spark the last time before it fired up, I wasn't getting any spark. Then boom I had spark and it tried to start. I put the plug back in and it fired up.

So still trouble shooting, but farther than before since it runs and sounds good.

(quoted from post at 16:11:04 12/11/17)

(quoted from post at 06:41:26 12/09/17)
My points cleaner is a piece of fine sandpaper :shock: I am not going to chase my tail all day over a dirty set of points. They are sacrificial and can be replaced once they are eliminated as the issue if not they can still be replaced... Its a no brainier to me I am not out to salvage every set of points I come into contact with.

Open line voltage does not mean much to me and that's the number one reason no start no crank issues go on for page after page until they get lucky and find the source of the voltage loss/drop. The correct way to test voltage is to put load on front of voltage. It should read like this...

Check loaded voltage across the open points. That's important.

Ones loaded voltage is eliminated you can move on till its not eliminated its a prime suspects.

Any voltage check of the ignition system should read loaded voltage not voltage, open line voltage is a ghost and will eat your lunch. It will eat the best lunch you can bank on that.

Click to expand...

I checked the voltage with the points open or as close as I can get to top of the lobe and I'm getting 6.22, basically what the battery has in it currently without charging it.

I cleaned the rotor (had a decent amount of carbon on it) and the points. I have not checked the gap on the points or spark plugs yet though.

I took the plug wire off the top of the Dist cap from the coil and I have good spark that will jump .25 inch.

Plus, I drained the gas tank, cleaned the screen in the elbow. I'm replacing the screen/gasket in the bowl and I need to pull the shut off valve yet to check the screen in the tank while its empty.

Ran out of time for everything else.

Click to expand...

Hi

You said:
"I was watching the amp meter once when it cut off and it dropped to -10 then back to zero, it was around +10 when I had it close to half throttle."

You have an intermittent short somewhere in the wiring. When the short "makes" it grounds out the system and kills the power to the ignition which kills the motor. You can check the whole wiring harness for chaffed insulation that could be rubbing against the engine, hood, or anything grounded, or you could narrow it down to a particular circuit first by disconnecting one circuit at a time until the problem goes away. For example if the tractor has lights, disconnect the wire that feeds the light switch from the terminal block. If the problem goes away it is in the lighting circuit. If it still has the problem, disconnect the wire from the voltage regulator to the terminal block. If the problem goes away, the short is in the generator/regulator circuit. If it still has the problem then it is in the ignition circuit.

later
deano

(quoted from post at 19:33:58 12/14/17) Hi

You said:
"I was watching the amp meter once when it cut off and it dropped to -10 then back to zero, it was around +10 when I had it close to half throttle."

You have an intermittent short somewhere in the wiring. When the short "makes" it grounds out the system and kills the power to the ignition which kills the motor. You can check the whole wiring harness for chaffed insulation that could be rubbing against the engine, hood, or anything grounded, or you could narrow it down to a particular circuit first by disconnecting one circuit at a time until the problem goes away. For example if the tractor has lights, disconnect the wire that feeds the light switch from the terminal block. If the problem goes away it is in the lighting circuit. If it still has the problem, disconnect the wire from the voltage regulator to the terminal block. If the problem goes away, the short is in the generator/regulator circuit. If it still has the problem then it is in the ignition circuit.

later
deano

Click to expand...

Figured as much, Thought I got lucky when I got it run. I will do this next week when I get some more time.

Thanks,

(quoted from post at 13:59:16 12/15/17)

(quoted from post at 19:33:58 12/14/17) Hi

You said:
"I was watching the amp meter once when it cut off and it dropped to -10 then back to zero, it was around +10 when I had it close to half throttle."

You have an intermittent short somewhere in the wiring. When the short "makes" it grounds out the system and kills the power to the ignition which kills the motor. You can check the whole wiring harness for chaffed insulation that could be rubbing against the engine, hood, or anything grounded, or you could narrow it down to a particular circuit first by disconnecting one circuit at a time until the problem goes away. For example if the tractor has lights, disconnect the wire that feeds the light switch from the terminal block. If the problem goes away it is in the lighting circuit. If it still has the problem, disconnect the wire from the voltage regulator to the terminal block. If the problem goes away, the short is in the generator/regulator circuit. If it still has the problem then it is in the ignition circuit.

later
deano

Click to expand...

Figured as much, Thought I got lucky when I got it run. I will do this next week when I get some more time.

Thanks,

Click to expand...

Hi guys,

Got the tractor running again sort of. I wanted to ask a carburetor question before I pulled it off for a good cleaning. It takes a puff of starting fluid to get it to start. Once started it will run for awhile then die. It will restart with the choke, does not need starting fluid after it has started the first time. But, at half throttle I have to feather the choke to keep it from dyeing, at 1/3 throttle I don't need as much choke to keep it running.

Could this be an adjustment issue or the carb needing cleaned again?

Thanks,

"Could this be an adjustment issue or the carb needing cleaned again?"

Theoretically could be either. Where are your adjustments set?
Have you checked fuel flow through the carb?
Remove the drain plug, then turn the fuel on and use a clear jar to catch the fuel.
Should run a pint in less than two minutes in a fairly steady stream.
The clear jar will let you inspect the fuel for dirt and/or water.
If that's good, the carb may need to be disassembled and cleaned.

(quoted from post at 17:40:48 08/13/18) "Could this be an adjustment issue or the carb needing cleaned again?"

Theoretically could be either. Where are your adjustments set?
Have you checked fuel flow through the carb?
Remove the drain plug, then turn the fuel on and use a clear jar to catch the fuel.
Should run a pint in less than two minutes in a fairly steady stream.
The clear jar will let you inspect the fuel for dirt and/or water.
If that's good, the carb may need to be disassembled and cleaned.

Click to expand...

Thanks,

I pulled the plug on the carb just enough to see if I had a decent amount coming out, but I'll get a jar and time it. Fuel bowl and screen were cleaned a few months ago when I was having some spark issues.

I can't remember how I had it set, I had found a write up on how to adjust the carb. I thought it was on this forum, but I can't seem to find it now.

I'm gonna pick up a bucket of the regular carburetor cleaner at the farm store in case I need to pull it and clean it.

[b:1c99190911][i:1c99190911]

Try this, for settings on your MS Carb.


GB[/i:1c99190911][/b:1c99190911]

Ok, I soaked and cleaned the carb. Adjusted it as that said to, it runs good at 1/3 throttle on up and doesn't seem to want to cut out and stall like before. But it won't idle at all and if I drive it around it wants to stall bad while driving, now I can keep it going by feathering the choke.

Someone had mentioned the fuel flow, I had cleaned the screen in the fuel tank, a new screen in the fuel bowl and the screen in the elbow at the carb is clean. I didn't have a glass jar like suggested but I pul a coffee can under it and took out the main plug out and I get a good flow until the bowl drains, from then to its not a steady stream, more of a fast drip. Does that sound right? To fill a glass jar in 2 minutes seems like a stretch for this.

I'll do some more research and fiddle with it when I get time. The only other thing would be the fuel line from the tank down or an issue in the carb?

fast drip is not good. that's why u need to feather the choke. how much gas is in your tank? it you're down to an inch or less, you're in reserve pickup territory, and the reserve is often plugged. how do u open the fuel shutoff? a couple of turns? all the way?

here's an easy test - if you're low, pour another 2 gallons in and see what happens.

(quoted from post at 17:01:39 08/29/18)
fast drip is not good. that's why u need to feather the choke. how much gas is in your tank? it you're down to an inch or less, you're in reserve pickup territory, and the reserve is often plugged. how do u open the fuel shutoff? a couple of turns? all the way?

here's an easy test - if you're low, pour another 2 gallons in and see what happens.

Click to expand...

Good point, its not full by any means but I put some in when I had it outside. Not sure how much.

I open it more than a few turns. I'll play with it a bit now that I know there is an issue.