emwolb01

Can't get spark from the opti. I have MSD opti, MSD coil, MSD 6AL2 ignition, Howell wiring harness. My question is, with the MSD ignition do I still need to have wires going to the original factory ICM? Seems that power /trigger to the coil comes from the MSD instead of coming from the ICM. But the harness I have has a connector that fits into the original ICM. A/D have power, and the white wire goes to B5 IGN Control on the ECM. Pin A has 12v but Pin D only has 6v. I'm not sure if those mean anything with the MSD 6AL installed.

I spoke with MSD and they said it should be hooked up but I'm looking for a second opinion. I can get by without Pins A/d but what about the IGN Control wire?

68blvert

I don't know how the MSD box wires in but on the factory system icm needs plugged in as it's controlled by the pcm. key on, back probed at icm, terminal A/ battery voltage, terminal D/ about half battery voltage depending on resistance on primary circuit of coil, terminal C good ground, terminal D, Ignition Coil Module control circuit, is controlled by PCM by making the circuit go high or low, thereby giving the icm the amount of on/off time. You can test pcm control of icm by unplugging the icm module, hook a test light to positive side of battery and other end to terminal D of connector. crank engine, test light should flash on and off. if no flash it's 1 of 3 things, circuitry problem from pcm to icm connector or bad pcm or no reference and/or resolution signals from distributor. In short, yes, you need circuit 423 (terminal D), for the coil to fire. the module needs to be told by the pcm when to work.

Shark Racer

The ECM/ICM is going to command actual timing advance, I'd imagine it has to be hooked up.

lionelhutz

No, I can't see how you could use the stock ICM. It would make sense that the Opti goes to the PCM, the PCM output triggers the MSD box and the MSD box operates the coil.

The factory configuration had power going to the coil on one connector and then 2 wires from the other coil connector go to the ICM. So, I have no idea how you are getting 12V and 6V on the ICM terminals A and D with the coil connected to the MSD box. There should be no voltages on that connector. I guess terminal B could have voltage, but that wire should only go to the MSD box and not be left connected to an open dangling connector.

lionelhutz

I took a look at the MSD manual. The LT1 is a 2 connector coil so following the wiring on page 13 of the MSD box manual combined with the LT1 stock wiring this is what I come up with.

In factory form, terminals A & D on the ICM go to a connector for the stock coil. The second coil connector is switched power which powers the coil and the ICM via an internal connection in the coil.

I'm not sure what you have for connectors or wires now, so I'll just describe the ICM wiring;

A is a pink/black wire. It goes to the red wire on the MSD box. It should also have switched ignition power applied. If you don't have this connected to a switched power source then you need to add it. If your harness has a switched power wire already spliced it into the ICM pink/black wire then you are good to go by connecting the ICM pink/black and the MSD red. If you have already connected a switched ignition source to the MSD red wire then you are good to go by just connecting the ICM pink/black to your currently powered MSD red wire.

B is the white wire and it only goes to the PCM terminal B5, not the MSD box.

C is a black wire and it is grounded.

D is a white/black wire and goes to the white wire on the MSD box.

The coil connects to the MSD box only, meaning no other wiring. The MSD orange wire goes to the pink/black wire that used to go to the ICM. The MSD black wire goes to the white/black wire that used to go to the ICM. You can also tie in the second coil connector by wiring pink to pink/black and/or white to white of the first connector.

So, the short answer is that starting with the stock wiring, you cut the wires at the coil connectors and connect the MSD red and white wires to the harness side and the MSD black and orange wires to the coil side. It's just like the MSD manual shows except the harness wires are striped instead of solid.

emwolb01

Replaced the ICM and it got spark. In the end I used the ICM and the MSD-6AL together. I ended up tracing the wires and it showed that the 6AL supplies Coil power and the ICM works with the PCM. Also read up on this forum about using the thermal grease on the ICM. Good to know. Thanks for the help guys.