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Voltage at the coil

I

IMP

Member
Can anyone tell me for sure what the voltage is suppose to be at the coil + measuring to engine block? In a short amount of time I went through two condensers. So I checked the voltage at the coil and found it at 5.5v. Internet searches told me it should be 8-9v. Can anyone confirm that? Tonight I changed out my ballast resistor from 2.5 ohm to 1.3 and now my voltage at the coil is about 7v. I plan on going back to Napa an get a 1ohm resistor and see if that gets me closer to 8-9. These measurments were taken with the engine off. So add 2v when engine is running. My coil is a IC903 and I measured about a 1.6 ohm on the primary. This is on a Dodge 251 Flathead engine. J5 Bombardier
 
here is the napa numbers I run with no trouble resistor#icr13----coil #ic12sb-----if you have voltage trouble it should be burning up points----I bought my sv200 not running ---lol there was a pile of dist. parts in the cab on the floor--everywhere----it even had a after market electronic pointless junk /burned up conversion kit in it----20 min. at home reusing parts laying in cab I drove it off the trailer------so when I gave it a tune up the above part numbers is what I used-----take note-----the only trouble I have is when its super cold out I use a jumper across the resistor and it starts like its summer---I give it like 30 sec. and I unclip the jumper----I plan on putting in a switch across the res.for cold start ups-----I groom every day and my dist. set up and dry gas keep me from walking home-----btw napa has a coil with a built in res. but ive never tried one
 
forgot ---it even had a new carb. on it---?----but no spark-----how was a carb going to fix no spark-----lol----grooming the runway for the grandson ---he loves his updated 120 with electric start
 

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ICR13 is the resistor I used to get me to 7 volts at the coil. I asked the Napa guy if he could tell me what the difference is between the ic912 and ic903 coils and he said the specs. look the same. When I wired my J5 ignition I used the momentary ignition key on switch to bypass the ballast resistor during start up. It works fine I just need to know what the voltage is suppose to be to get it dialed in.
 
If you want a full 12v at the coil for cranking all that is needed is a wire from the small post on the solenoid to the coil. When you quit cranking then the current goes through the resistor.
Mike
 
+ plus one for the stone breaker.

Unless, it is a 6V flat head with a 12 v conversion (alternator on it)

I don't know my part numbers, but different coils need different voltages.

Look at the condenser as a sponge. they really don't do anything but absorb and dispense stabs of electrons. If you are eating them your points are out of time with the rotor. Dwell is important. a little play in the rotor and cap will make you pull your hair out.

Verify the condenser is grounded well.
 
Yea stonebreaker I like that method! I heard from a different source that 8-9v is what I need at the coil. So with my engine running that's what I should have with the ICR13 ballast resistor. Ill measure it tonight with the engine running and see how my condenser holds up.
 
i used a pertronix for my 250 I6 in my sv200. when i ordered the kit i ordered a matching coil. starts good in the cold. i agree that basic points are easy to work on and easy to keep a spare part or two but you can tell the difference with the new ignition with the hotter spark in the way the motor runs.
 
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