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73' 240z ballast resistor removal


spoolin4life

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Hey folks,

So I'm trying to sort out a multiple cylinder idle misfire on my 73 240z. I've replaced everything in my ignition system. (Coil, plugs, wires, distributor, distributor cap, ignition module, rotor) the problem still persists. I did a spark test and I have a weak spark across 4 cylinders. 3 and 6 are best but still even weak.

I'm on a msd blaster 2 ignition coil with a 280zx distributor. I've deduced that either I have a lose ground somewhere or the ballast resistor needs to be removed to use the coil I have optimally at 12v. I still have the same problem with the old coil as well.

So I'm curious and tried to find the answer online but on my ballast resistor I have 2 wires. One is black and white, the other is green and white (although the white on both looks yellowish). Can I connect them or do I need to connect them to somewhere else?

Thanks for the help. I've read the writeups online and none seem to match my current coloring 

Screenshot_20210807-222234_Video Player.jpg

Screenshot_20210807-222537_Video Player.jpg

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Check the ground from the module itself to the distributor body and from the distributor body to the engine ground.  The ignition module needs a good solid ground so that it can pass the current needed to charge the coil.  Most distributors have their own ground wire terminal, not sure if the ZX's did.  A black wire from ground to distributor body.

You don't need the ballast resistor but with that coil you should get better than you got with points. 

You could also have problems inside the distributor.  They are known to break their stator magnets, and/or have the shaft bushing go bad causing air gap problems.

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14 minutes ago, Zed Head said:

Check the ground from the module itself to the distributor body and from the distributor body to the engine ground.  The ignition module needs a good solid ground so that it can pass the current needed to charge the coil.  Most distributors have their own ground wire terminal, not sure if the ZX's did.  A black wire from ground to distributor body.

You don't need the ballast resistor but with that coil you should get better than you got with points. 

You could also have problems inside the distributor.  They are known to break their stator magnets, and/or have the shaft bushing go bad causing air gap problems.

I actually have two 280zx distributors I tried it on with 2 modules and I had the exact same misfires on the same cylinders. So it has to be a ground somewhere not sending the proper output to the coil. 

I'm not sure the coil will work well with the resistor mind you. That's why I'm curious. I'm getting spark it's just very weak. Oddly though the module must prioritize cylinders 3 and 6 as they fire back to back in sequence and they're the strongest 

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2 minutes ago, SteveJ said:

Yes, I bypassed the resistor in my 260Z that has a ZX distributor. I have done the same in my 73 with a Pertronix, though I haven't fired it up since I put in the Pertronix.

Same colors? I don't wanna burn the coil or start a fire haha. Thanks though 

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51 minutes ago, spoolin4life said:

So it has to be a ground somewhere not sending the proper output to the coil. 

You write very confidently, but the statement makes no sense.  Grounds don't send outputs.  And the video was neat but no idea what it was meant to show.  I saw a good spark.  The engine sounded pretty smooth for 5 cylinders.

Lots of other things can affect individual cylinders.  Valve lash, valve sealing quality, compression, bad plug wires...

Good luck.

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1 hour ago, spoolin4life said:

Are you absolutely sure they can be connected? I can't find a wiring diagram to confirm their outputs and such. 

The wires are already connected.  They attach to the same piece of metal.  Nissan used the ballast resistor as a convenient place to create a terminal block.

image.png

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23 minutes ago, Zed Head said:

You write very confidently, but the statement makes no sense.  Grounds don't send outputs.  And the video was neat but no idea what it was meant to show.  I saw a good spark.  The engine sounded pretty smooth for 5 cylinders.

Lots of other things can affect individual cylinders.  Valve lash, valve sealing quality, compression, bad plug wires...

Good luck.

I meant to say loose wire. I'm half asleep here lol. Although this stuff is not my expertise by any means. I have done a compression test and the engine is almost 180psi across all cylinders except #3 which is 168ish. So it should be strong. The spark looked very intermittent to me. Whenever I've tested spark in the past it's a very loud snap and never misses like it did in that video. Also there's no audible change on some of the cylinders when I pull their wires. The ignition system is pretty much all new components aside the rotor which was done last year. 

I appreciate the help all the same. 

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12 minutes ago, spoolin4life said:

I meant to say loose wire

Can't really find a place to put "loose wire" and make sense.  Re-read the thread tomorrow after some sleep and see what you get out of it.

"So it has to be a ground "loose wire" somewhere not sending the proper output to the coil. "? 

Still doesn't work.  Loose wires don't send outputs either.

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