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Discussion Starter · #1 ·
Hi Everyone,
I have a 1974 cl360 that I just finished a full engine rebuild on. I have the engine back in the frame but when I went to try to fire her up, I'm not getting spark at either plug. I also have a Pamco unit that I know was working fine when I pulled the engine from the frame about two months ago. Here's what I've checked so far:

-Verified battery is fully charged on the battery tender and is showing 12.8v
-Verified main ground and Pamco ground are clean and making good contact with paint free areas of the frame
-Traced ~12v from battery -> solenoid -> ignition switch -> coils -> plug caps

The confusing thing to me is that with the ignition switch on and the start button not pressed, I'm seeing 12v at the spark plug caps. If I press the start button, this drops to 10v at the spark plug caps.

I don't think the caps are the issue since they're brand new ngk caps on brand new plugs, and they're both showing good resistance when I checked them.

I guess my question is, at what point in this chain should I see voltage drop to 0 when the start button is not pressed:

Battery + -> solenoid -> ignition switch -> black/white wire to coils -> coils -> blue / yellow wire to green/white wire of pamco -> pamco -> coils -> plug cap -> plug

I thought the pamco should drop voltage to 0 then as the sensor turns it will fire the coils to much higher than 12v, but I could be wrong about how this works.

Thanks for your help everyone, I really appreciate any advice you have to offer.
 

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Even with points, the coils fired on loss of voltage. 12v provides a magnetic field in the coil. When voltage is removed (points opening, Pamco stopping voltage to coil) the collapsing magnetic field caused a high voltage to be generated.

Typical pamco issues are broken solder joints or legs on sensors. The pamco, like points, has 2 separate circuits for each cylinder. The processor is common to both. So seeing 12v at plug cap is normal, but if processor or sensors not wired correctly, or electrically damaged, then 12v is not removed at firing time. Without clearer description, it is hard to diagnose over the web.

Carefully check wire continuity and grounds. Check for broken solder joints, sensor legs....it could be a bad Pamco, but they are pretty durable otherwise. Mine is still fine after over 4 years.

Sent from my SM-T830 using Tapatalk
 
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