Finally getting around to cranking my install. I've got great oil pressure and I've got fuel pressure in the rail. However I've got no spark at the coils.

I have tach readings, so that says to me that I likely have a good CPS. The ICM ground wire is grounded where the battery negative is. I read something when searching on here that the ICM body also needs to be grounded? I've relocated my coilpacks & ICM to where my battery used to be located. Do I need to place grounds on the mounting bolts and bolt them to the block?

Thanks,
Chris

I think the back plate of the ICM does need ground, and you'll probably also want to make sure it's mounted on something that works as a heatsink. I think it gets rid of heat via the back plate.

I haven't done my ignition setup yet (for my 3800 swap) but looking at the module, I think that back plate is the chassis ground for the module. Also, make sure the coil packs are super snug on there..

No, there is a ground wire that goes from the coils to the motor typically that needs to be grounded..

I would just check all of the ground routing, then go from there.

Thanks for the quick replies. I will double check my grounds. Since the tach signal comes from the ICM and the ICM gets it's signal from the CPS can I safely assume the ICM is getting power and correct signal from the CPS?

When you say ICM body do you mean the coil pack?yes as far as I know the backing plate to the coil packs should be grounded.

quote Originally posted by James Bond 007: When you say ICM body do you mean the coil pack?yes as far as I know the backing plate to the coil packs should be grounded.

Yes, the ICM behind the coil packs where the mounting bolts are. Thanks, I will try grounding that as that may be the issue.

I hate to disagree with so many people who have said it...
but I have started and run my 3800 just fine with the coil pack not mounted to anything.....

On my 3800 that I purchased, there was a ground that was broken off that goes to a stud that holds the coil pack mount onto the engine. This may be a good place to check to make sure that ground's not broken and it's connected

------------------

I wish there was a single opinion on whether or not it needs to be grounded. I guess it can't hurt to ground it so I will do that first. Can anyone comment on my question from above:

quote Since the tach signal comes from the ICM and the ICM gets it's signal from the CPS can I safely assume the ICM is getting power and correct signal from the CPS?

Again, thanks for the replies and experiences shared.

[This message has been edited by iSh (edited 08-04-2009).]

Bump for more ideas I want to try to get it to crank this weekend, car is not at my location during the week so I can't test until the weekend.

The base does NOT need to be grounded, and you can confirm that yourself by looking at how nothing connects to the base area other than plastic. If anything it needs to be isolated from ground.

I very typically see people that rewire these ICM harnesses screw them up in some form, either from bad wiring splices and miswired, or because they did not plug things in very well.

The block and chassis itself also needs to have the correct grounds.

quote Originally posted by darkhorizon: The base does NOT need to be grounded, and you can confirm that yourself by looking at how nothing connects to the base area other than plastic. If anything it needs to be isolated from ground. I very typically see people that rewire these ICM harnesses screw them up in some form, either from bad wiring splices and miswired, or because they did not plug things in very well. The block and chassis itself also needs to have the correct grounds.

I believe all the wiring on the ICM is intact as it came from the car the motor was pulled from other than the power and ground wires. Of course I'd have to look at my notes again (used Sinister Performance notes) to be certain I did not touch anything else.

What are the absolutes for the ICM to give me spark? I'd like to narrow my search. Like I said, I have accurate tach signal so I think I can rule out CPS and Power.

Thats it, it needs no other inputs, just power and ground. The block needs to be grounded as well.

I would consider possible icm / coil issues at the moment.

quote Originally posted by darkhorizon: Thats it, it needs no other inputs, just power and ground. The block needs to be grounded as well. I would consider possible icm / coil issues at the moment.

Thanks for the quick response. If I had grounding issues with the ICM would the tach signal still be accurate? I will double check all grounds for possible issues.

The whole thing has been sitting up for 3 years so maybe something went bad... How do you test the ICM and Coils? I am sure there is a proper procedure somewhere. My manual covers 15 years and 4-5 different motors and sucks otherwise I would go by what it has to say.

You can take the ICM to your local parts store and have it tested. Just hope it's not bad, because a new replacement is hella expensive.

quote Originally posted by darkhorizon: Thats it, it needs no other inputs, just power and ground. The block needs to be grounded as well. I would consider possible icm / coil issues at the moment.

It needs no signal from the ECU to know to spark? How does it know the O2 readings and if to retard or advance timing? There's got to be something more with this?

quote Originally posted by iSh: It needs no signal from the ECU to know to spark? How does it know the O2 readings and if to retard or advance timing? There's got to be something more with this?

Nope, there is no influence from the ecu, it will spark fine on base timing without any ecu input. The ECU can advance spark, but it cant turn it off completely

hrm... How do you test coils? I find it hard all 3 could have gone bad..

Haven't had a chance to get my ICM to the parts store for testing yet, but figured I would give this a bump to see if anyone else can comment on the situation. Again, I am getting tach signal from the ICM so I think some portion of it must be working.

Sometimes the pink wire on the IMC harness gets a short in it and causes A no spark condition, Mine did that till I finally found the source, try wiggling the pink wire on the imc harness and see if it starts then.

The only ground for the coils is the one built into the harness that attaches to the engine. Double check to make sure you have the wiring correct especially the connector that connects to the small harness coming from the ign mod harness. Pin A goes to the PCM and pin E goes to the tach both are white and if they get mixed up the engine will not run. Dan