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Old 03-03-2018, 04:32 PM   #1
COE Dan
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Default Troubleshooting: need nominal 12v ignition coil/condenser values

Ford Barners,

My 47 COE has been converted a while ago to 12V. I have a 12V stock type coil and condenser (from Macs or similar) running with a Napa ignition resistor for 12V vehicle.

What are nominal values for the coil (primary and secondary resistance)?
What should the matching ignition resistor value be?
What capacitance value (microfarads) should the condenser have?

My truck started having problems about 8 months ago which manifested itself as a slow power falloff and reduction in rpm to zero. No throttle adjustment would recover rpm stability. Once the engine quit, I could turn off the ignition, turn it back on and hit the starter and the engine would catch and I could continue to drive normally.

I've gone through the fuel system and now I'm checking the ignition circuit. Any assistance would be appreciated. Thanks,

Dan
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Old 03-03-2018, 04:46 PM   #2
BUBBAS IGNITION
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Default Re: Troubleshooting: need nominal 12v ignition coil/condenser values

Quote:
Originally Posted by COE Dan View Post
Ford Barners,
mmmmmmmmmmmmmmmmmm

My 47 COE has been converted a while ago to 12V. I have a 12V stock type coil and condenser (from Macs or similar) running with a Napa ignition resistor for 12V vehicle.

What are nominal values for the coil (primary and secondary resistance)?

primary 1.5 ohms, secondary 8500 ohms .....secondary may vary but needs to be in the thousands.........primary must be 1.5 to 3.0 (3.0 if no resistor is used)

What should the matching ignition resistor value be?

1.5 when used with 1.5 ohm coil

What capacitance value (microfarads) should the condenser have?

.25 to .27 pretty standard

My truck started having problems about 8 months ago which manifested itself as a slow power falloff and reduction in rpm to zero. No throttle adjustment would recover rpm stability. Once the engine quit, I could turn off the ignition, turn it back on and hit the starter and the engine would catch and I could continue to drive normally.

Heat? Condensor?? Is the coil hot when dieing ???? Whats the resistance on the coil ???? Too low =too much heat...

I've gone through the fuel system and now I'm checking the ignition circuit. Any assistance would be appreciated. Thanks,

Dan
Try these ....
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Old 03-03-2018, 04:48 PM   #3
COE Dan
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Default Re: Troubleshooting: need nominal 12v ignition coil/condenser values

Thanks for the quick reply. I checked the coil and I'm showing 1.4 ohms on the primary and about 7800 on the secondary (at about 60 degrees - might go up a bit when it warms up). I'll check the resistor and the condenser next. Thanks much!

Dan
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Old 03-03-2018, 04:54 PM   #4
COE Dan
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Default Re: Troubleshooting: need nominal 12v ignition coil/condenser values

Saw your other comments just now. The behavior observered happens occasionally regardless of engine temp. I've had it happen after 20 mins of driving and as little as 5 mins after startup. The coil is mounted in the stock position next to the generator and is elevated above the head by a couple of inches - I don't believe it's getting excessively hot but normal temps might be causing a bad coil to short or open circuit occasionally. The condenser is also mounted in the stock location for a 42 crab cap distributor (truck has the '42 distributor instead of a '47). Ignition resistor is mounted on firewall away from both. Off to check the condenser and resistor...

Dan
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Old 03-03-2018, 05:44 PM   #5
supereal
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Default Re: Troubleshooting: need nominal 12v ignition coil/condenser values

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We are seeing lots of faulty new condensers right out of the box, so we usually reuse the old one if it has been working. A bad condenser will mimic a fuel problem. I carry a spare condenser in my "road kit". It was clip leads on it so it can be attached between ground and the input post of the distributor. If a condenser goes short, that won't help, but an open or weak condenser will produce the problem you outllned because it limits the charging of the coil.
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