Start relay
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Joined: Jun 2018
Posts: 2,362
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From: Everett, WA
A lot of times it's not used,
On older ignition systems that used a distributor it was used to supply power to the coil while the key was in the "CRANK" position, it also probably has an "I" by it, stands for ignition
On older ignition systems that used a distributor it was used to supply power to the coil while the key was in the "CRANK" position, it also probably has an "I" by it, stands for ignition
+1 ^^^
Yes it is/was the "I" terminal
Up until the late 1970's ignition coils were not that good, and wouldn't last very long if they were run at 13.5-14.5volts(engine running/alternator voltage)
So car makers installed a Resistor wire or Ballast resistor on the coil's "+" wire to reduce the voltage by 4 volts to about 10volts, which still provides a hot enough spark
But................when you are starting an engine the starter motor pulls alot of amps, so 12volt battery voltage drops down to 9 or 10volts, with coil resistor that's 5 or 6volts at the coil and NOT a hot spark, lol
And that's what the "I"(ignition) post is for, it would be hooked to Coil + and when starter relay closes the "I" post also has battery volts just like the "out" post to starter motor
So by-passed the resistor to give Coil a higher voltage when starting
These often also had a Diode to prevent Coil "+" voltage, while running, from back feeding into the relay
Yes it is/was the "I" terminal
Up until the late 1970's ignition coils were not that good, and wouldn't last very long if they were run at 13.5-14.5volts(engine running/alternator voltage)
So car makers installed a Resistor wire or Ballast resistor on the coil's "+" wire to reduce the voltage by 4 volts to about 10volts, which still provides a hot enough spark
But................when you are starting an engine the starter motor pulls alot of amps, so 12volt battery voltage drops down to 9 or 10volts, with coil resistor that's 5 or 6volts at the coil and NOT a hot spark, lol
And that's what the "I"(ignition) post is for, it would be hooked to Coil + and when starter relay closes the "I" post also has battery volts just like the "out" post to starter motor
So by-passed the resistor to give Coil a higher voltage when starting
These often also had a Diode to prevent Coil "+" voltage, while running, from back feeding into the relay
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Joined: Oct 2020
Posts: 67
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From: Cody, WY
Thank you. If you look at the very left of pic you can see a wire with terminal end. There are actually two wires and I am wondering if I shoul connect. The starter when it turns engine has sounded a bit funky, even not engaging last winter. I have been concerned about ring gear meshing with starter. Maybe I will connect these to the post to see how effects.
Member
Joined: Jun 2018
Posts: 2,362
Likes: 393
From: Everett, WA
Thank you. If you look at the very left of pic you can see a wire with terminal end. There are actually two wires and I am wondering if I shoul connect. The starter when it turns engine has sounded a bit funky, even not engaging last winter. I have been concerned about ring gear meshing with starter. Maybe I will connect these to the post to see how effects.
From what I can see of that wire, that flat end and that little spring, It's what's left of an old fuse holder, I have no idea what the previous owner added and used that fuse for, you'll need to follow both wires and see where they go
Last edited by 2011Supercab; Aug 9, 2021 at 09:22 PM.
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