My 6 volt, positive ground 9n/2n with front mount distributor won't start - no spark. Continuity tests on distributor check out OK. I notice that with key turned on the resistor gets too hot to touch. I put in a new wiring harness, did I connect something wrong? Any other suggesstions?
- Thread starter RPond
- Start date
Are you talking about the wire wound resistor on the back of the
dash? If so, I would think that is normal if your points are closed.
Don't leave the key on long or your coil will not be good.
I would take the distributor off and clean/gap the points.
They may have slipped or worn off so they are not opening.
Replace them with quality points if needed, not TSC etc.
I like Standard Ignition BlueStreak part # FD-6769X.
NAPA/Echlin premium are also highly rated. Part #CS35
dash? If so, I would think that is normal if your points are closed.
Don't leave the key on long or your coil will not be good.
I would take the distributor off and clean/gap the points.
They may have slipped or worn off so they are not opening.
Replace them with quality points if needed, not TSC etc.
I like Standard Ignition BlueStreak part # FD-6769X.
NAPA/Echlin premium are also highly rated. Part #CS35
If your points open there should be no current flow and that
resistor should cool off. It may take a while though.
No "good" test to tell if a coil is good on the bench, but there
are other things you can check.
Put a meter or test light on the top of the coil and roll the engine over.
Key on of course. It can be rolled by hand.
Voltage should be battery voltage with points open, roughly half
that when closed. A test light should blink/dim indicating the same.
If it does not have battery voltage with the points open, something
is grounded inside the distributor. Most likely the little pig tail where
the condenser connects, the insulator where it connects is bad
or the little copper strip is touching something it shouldn't.
There are other possibilities, like a bad condenser, but they are
less likely than just the wire or the little copper strip touching.
resistor should cool off. It may take a while though.
No "good" test to tell if a coil is good on the bench, but there
are other things you can check.
Put a meter or test light on the top of the coil and roll the engine over.
Key on of course. It can be rolled by hand.
Voltage should be battery voltage with points open, roughly half
that when closed. A test light should blink/dim indicating the same.
If it does not have battery voltage with the points open, something
is grounded inside the distributor. Most likely the little pig tail where
the condenser connects, the insulator where it connects is bad
or the little copper strip is touching something it shouldn't.
There are other possibilities, like a bad condenser, but they are
less likely than just the wire or the little copper strip touching.
Finally got back into the shop today. Did the test light attached
to the coil. Got blinking light as I rolled the crank. Still no start,
so I tried the test with a meter instead of a light. With key on
getting battery voltage with points open but no voltage at all
with points closed. What do you think May be wrong?
to the coil. Got blinking light as I rolled the crank. Still no start,
so I tried the test with a meter instead of a light. With key on
getting battery voltage with points open but no voltage at all
with points closed. What do you think May be wrong?
Bruce (VA)
Well-known Member
You've got a dead short in the distributor.
Go back & do those continuity checks again.
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 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).
10. Burned rotor, cracked/carbon tracked cap.
After 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.
Pls post back w/ results or more questions.
* 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
75 Tips
Go back & do those continuity checks again.
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 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).
10. Burned rotor, cracked/carbon tracked cap.
After 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.
Pls post back w/ results or more questions.
* 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
75 Tips
Thanks, Bruce. I took the distributor back off and did the four continuity checks and passed them all. Put it back on the tractor and did the voltage test again. Same thing - battery's voltage alternating with no voltage as the crank rotates. Any other ideas. I put on a wiring harness, could I have something connected wrong?
Bruce (VA)
Well-known Member
I think you have a meter or measuring problem.
Measure voltage across the battery terminals.
You should see battery voltage (6.25 to 6.35 volts or so)
Now, turn the key on & put one probe on the top of the coil & the other firmly grounded to the chassis.
You should see battery voltage or something less than half of battery voltage (not 0)What do you see?
Next, bump the starter & do the same test; again, you should see the opposite of what you just saw. (if not, bump the starter until you do)
Post back w/ results.
75 Tips
Measure voltage across the battery terminals.
You should see battery voltage (6.25 to 6.35 volts or so)
Now, turn the key on & put one probe on the top of the coil & the other firmly grounded to the chassis.
You should see battery voltage or something less than half of battery voltage (not 0)What do you see?
Next, bump the starter & do the same test; again, you should see the opposite of what you just saw. (if not, bump the starter until you do)
Post back w/ results.
75 Tips
Bruce, here's how my Sunday afternoon project went. The voltage reading at battery posts was 6.3. Voltage at the coil post to ground is also 6.3 with key on. Rolling the engine over the voltage drops to less than 1 volt. I keep wondering if something is connected backward. Thanks
RPond
RPond
Bruce (VA)
Well-known Member
" I keep wondering if something is connected backward. "
Outside of the distributor? No.
That's why I suggested checking voltage again at the top of the coil.
You either have battery voltage there or you don't.
You do.
Therefore.....and I know you don't want to hear this......the problem is inside the distributor.
Try it again. Wiggle the coil to see if the pig tail is grounding. Double check the insulator & coil strip.
Your points are grounding.
75 Tips
Outside of the distributor? No.
That's why I suggested checking voltage again at the top of the coil.
You either have battery voltage there or you don't.
You do.
Therefore.....and I know you don't want to hear this......the problem is inside the distributor.
Try it again. Wiggle the coil to see if the pig tail is grounding. Double check the insulator & coil strip.
Your points are grounding.
75 Tips
Bruce (VA)
Well-known Member
Bruce, I will recheck the distributor internals but first I jumped the ballast resistor as you suggested. Except for being old and probably original mine looks like your picture and it's the only one. With the top posts jumped, voltage at the coil again is 6.3, but now goes to 3 volts as the engine is rolled over. If I understand correctly that is the way it should be. But, if this makes any difference - the alligator clips on the jumper wire where too hot to touch within a few seconds. Does that indicate a problem? Thanks for your help. RPond
Bruce (VA)
Well-known Member
" Does that indicate a problem?"
Short answer.....probably not.
Long answer....that would depend on the gauge of the jumper wire & how tight the connections were.
Check the resistance of the resistor. Key off, it should read .3 ohms. Maybe not even enough to show on your meter.
Next, jump the resistor & check for spark.
75 Tips
Short answer.....probably not.
Long answer....that would depend on the gauge of the jumper wire & how tight the connections were.
Check the resistance of the resistor. Key off, it should read .3 ohms. Maybe not even enough to show on your meter.
Next, jump the resistor & check for spark.
75 Tips
The ohms reading of the resistor is about .3 as you said it should be. The bad news is the coil voltage reads less than1volt again alternating with 6.3 even with the resistor jumped
If there.is an internal short in the distributor how come it passes all four continuity tests. I'm still not getting any spark
If there.is an internal short in the distributor how come it passes all four continuity tests. I'm still not getting any spark
Bruce (VA)
Well-known Member
" If there.is an internal short in the distributor how come it passes all four continuity tests."
Because it can't be anywhere else.
You either have a bad meter or you're missing something on the continuity tests.
I don't think you have a bad meter because everything else checks out as it should.
" I'm still not getting any spark "
How are you checking that? W/ the distributor back on the tractor & the starter turning the engine over & using a test plug or plug checker?
Think about it this way......
When the points close in your distributor, the primary circuit becomes OPEN. It's supposed to be CLOSED.
So, trace the circuit.
The primary circuit goes from the pigtail to the insulator on plate (where the brass screw attaches)
From there, it goes to the copper strip, then to the points.
Check for continuity all the way to the points.
Because it can't be anywhere else.
You either have a bad meter or you're missing something on the continuity tests.
I don't think you have a bad meter because everything else checks out as it should.
" I'm still not getting any spark "
How are you checking that? W/ the distributor back on the tractor & the starter turning the engine over & using a test plug or plug checker?
Think about it this way......
When the points close in your distributor, the primary circuit becomes OPEN. It's supposed to be CLOSED.
So, trace the circuit.
The primary circuit goes from the pigtail to the insulator on plate (where the brass screw attaches)
From there, it goes to the copper strip, then to the points.
Check for continuity all the way to the points.
try this. bypass all the tractor ignition wireing, and run a hot wire from the battery to the top of the coil. put a test lamp inline with it. roll over.. lamp should blink. if so try it without the test lamp and see if you get spark. short duration test won't hurt the coil.
this tests tells us if there are any shorts in the dizzy from col to points, and if points open.
we can go from there.
this tests tells us if there are any shorts in the dizzy from col to points, and if points open.
we can go from there.
Sweet success!! Got Dad's old 9n started today! The problem was a bad coil. I didn't suspect because it was relatively new. Swapped for the crappy old coil and guess what - spark! After a few tries got her purring like a kitten! After church today I asked my 80 year old friend for his advice - he used to be a mechanic in younger days. His advice: keep swapping parts until you find the bad one. His number 1 culprit: the coil. I sure didn't realize till now that the coil would pass the continuity tests and still be defective. I'm sure I will have more questions, but I'll start a new post.
Thanks for everybody's help.
Thanks for everybody's help.
Doctor Rick
Member
Never mind, glad you got it and thanks for posting.
Rick
Rick
Bruce (VA)
Well-known Member
" I sure didn't realize till now that the coil would pass the continuity tests and still be defective."
You weren't testing the coil; you were testing for continuity in the distributor.
Do us all a favor........
"test" the coil.
Put you ohm meter probe on the top post & the other one on the pigtail; tell us what you see.
Then, put one probe on the top post & the other on the tab. What did you get?
I never thought to tell you to check the coil simply because they rarely if ever fail cold. Well, this example is rare!
And it makes perfect sense now; the coil was acting like a huge resistor: when the points closed, you got 0 voltage.
Amazing. I learned something.
75 Tips
You weren't testing the coil; you were testing for continuity in the distributor.
Do us all a favor........
"test" the coil.
Put you ohm meter probe on the top post & the other one on the pigtail; tell us what you see.
Then, put one probe on the top post & the other on the tab. What did you get?
I never thought to tell you to check the coil simply because they rarely if ever fail cold. Well, this example is rare!
And it makes perfect sense now; the coil was acting like a huge resistor: when the points closed, you got 0 voltage.
Amazing. I learned something.
75 Tips
Bruce; sorry for the delay in reply, but I get to the shop only on weekends. If I did your test correctly on the bad coil the ohm reading at the pigtail went all the way to the right end of the meter - to almost zero. At the tab, the meter barely budged = stayed at the left end of meter near infinity. To me that doesn't mean much but perhaps to you?
RPond
RPond
Bruce (VA)
Well-known Member
" To me that doesn't mean much but perhaps to you?"
Yep.
It means that the coil is toast; a dead short.
From the top to the pigtail, you should get 3 ohms or so on a 12v coil & 1.5 or less on a 6v coil.
Last question.....
Is the coil cracked any where? Any insulation leaking? Bulging anywhere?
Tnx for the follow-up.
Yep.
It means that the coil is toast; a dead short.
From the top to the pigtail, you should get 3 ohms or so on a 12v coil & 1.5 or less on a 6v coil.
Last question.....
Is the coil cracked any where? Any insulation leaking? Bulging anywhere?
Tnx for the follow-up.
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