Bill in ark
Member
Is there a sure way to test a 9n coil without fancy tools?
How about test a condenser?
How about test a condenser?
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- Thread starter Bill in ark
- Start date
Toward the end of my ownership of my 9N, I got tired of that front coil and resistor combo and replaced it with a coil and condenser that is used on the late 8Ns. A fairly simple conversion. Never had to worry again. It always started and ran well. My model A and AA truck were wired that way and always started and ran well.
Tom in St. Louis
Member
I am having a similar issue with my 52 8N. Not getting a spark at the plug.
I have been trying to get the specs on my coil so I could check it. So far, I have been able to get some general specs.
The primary windings on the coil (the two small terminals) should have a resistance of 0.4 to 2 ohms. The resistance between the secondary windings (the big terminal in the middle of the coil) and either of the primary terminals should be between 6k and 20k ohms. These are general numbers.
I took my condenser to the local O'Reilly store and asked if it could be checked. The manager said no because they are so cheap, like $10. You can try a new condenser, but there is no guarantee they are good.
Hope this helps. Good luck.
I have been trying to get the specs on my coil so I could check it. So far, I have been able to get some general specs.
The primary windings on the coil (the two small terminals) should have a resistance of 0.4 to 2 ohms. The resistance between the secondary windings (the big terminal in the middle of the coil) and either of the primary terminals should be between 6k and 20k ohms. These are general numbers.
I took my condenser to the local O'Reilly store and asked if it could be checked. The manager said no because they are so cheap, like $10. You can try a new condenser, but there is no guarantee they are good.
Hope this helps. Good luck.
(quoted from post at 10:52:29 09/17/16) Is there a sure way to test a 9n coil without fancy tools?
How about test a condenser?
Connect a test light between the battery and the terminal on top of the coil (with the coil installed on the dist.) DO NOT turn the switch on, crank the engine, if the light flashes the path through the points is good and the coil is probably bad, if it stays on steady you have a short in the distributor, if it doesn't light at all your points are probably bad or the pig tail on the bottom of the coil is not making contact. Yes you can test a condenser too but it's very likely good.
Bruce (VA)
Well-known Member
You got the correct & short answer from R. Geiger.
Now for the explanation.
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 ?? 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."
So, what problem are you having that leads you to suspect a coil or condenser failure?
Post back w/ the symptoms & you will get plenty of help,
75 Tips
Now for the explanation.
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 ?? 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."
So, what problem are you having that leads you to suspect a coil or condenser failure?
Post back w/ the symptoms & you will get plenty of help,
75 Tips
Bruce (VA)
Well-known Member
Bruce (VA)
Well-known Member
That's exactly what I did with my 1950 MG-TD.
It was either the coil or condenser and I had spares for both but no time to check both. Replaced them and the car runs fine. Put the coil on the 740. It runs fine. The condenser checked out fine on the meter (as most do) but it's clearly bad.
It was either the coil or condenser and I had spares for both but no time to check both. Replaced them and the car runs fine. Put the coil on the 740. It runs fine. The condenser checked out fine on the meter (as most do) but it's clearly bad.
Tom in St. Louis
Member
Bruce,
On my 52 8N which was converted to 12 volt, negative ground, I measure 12 volts across the open points.
I am not clear on which insulator and copper strip you are talking about. Thanks.
On my 52 8N which was converted to 12 volt, negative ground, I measure 12 volts across the open points.
I am not clear on which insulator and copper strip you are talking about. Thanks.
Tom in St. Louis
Member
My 8N has a side mount distributor.
The secondary lead from the coil goes into the center of the distributor cap, then to a rotor under the cap. I don't think I have a copper wire to the distributor.
I have replaced the condenser twice, so that means it did not work with 3 different condensers.
I filed the contacts on the points yesterday to clean any corrosion, and set the the gap at 0.025".
I am using a spark plug tester, the kind that looks like a spark plug with an air gap that you clamp on to a ground.
The secondary lead from the coil goes into the center of the distributor cap, then to a rotor under the cap. I don't think I have a copper wire to the distributor.
I have replaced the condenser twice, so that means it did not work with 3 different condensers.
I filed the contacts on the points yesterday to clean any corrosion, and set the the gap at 0.025".
I am using a spark plug tester, the kind that looks like a spark plug with an air gap that you clamp on to a ground.
Bill in ark
Member
6.5 volts going into coil. Spark at the points. No spark at plugs. That's about it so far.
Bill in ark
Member
Don't have a spare coil.
Points at 15 and have good spark if jumped with a screwdriver.
6.5 volts going into coil but no spark at plugs.
Points at 15 and have good spark if jumped with a screwdriver.
6.5 volts going into coil but no spark at plugs.
Bruce (VA)
Well-known Member
Assuming that the bushings & advance weights are ok (*see below), & that you have correct voltage to the coil (battery voltage with the points open and about half that with the points closed), the problem is in the distributor.
Once you get the distributor on the bench, the first thing you need to check is bushing wear. If the shaft has any sideways movement AT ALL, the bushings must be replaced. (*** see below).
The most common electrical failure (no spark, weak spark) points on the front mount are:
1. The insulator under the brass concave head screw & where the copper strip attaches. (it?s fiber & will wear out; poke & prod w/ your meter leads to make sure it still works) If you need to replace the insulator, use a .250 x 3/8 nylon square nylon anchor nut available at most big box home stores
2. The pigtail at the bottom of the coil not making contact w/ the concave head brass screw inside the distributor. (With the coil on, the pigtail must firmly contact the brass screw. No contact = no spark
3. The copper strip is broken or grounded to the plate. (look very carefully for cracks & breaks).
4. The condenser wire grounding to the plate or side of the distributor.
5. The tab on the bottom of the coil not making contact w/ the brass button on the cap. (With the cap on, the tab must firmly contact the brass button. No contact = no spark.)
6. Incorrect positioning of the spring clip on the plate causing the pigtail to ground. (the open part of the clip goes between 7 & 9 o?clock on the plate. That puts the straight part of the clip opposite of the timing screw at 3 o?clock)
7. Incorrect seating of the coil on the distributor due to a loose bail or no gasket.(the coil must not move at all; if it does, replace the gasket or bail. Or stick some cardboard under the bail).
8. Water/moisture inside the cap due to gasket failure or the absence of a gasket. (the cap AND coil have gaskets)
9. Dirty/corroded/burned/incorrectly gapped or misaligned points. I use only Wells, Blue Streak or Echlin brand points (* *see below). If you are using quality points and cannot get the gap to open to .015, chances are you need to replace the bushings.
10. Burned rotor, cracked/carbon tracked cap.
After you find the problem & re-check the point gap, do a continuity check before you put the distributor back on the tractor. Before you start, make sure your meter/light works.
With the distributor still off the tractor, follow these steps:
1. Coil off, cap off, points open. One probe on the brass screw & the other on both sides of the open points. On the side closest to the cam, you should have continuity. Not on the other side! If you do, you will also have continuity everywhere because the points are grounded.
2. Coil off, cap off, points open. One probe on the brass screw & the other anywhere on the body of the distributor. You should have no continuity! Now, rotate the tang on the distributor....as the points open & close, you have continuity (closed) and lose it when they open.
3. Put the coil on the distributor, cap off, points open. One probe on the lead on the top of the coil, the other on the cam side of the open points. You should have continuity!
4. Coil on, cap off, points open. One probe on the lead on the top of the coil, the other anywhere on the body of the distributor. You should have no continuity!
At this point, I just put the distributor, coil & cap all back on the tractor as a unit. The reason I do this is because it is real easy to get the cap or coil misaligned trying to put it back together, one piece at a time. The result is something gets broken or you get a ?no spark? problem.
It's possible to put it back on wrong & break it. Look at the slot on the end of the cam shaft. Whatever angle it happens to be, turn the distributor tang to match it. Make sure you can tell the wide side from the narrow side on both the cam & distributor! (close counts). Place the distributor on the front of the engine, gently push it in place & slowly turn the distributor body until you feel the tang slip into the slot. Rotate the distributor body until the bolt holes line up. Hand tighten the two bolts until the distributor body is flush with the timing gear cover.
* Unscrew the plate hold down screw & remove the C clip to get the plate out. Remove the shaft & weights. The weights should freely move.
* *NAPA part numbers:
? Points: FD-6769X
? Condenser: FD-71
? Rotor: FD-104
? Cap: FD-126
*** There are three ways to replace the bushings in a front distributor:
1. Buy new bushings (part numbers 9N12120 front & 18-12132 rear). Press out the old ones, press in the new ones and ream to fit. CAUTION: do not try this unless you have a press & know how to use it. If you break the base, a new one costs $130. If you bend the tower which holds the front bushing, a new plate will cost you $30.
2. Take the new bushings and distributor to your local machine shop.
3. Send the distributor out for bushing replacement if you do not have a local machine shop.
75 Tips
Once you get the distributor on the bench, the first thing you need to check is bushing wear. If the shaft has any sideways movement AT ALL, the bushings must be replaced. (*** see below).
The most common electrical failure (no spark, weak spark) points on the front mount are:
1. The insulator under the brass concave head screw & where the copper strip attaches. (it?s fiber & will wear out; poke & prod w/ your meter leads to make sure it still works) If you need to replace the insulator, use a .250 x 3/8 nylon square nylon anchor nut available at most big box home stores
2. The pigtail at the bottom of the coil not making contact w/ the concave head brass screw inside the distributor. (With the coil on, the pigtail must firmly contact the brass screw. No contact = no spark
3. The copper strip is broken or grounded to the plate. (look very carefully for cracks & breaks).
4. The condenser wire grounding to the plate or side of the distributor.
5. The tab on the bottom of the coil not making contact w/ the brass button on the cap. (With the cap on, the tab must firmly contact the brass button. No contact = no spark.)
6. Incorrect positioning of the spring clip on the plate causing the pigtail to ground. (the open part of the clip goes between 7 & 9 o?clock on the plate. That puts the straight part of the clip opposite of the timing screw at 3 o?clock)
7. Incorrect seating of the coil on the distributor due to a loose bail or no gasket.(the coil must not move at all; if it does, replace the gasket or bail. Or stick some cardboard under the bail).
8. Water/moisture inside the cap due to gasket failure or the absence of a gasket. (the cap AND coil have gaskets)
9. Dirty/corroded/burned/incorrectly gapped or misaligned points. I use only Wells, Blue Streak or Echlin brand points (* *see below). If you are using quality points and cannot get the gap to open to .015, chances are you need to replace the bushings.
10. Burned rotor, cracked/carbon tracked cap.
After you find the problem & re-check the point gap, do a continuity check before you put the distributor back on the tractor. Before you start, make sure your meter/light works.
With the distributor still off the tractor, follow these steps:
1. Coil off, cap off, points open. One probe on the brass screw & the other on both sides of the open points. On the side closest to the cam, you should have continuity. Not on the other side! If you do, you will also have continuity everywhere because the points are grounded.
2. Coil off, cap off, points open. One probe on the brass screw & the other anywhere on the body of the distributor. You should have no continuity! Now, rotate the tang on the distributor....as the points open & close, you have continuity (closed) and lose it when they open.
3. Put the coil on the distributor, cap off, points open. One probe on the lead on the top of the coil, the other on the cam side of the open points. You should have continuity!
4. Coil on, cap off, points open. One probe on the lead on the top of the coil, the other anywhere on the body of the distributor. You should have no continuity!
At this point, I just put the distributor, coil & cap all back on the tractor as a unit. The reason I do this is because it is real easy to get the cap or coil misaligned trying to put it back together, one piece at a time. The result is something gets broken or you get a ?no spark? problem.
It's possible to put it back on wrong & break it. Look at the slot on the end of the cam shaft. Whatever angle it happens to be, turn the distributor tang to match it. Make sure you can tell the wide side from the narrow side on both the cam & distributor! (close counts). Place the distributor on the front of the engine, gently push it in place & slowly turn the distributor body until you feel the tang slip into the slot. Rotate the distributor body until the bolt holes line up. Hand tighten the two bolts until the distributor body is flush with the timing gear cover.
* Unscrew the plate hold down screw & remove the C clip to get the plate out. Remove the shaft & weights. The weights should freely move.
* *NAPA part numbers:
? Points: FD-6769X
? Condenser: FD-71
? Rotor: FD-104
? Cap: FD-126
*** There are three ways to replace the bushings in a front distributor:
1. Buy new bushings (part numbers 9N12120 front & 18-12132 rear). Press out the old ones, press in the new ones and ream to fit. CAUTION: do not try this unless you have a press & know how to use it. If you break the base, a new one costs $130. If you bend the tower which holds the front bushing, a new plate will cost you $30.
2. Take the new bushings and distributor to your local machine shop.
3. Send the distributor out for bushing replacement if you do not have a local machine shop.
75 Tips
Bruce (VA)
Well-known Member
" I don't think I have a copper wire to the distributor."
Look again.
The coil has 2 wires going to the distributor; the secondary wire from the coil to the middle of the cap & the primary wire from the coil to the side of the distributor. Inside the distributor, a copper strip goes from the insulator to the points.
" I have replaced the condenser twice,"
Chances are about 9 out of 10 that you do not have, and did not have, a condenser problem.
" I filed the contacts on the points"
You just took the thin metallic coating off of them. For now, get the tractor running then replace the points. They will burn pretty soon.
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
Look again.
The coil has 2 wires going to the distributor; the secondary wire from the coil to the middle of the cap & the primary wire from the coil to the side of the distributor. Inside the distributor, a copper strip goes from the insulator to the points.
" I have replaced the condenser twice,"
Chances are about 9 out of 10 that you do not have, and did not have, a condenser problem.
" I filed the contacts on the points"
You just took the thin metallic coating off of them. For now, get the tractor running then replace the points. They will burn pretty soon.
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
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