Bruce (VA)
Well-known Member
" Is the coil bad? "
Probably not.
Coil problems are difficult to diagnose. For starters, round coils are pretty robust & square coils aren’t (because of the difference in insulation used), but neither one will hold up to a poorly done 12v conversion that allows too much current to the coil or leaving the key on (see tip # 38). Too much current creates heat which melts the insulation. Insufficient resistance in a 12v conversion will do the same thing. Rarely do coils just “go bad.”
There are a few ways to see if a coil is bad, but it’s not possible to determine if a coil is good w/o some expensive testing equipment. If you detect a dead short or high resistance in the coil w/ an ohm meter, it’s bad. If it’s cracked, it’s bad. If a sidemount coil w/ battery voltage to the primary will not jump a ¼” gap from the secondary wire to the block, it’s bad. But, here is the hard part: even if you do not detect a short, even if it will produce a spark, even if it’s not cracked, that doesn’t mean the coil will work when it’s hot & under a load. So, it’s a process of elimination. If the tractor starts & runs fine for 30 minutes or an hour then cuts off & refuses to re-start, and you checked for spark at the plugs & it had no spark at all, AND you have the correct voltage at the coil that’s a good sign that you have a bad coil. Let it cool off, restart it & if you have a good spark, odds are it’s a bad coil. But, even then, you might end up w/ a spare coil on the shelf!
Bottom line.......coils do go bad, but I'll venture a guess that 75% of new N coils sold today are sold to folks who do not understand how to diagnose a poor spark problem or how a coil works. So, for those who don’t know any better, in a no spark situation the first suspect is usually the coil……and, more often than not, it isn’t the problem.
Or as one regular around here humorously suggested: "Well, it is like this...I don't know or really understand what that black thing does & I am suspicious of the unknown, so I think the problem is the black thing."
First, charge the battery. (see tip # 60) . A weak battery gets you a weak spark. Or no spark.
Do you have battery voltage across the points when they are open? 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 guage 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 carbon tracks. Check continuity on the secondary coil wire. Make sure it is firmly seated in both the cap & the coil. In fact, replace it temporarily w/ a plug wire. 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.
75 Tips
Probably not.
Coil problems are difficult to diagnose. For starters, round coils are pretty robust & square coils aren’t (because of the difference in insulation used), but neither one will hold up to a poorly done 12v conversion that allows too much current to the coil or leaving the key on (see tip # 38). Too much current creates heat which melts the insulation. Insufficient resistance in a 12v conversion will do the same thing. Rarely do coils just “go bad.”
There are a few ways to see if a coil is bad, but it’s not possible to determine if a coil is good w/o some expensive testing equipment. If you detect a dead short or high resistance in the coil w/ an ohm meter, it’s bad. If it’s cracked, it’s bad. If a sidemount coil w/ battery voltage to the primary will not jump a ¼” gap from the secondary wire to the block, it’s bad. But, here is the hard part: even if you do not detect a short, even if it will produce a spark, even if it’s not cracked, that doesn’t mean the coil will work when it’s hot & under a load. So, it’s a process of elimination. If the tractor starts & runs fine for 30 minutes or an hour then cuts off & refuses to re-start, and you checked for spark at the plugs & it had no spark at all, AND you have the correct voltage at the coil that’s a good sign that you have a bad coil. Let it cool off, restart it & if you have a good spark, odds are it’s a bad coil. But, even then, you might end up w/ a spare coil on the shelf!
Bottom line.......coils do go bad, but I'll venture a guess that 75% of new N coils sold today are sold to folks who do not understand how to diagnose a poor spark problem or how a coil works. So, for those who don’t know any better, in a no spark situation the first suspect is usually the coil……and, more often than not, it isn’t the problem.
Or as one regular around here humorously suggested: "Well, it is like this...I don't know or really understand what that black thing does & I am suspicious of the unknown, so I think the problem is the black thing."
First, charge the battery. (see tip # 60) . A weak battery gets you a weak spark. Or no spark.
Do you have battery voltage across the points when they are open? 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 guage 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 carbon tracks. Check continuity on the secondary coil wire. Make sure it is firmly seated in both the cap & the coil. In fact, replace it temporarily w/ a plug wire. 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.
75 Tips
Bruce (VA)
Well-known Member
Bruce (VA)
Well-known Member
" How do I check for voltage across the points?"
When the points are open, the gap is .025. Put one probe of your meter on one side & the other probe on the other side. With the key on. You should see 6.35v or so.
" And how will I know if the copper strip and insulator are shorting? "
" .... 'wiggle' the insulator & the copper strip a bit when you are doing your checking."
If the voltage disappears then comes back as you wiggle the strip & insulator, it's shorted.
75 Tips
When the points are open, the gap is .025. Put one probe of your meter on one side & the other probe on the other side. With the key on. You should see 6.35v or so.
" And how will I know if the copper strip and insulator are shorting? "
" .... 'wiggle' the insulator & the copper strip a bit when you are doing your checking."
If the voltage disappears then comes back as you wiggle the strip & insulator, it's shorted.
75 Tips
Bruce (VA)
Well-known Member
Bruce (VA)
Well-known Member
There are 3 wires on the coil.
The secondary wire carries spark voltage to the plugs when the points open. It goes from the center of the coil to the center of the distributor cap. There is nothing you can measure there.
The other two wires are the primary circuit & carry battery voltage to the coil & then to the points.
Find the wire going from the side of the coil TO the side of the distributor. Turn the key on. You should see battery voltage there w/ the points open.
The secondary wire carries spark voltage to the plugs when the points open. It goes from the center of the coil to the center of the distributor cap. There is nothing you can measure there.
The other two wires are the primary circuit & carry battery voltage to the coil & then to the points.
Find the wire going from the side of the coil TO the side of the distributor. Turn the key on. You should see battery voltage there w/ the points open.
Bruce (VA)
Well-known Member
I tried taking off the rotor in the off chance that the clip was gone and it wasn't. So I tried putting the cap on there without the rotor and it still rock back and forth without the rotor in place. It wont even seat correctly.
Back in the fall, the distributor did jam and the entire housing spun and the oiler lodged in the side of the coil. That is why there is a new coil being put on and I assume that the housing of the distributor may have bent then.
Remarkably, no gears were shredded or broken because as the distributor spun, it broke one of the primary wires so the tractor stopped dead in its tracks.
To dislodge all of this, I had to completely remove the distributor to turn it back around and pull the oiler out of the coil.
It is quite the mess!
Back in the fall, the distributor did jam and the entire housing spun and the oiler lodged in the side of the coil. That is why there is a new coil being put on and I assume that the housing of the distributor may have bent then.
Remarkably, no gears were shredded or broken because as the distributor spun, it broke one of the primary wires so the tractor stopped dead in its tracks.
To dislodge all of this, I had to completely remove the distributor to turn it back around and pull the oiler out of the coil.
It is quite the mess!
Bruce (VA)
Well-known Member
" Bit I still have no spark"
That was a pretty long list of things I sent you to check out. Have you done that?
What was the voltage reading across the open points?
Tell us how you are checking for spark. Are you using an old plug w/ the gp open 1/4", or a plug checker?
Some folks think that checking for spark means pulling a plug wire off & looking for one. Well, it's the distance the spark jumps at the plug that gives you the info you want. It takes about 17kv to jump a 3/16" gap & 22kv to jump ¼” in the open air. Remember, it’s 14psi outside of the engine & about 90psi at a 6:1 compression ratio in the cylinders & compressed air creates electrical resistance, so you really need the 17-22kv to fire the plugs when the engine is running. A store bought plug checker will work better than an old plug because it won’t shock the snot out of you like an old plug might!
75 Tips
That was a pretty long list of things I sent you to check out. Have you done that?
What was the voltage reading across the open points?
Tell us how you are checking for spark. Are you using an old plug w/ the gp open 1/4", or a plug checker?
Some folks think that checking for spark means pulling a plug wire off & looking for one. Well, it's the distance the spark jumps at the plug that gives you the info you want. It takes about 17kv to jump a 3/16" gap & 22kv to jump ¼” in the open air. Remember, it’s 14psi outside of the engine & about 90psi at a 6:1 compression ratio in the cylinders & compressed air creates electrical resistance, so you really need the 17-22kv to fire the plugs when the engine is running. A store bought plug checker will work better than an old plug because it won’t shock the snot out of you like an old plug might!
75 Tips
.............and from yesterday, "
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PostPosted: Thu Mar 20, 2014 12:58 pm Post subject: Re: 8N No Spark Reply to specific post Reply with quote
Gotcha. And I do and the spark does jump."
OK, so which is it, "There is no spark at 1/4 inch specified." or "And I do and the spark does jump."???
ot a lot of possibilities between wire between coil & center of distributor cap and the plugs.......cap, rotor, 4 plug wires. That is only 6 items to verify. Get after it.
OOPS! I missed your "primary" comment. "No spark at the plugs but there is at the primary wire". What does that mean, i.e., "spark at primary wire"?
Bruce (VA)
Well-known Member
" I have no way for me to check the voltage across the points because the only thing I have is a test light. "
Well, that does make it a bit difficult to check the voltage.
" Is there any other way I can check them?"
Yes, you can use your light to see if you have ANY voltage across the points. And if the light goes out when you wiggle the insulator, that will tell you the insulator is shorted.
But the bigger question is why are you working with one hand behind your back? A cheap multi-meter goes for $10. You wouldn't plan on working on that tractor w/ a tool set that consisted of 2 screw drivers & a crescent wrench would you?
Basic sockets, wrenches, etc, a test meter & manuals are the bare minimum any old tractor owner should have.
Well, that does make it a bit difficult to check the voltage.
" Is there any other way I can check them?"
Yes, you can use your light to see if you have ANY voltage across the points. And if the light goes out when you wiggle the insulator, that will tell you the insulator is shorted.
But the bigger question is why are you working with one hand behind your back? A cheap multi-meter goes for $10. You wouldn't plan on working on that tractor w/ a tool set that consisted of 2 screw drivers & a crescent wrench would you?
Basic sockets, wrenches, etc, a test meter & manuals are the bare minimum any old tractor owner should have.
The wire leading from the coil to the side of the distributor has spark. However there is nothing coming through the cap. I pulled the sparkie wires off and hooked each of them into the top of the coil and connected a test light to the end. All had spark. When I put them back onto the cap, they have no spark.
What we have here is a failure to communicate. Having a low voltage that will light your test light is not a "spark" in my mind or many other minds. We would call "voltage present" if light illuminates on the primary.
Don't use a light on the secondary......use a gap to see if a spark will jump the gap. Now, with wire plugged into the center tower of the coil & the other end placed 1/8 inch from engine metal parts, do you see a spark jump between the wire end & the metal of the engine? If yes, increase gap to 1/4 inch & repeat. Still see spark. This is enough spark that you can hear it! Ign must be on & starter engaged/spinning engine.
A serious spark.......simulating engine at speed:
Here I let arc go to a primary terminal, but it would be same if arcing to engine metal parts.http://s192.photobucket.com/user/JMOR_photo/media/Ign/MVI_0196.mp4.html?sort=3&o=46
K. Take distributor cap off for access to points. Bump starter until points are open. Turn on key & use screwdriver to short across open point gap. Look carefully for a spark at screwdriver......it will be quite small compared to secondary spark. During this time did coil still get hot?
Bruce (VA)
Well-known Member
" There was a spark although it only happened about 50% of the time, meaning sometimes there was a spark, sometimes there wasn't"
There two possibilities why that is occurring, both of which I've already addressed:
" First, charge the battery. (see tip # 60) . A weak battery gets you a weak spark. Or no spark."
" So 'wiggle' the insulator & the copper strip a bit when you are doing your checking. "
So, have you charged the battery? Have you checked the insulator & copper strip for a short?
And, does your test light come on across the open points?
There two possibilities why that is occurring, both of which I've already addressed:
" First, charge the battery. (see tip # 60) . A weak battery gets you a weak spark. Or no spark."
" So 'wiggle' the insulator & the copper strip a bit when you are doing your checking. "
So, have you charged the battery? Have you checked the insulator & copper strip for a short?
And, does your test light come on across the open points?
K, if the coil still got hot with points open, then the possibilities are the copper strip/insulator bushing that Bruce described or a shorted condenser. Easy to disconnect condenser & see if heating persists. Then disconnect the wire from coil to distributor feed-thru & surely heating will stop. Don't despair....we are nearly there.
Bruce and JMOR will get you fixed up.
They have said it, but I'll add again that
the #1 trouble spot on a side mount distributor
is the stud on the side of the distributor housing where the wire's current passes thru to and including the copper strip.
All of them and I stress all, will short here eventually.
A short there means no points spark and big heat in the coil when you turn the key on.
They have said it, but I'll add again that
the #1 trouble spot on a side mount distributor
is the stud on the side of the distributor housing where the wire's current passes thru to and including the copper strip.
All of them and I stress all, will short here eventually.
A short there means no points spark and big heat in the coil when you turn the key on.
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