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TakemuraShuu

1978 280z, GM Hei Module Problem

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Hi everyone. I was told my ignition unit is starting to go bad due to the complete drop in rpms when mashing on the accelerator when the engine's warm. I was told to do the Hei module conversion.
I installed it according to the diagram below but I'm not getting any spark. I've tried 3 different brand new module and no dice. I have the module bolted down to the chassis inside the engine bar, near the ignition coil. I've looked at the 3 threads on this forum regarding this problem and another on zcar.com, nothing provided any success. Any help would be much appreciated, thank you.

post-2169-14150817827734_thumb.jpg

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They're just the holes used to mount the module.  Not sure, but one of them has a wider grommet.  Just pick a good spot and ground both.

 

But, word is, that if they're not grounded from the start that the module might be damaged.  hopefully you won't find that to be the case. One or both definitely need to be grounded though because that's where the coil current flows, through that ground.  No ground, no coil current (as opposed to voltage).  No current, no spark.

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Have you checked the B pin for voltage?  Checked the red and green wire's resistance, through the distributor's pickup coil?  Checked the resistance of the coil's primary circuit?  Checked for pinched wires?

 

Did you disconnect the old module?  Just unplug it, up by the fuse box.  It needs to be disconnected for the new one to work right.

 

You have wires connected but haven't confirmed that things are correct.  A picture isn't really going to help.  Good luck.

 

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23 hours ago, TakemuraShuu said:

Hi everyone. I was told my ignition unit is starting to go bad due to the complete drop in rpms when mashing on the accelerator when the engine's warm. I was told to do the Hei module conversion.

 

This isn't really a sign of a bad module.  "complete drop in rpms when mashing on the accelerator when the engine's warm"  Module problems are associated with high RPM, but "mashing" isn't necessary.  It's the high RPM that overload it and cause it to fail.

 

If you just can't get the new HEI module to work, consider disconnecting it and reconnecting the old one.

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Quote

Have you checked the B pin for voltage?  Checked the red and green wire's resistance, through the distributor's pickup coil?  Checked the resistance of the coil's primary circuit?  Checked for pinched wires?

 

Did you disconnect the old module?  Just unplug it, up by the fuse box.  It needs to be disconnected for the new one to work right.

I haven't troubleshooted any of that, I'll definitely do that tomorrow. Thanks so much.
 

Also I've seen two different diagrams. The one I posted earlier and this one. Not sure which one is correct one for me follow,  using a stock 1978 with L28e, harness and everything.

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Edited by TakemuraShuu
w

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The diagram in the first two posts is the correct one.  The pickup coil in the distributor "signals" the module to fire the coil.  The ECU is not involved.

 

Your second diagram is for the system where the ECU controls the coil.  That did not come until 1981 with the 280ZX turbo engines, and the ECCS system. 

 

Yours is actually pretty simple.  A few checks with a meter should find any problems.

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On 12/19/2018 at 6:27 PM, NewZed said:

Have you checked the B pin for voltage?  Checked the red and green wire's resistance, through the distributor's pickup coil?  Checked the resistance of the coil's primary circuit?  Checked for pinched wires?

 

Did you disconnect the old module?  Just unplug it, up by the fuse box.  It needs to be disconnected for the new one to work right.

 

You have wires connected but haven't confirmed that things are correct.  A picture isn't really going to help.  Good luck.

 

B - 11.79volts
C - 10.52volts
W - 5.89volts
G - 5.89volts
Hmm, think maybe the ground isn't good enough? Also when the key is in the on position, I hear a faint whining sound coming from the HEI module. Thanks again for the help!

 

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Your voltage readings are odd.  With the engine not running you should not see any voltage on G or W.  Maybe you're taking the readings in the wrong way.  Your B and C readings seem to show a damaged circuit also.  With the engine not running they should be reading the same, battery voltage, if the key is on.  If the key is off they shouldn't show any voltage.

 

When you post voltage readings it generally helps to tell where you put the probes and if the key is on or off.

Edited by NewZed

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My apologies, the readings I recorded were taken when the key was in the on position. I just recharged the battery and the reading were about the same, the battery's voltage is around 12.70, while B is 11.70ish and C is 11.34. I'm positive I followed the diagram correctly as well as grounding the module properly, do you think I could've blown the module somehow?

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Might be that it's damaged.  I can take readings on mine in the next day or two.  Out of town right now.

 

You still didn't tell where your probes were.  Sometimes people measure along a circuit instead of to ground.  I can't match your readings unless I know how you took them.  The B and C difference implies that current was flowing, when it shouldn't be.  The module has an automatic shutoff feature.  

 

I'm not an expert so somebody else might have some thoughts.  Feel free to offer.

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On 12/25/2018 at 3:31 PM, TakemuraShuu said:

My apologies, the readings I recorded were taken when the key was in the on position. I just recharged the battery and the reading were about the same, the battery's voltage is around 12.70, while B is 11.70ish and C is 11.34. I'm positive I followed the diagram correctly as well as grounding the module properly, do you think I could've blown the module somehow?

did you fix your problem?

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Hey TakemuraShuu, I know this is a really old thread, but I came across this when I was struggle trying to do the same. I just wanted to throw this out there, if someone else goes down this path. This post was helpful. 

 

I was able to get the spark to work. I put the signal to post "W" and grounded "G". And just tidbits for disclosure, Im using a 0v type 4-pin HEI module, and I'm running things on the bench with Speeduino. Just something to consider. 

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