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Pertronix Ignitor II with Factory Tach
#1
I installed the Pertronix Ignitor II conversion in my distributor and have been having trouble getting my factory tach to read accurately. I installed it following Wolverine's wiring diagram (http://www.7173mustangs.com/thread-pertr...pped-fords) but the tach was still jumping around. I called Pertronix and they told me to take out the Flamethrower 2 ignition coil I had in there and replace it with a "stock coil or a coil with the same primary resistance as stock".

So today I went down to the auto parts store and picked up 2 coils. The stock one they had:

(http://www.napaonline.com/Catalog/Catalo...0359708477)

Which has a 1.5 ohms primary resistance and 24,000 max voltage.

I also picked up a Flamethrower I that has a 1.5 ohms primary resistance and 40,000 max voltage.

I then tested them both out and each gave me the same results. The tach read smoothly with no jumping. However when I hooked up the timing gun to read actual RPM the tach was off. This is what it read:

Tach: 1,000 / Actual: 2,500
Tach: 2,000 / Actual: 3,300
Tach: 4,000 / Actual: 4,000

Does anyone have any suggestions on what I might do from here or where I went wrong?

'72 Mach 1
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#2
Might you have a spare P2? Or, perhaps someone near you may have a spare you can swap out.

I have scoped a pair of P2's. The signal to the coil is interesting to say the least.

[Image: 11jmcuc.png]
351C Bold Manners, Brash Attitude
Favorite Teams: Michigan Wolverines and Whoever Is Playing Ohio State.

When I drive past a herd of cows, the cows MOO at me
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#3
I don't have a spare on hand. Do you really think that might be the issue? I was wondering if the problem might be with the tach it's self.

'72 Mach 1
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#4
I started with the Pertronix Ignitor III and Flamethrower coil, with a direct 12V connection, never could get he stock tac to function correctly plus had some starting issues. Did some rewiring tac functioned but was way off, finally went to the Petronix l and stock coil, using the original resistor wire....problems resolve with the tac, even started better, much better. You loose some of the functions the Ignitor lll offers over the l but do you really need them?

Jim

M code 71 Mach 1, 351 4V Cleveland, Ram Air (not factory), C6 Trans, 3.5 rear
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#5
Jim and Jutta;107243 Wrote:I started with the Pertronix Ignitor III and Flamethrower coil, with a direct 12V connection, never could get he stock tac to function correctly plus had some starting issues. Did some rewiring tac functioned but was way off, finally went to the Petronix l and stock coil, using the original resistor wire....problems resolve with the tac, even started better, much better. You loose some of the functions the Ignitor lll offers over the l but do you really need them?


I might as well go pick up an Ignitor I and see if that helps. Do you still need the 12v bypass wire with the I1 like the I2?

'72 Mach 1
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#6
scoot302;107242 Wrote:I don't have a spare on hand. Do you really think that might be the issue? I was wondering if the problem might be with the tach it's self.

1. Can you confirm you are getting 6V to the coil and 12V to the Pertronix?

2. You can always put in original points and see what happens.

3. With points I never had a tach issue regardless of the coil. You just have to be sure you are getting 6 volts at the points and the coil.

[Image: 11jmcuc.png]
351C Bold Manners, Brash Attitude
Favorite Teams: Michigan Wolverines and Whoever Is Playing Ohio State.

When I drive past a herd of cows, the cows MOO at me
  Reply
#7
Wolverine;107257 Wrote:
scoot302;107242 Wrote:I don't have a spare on hand. Do you really think that might be the issue? I was wondering if the problem might be with the tach it's self.

1. Can you confirm you are getting 6V to the coil and 12V to the Pertronix?

2. You can always put in original points and see what happens.

3. With points I never had a tach issue regardless of the coil. You just have to be sure you are getting 6 volts at the points and the coil.

I believe I was getting the right voltage when I tested it during the initial install. I have a new set of points so I will check the voltage again and test with points on Monday.

'72 Mach 1
  Reply
#8
scoot302;107255 Wrote:
Jim and Jutta;107243 Wrote:I started with the Pertronix Ignitor III and Flamethrower coil, with a direct 12V connection, never could get he stock tac to function correctly plus had some starting issues. Did some rewiring tac functioned but was way off, finally went to the Petronix l and stock coil, using the original resistor wire....problems resolve with the tac, even started better, much better. You loose some of the functions the Ignitor lll offers over the l but do you really need them?


I might as well go pick up an Ignitor I and see if that helps. Do you still need the 12v bypass wire with the I1 like the I2?

You don't need the 12V bypass wire with the Petronix 1, you should use the resistor wire from the Tac, the Petronix 1 doesn't need the full 12Volts.

Jim

Jim

M code 71 Mach 1, 351 4V Cleveland, Ram Air (not factory), C6 Trans, 3.5 rear
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#9
They aren't the most accurate tachs anyway.... Might consider a rocketman conversion to modern movement.

1973 Mach 1 Q code 351 4V, 9A paint, standard interior, 3.50 rear, C6 trans.
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