Ignition control module (ICM)

[z_ya]

The car is a 1978 280Z during lunch break today I pulled it and tested it on the machine. The tester had failed it at low rpm but passed it at high rpm. The car did die twice today when i came to a complete start and was a pain to start. I do have one on order that should arrive Wednesday. Is it normal for it to pass a high rpm an fail on low?

[TomoHawk]

I had a similar problem once. The engine would stall at a stop sign. The distributor pickup gap was too big.

[Willoughby Z]

The ICM is a "black box" device. I was having very random issues- rough running, stalling (no start), tach going haywire...

Had an electronic tech friend compare a new with the old. No discernable difference. Replaced the old, suspect ICM with new. No problems since.

[TomoHawk]

There is a recent thread about installing a GM HEI ignition module into the '78. People have reported success with it, and the OE ignition box is no longer needed. It's cheap enough you can buy lotsa spares for what the OE ignition box costs.

Edited May 12, 2013 by TomoHawk

[ZCurves]

I tried the HEI conversion without any luck. I know that others have been successful with, I just could never get it working correctly.

I wound up replacing the Ing Module and the Key Lock switch and that licked the problem. You can find a Ign Module here:Standard LX513 Ignition Control Module Datsun Nissan New | eBay

No need to pay more than $100 for a new one since there are plenty of them out there.

[TomoHawk]

When you install the GM ignition module, what do you do with the wires already connected to the coil? I know you should disconnect the OE ignition box.

[FastWoman]

Andrew, did you have the tach/ECU wire connected? If not, the ECU wouldn't have been triggered, and it wouldn't have delivered any fuel.

Tomo, if I recall correctly, you keep the + wire intact. Then on the - side of the coil, there will be two wires. One will go to the old ignition module. (You can disconnect that one.) The other will go to the tach and ECU (see above). You need to preserve that one. And then there's the connection you add from the HEI unit to the - of the coil.

I took my ignition module completely out, but I kept the plug and wiring intact, so that it could be easily re-installed or replaced with OEM. As I recall, I simply folded back the ground wire to the coil and taped it up.

[TomoHawk]

Thanks Sarah. I forgot about the ECU wire. It's a black wire that connects to pin 1 on the ECU, but I can't tell which black wire.

Edited May 14, 2013 by TomoHawk

[ZCurves]

I may try this again, I believe the HEI solution is the best and people should try it. Sarah, maybe (please ) you could do a write up with pictures of what you did to your Z. There are a lot of instructions on the web, but none of them are thorough and few have pics from a later model S30.

[TomoHawk]

Most of the write-ups I have seen are for the 240Z distributor swap or something else, like a general description, but none specific to the L28E engine.

[FastWoman]

Tomo, just trace the wires with a multimeter! You might need an assistant, but hold one probe on the ECU #1, and the other on one of the disconnected mystery wires. If you've got continuity, that's the one.

Andrew, I hate to say I'm in "life gets in the way" mode right now. We start building a dock on Thursday, and that's only the beginning of all our fun, including landscaping, grading, armoring of our shoreline, waging WWIII on an invasive species of marsh grass, adding on to our home, alternative energy, and probably a few things in the "etc." category. So I can't promise you a good, illustrated writeup anytime remotely soon. Until then, this will have to do (all from memory, so I might have an inaccuracy somewhere):

1. Remove the passenger kick panel, and uninstall the ignition module. Leave the wiring in place, in case you want to revert to OEM configuration in the future.

2. Locate the terminal block (a tiny black clamshell on the inside driver's fender) where the distributor's pickup coil connects to the wiring tree. Take apart the connections, and remove the terminal block, making sure to save it for later reversion to OEM. You may use the same threaded mounting holes to mount your HEI module.

3. Disconnect the wires from the (-) post of your ignition coil. Identify the wire that has conductivity with the #1 connector on to your ECU (beneath the driver's side kick panel), and reinstall it on the coil. Fold the remaining wire back on itself, and wrap it up in electrical tape. You may pull this wire back out later if you wish to revert to OEM.

4. Mount your HEI module to a good heat sink, and mount that heat sink to the fender, using the old terminal block's threaded mounting holes. Use heat sink compound between all mating faces. It is very important to have a good ground between the module and the body.

5. Replace the pickup coil's ring connectors with female spade connectors. Connect red to "W" and green to "G" on the HEI module. Lube all connectors with silicone dielectric grease, both here and below!

6. Install a wire from the HEI's "C" to the (-) terminal of the ignition coil.

7. Install another wire from the HEI's "B" to the (+) terminal of the ignition coil.

Additional notes:

See Tomo's diagram in post 19 of this thread for pin positions:

http://www.classiczcars.com/forums/engine-drivetrain-s30/45070-gm-hei-upgrade-78-280z.html

One person on this forum once swore that you should run a very beefy wire directly from your IGN+ circuit to the HEI's B terminal. However, the heavy current handling of the HEI is only from the coil to ground. The B terminal merely feeds the module's internal circuitry, so I don't think it has to be particularly beefy. You'll run the same +12 to the coil via the supply wire that was there to begin with, and it is heavy enough to support the current demands of the coil. The HEI module can simply be supplied with a small'ish branch off of that, perhaps 16 gauge.

I used a square, finned heat sink for a power transistor to mount my module. I did this out of conservatism. Others (Steve Blake) have said no heat sink is necessary and that mounting directly to the fender is adequate. This makes sense, as the module is ordinarily in a pretty hostile (hot) environment, crammed inside a distributor.

There are different versions of the HEI module. They all wire the same way, but some are higher specification (e.g. for very high RPMs). I used a very cheap/ordinary one, and it's worked great.

My own successful installation was based on this writeup for a 240:

GM HEI retrofit

Edited May 15, 2013 by FastWoman

[TomoHawk]

Here is the diagram you mentioned:

[ATTACH=CONFIG]63429[/ATTACH]

Edited May 15, 2013 by TomoHawk