So I've got a few CNP's sitting here on my desk from a friend. They're the truck style with the little aluminum fin heat sink. What exactly are the pins? I assume power, ground but there are 2 others, 1 is the signal but a 4th? I have some background as too how they fire but I'd like to check them all out with a simple 555 circuit .

 

I don't know which pin is which, however, the pins will be: +12V igniton switched, power ground (to block), trigger signal (from ECM), and trigger ground (from ECM).

RBob.

 

How can I tell which pin is which? This might break all my hopes of getting CNP on the car before summer .

 

Have any wiring harness pieces for it? GM typically has some common colors: pink w/blk stripe for +12 V, black w/white stripe for grounds, green, blue, orange, or purple for signals. The ECM trigger ground will be common to one wire to go back to the ECM. The power grounds are typically individual and tied close by to the engine.

RBob.

 

Yeah, I don't have a wiring harness, just the coils.
2 of the 4 pins are labeled "I", nothing, nothing, "3" .

 

I happen to have a set of truck coils with the factory wiring still attached.

If you orient the coil so that you are looking into the 4-wire receptacle, with the coil oriented so that the heat sink fins are beneath the connector, pin A will be on the left, and pin D will be on the right.

Pin A = chassis(?) ground (black)
Pin B = ref(?) ground (brown)
Pin C = trigger (color varies by cylinder)
Pin D = 12V power (pink)

What I can't tell for sure from the coil harness is which is the chassis ground, and which is the trigger ground. From the wire color, I would expect that the black wire (pin A) is the chassis ground, but I can't be 100% certain.

 

Dave, I believe you are correct and thanks.