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J Taylor

Car gets no spark until you let the key go.

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STILL trying to troubleshoot my 280z turbo. The car has been running real rough and won't make any boost. I have checked everything you can name. I finally swapped in a new turbo wiring harness last night and now the car won't even crank. If you pull the coil wire off and crank it it gets no spark until you let off the key, then it gets one big spark. With the coil wire on, same thing....car won't crank until you stop cranking, then it gets that one spark and you hear it try to fire. ANyone got a clue what the problem could be?



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Guest greimann

What you describe sounds like something is not triggering the coil to make and break the circuit in concert with the crank rotation. When you hit the key you charge the coil and only when you turn it off does the field collapse and cause the spark. Check reluctor, capacitor, module and associated wiring.

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Check the little ignitor thing that goes between the coil and the wiring. Not sure what it is called, but it has two wires going into it. Yeah I know that helps. It should be connected to the coil bracket on a stock coil.


I have some "creative" wiring done on my 260 that I am going to have to fix, and evidently it must have had the same problem, because the previous owner "fixed" it. I have a replacement harness that I am going to put in and see if I can't get it wired back properly. when I get around to it, I will let you know what I find.


Oh yeah, I forgot, you do have the one yellow wire that connects to the harness down by the ecu connected and run to the coil right? That would keep it from firing.

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I forget where that yellow wire is going but it is to the same place it was going on the old harness. I put the 2 harnesses side by side and made the same changes to the new one that the old one had. Here is one thing I found after messing with it for a while. On the pass side part of the harness there is a relay. If I mess with the relay(pull it in and out while cranking) the car fires. I can turn the key to the on position and everytime I touch the relay to the plug the coil wire sends out a spark. I dunno if this is normal or not but just an observation. I have pulled the harness back out now and trying to decide if I want to go ahead and start installing the SDS. I really hate to do it not knowing if the wiring is my orginal problem or not but that is about my only option except for towing it 3 hours and dropping it off with Ira.

You arent the same guy that has the black 280z turbo are you? The one that used to have stripes.


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NO that is Paul, and I am supposed to help him install the JWT set-up, but I don't think he is ever going to pick it up from Ira.


I wonder if you are not having a problem with that relay since the car fires when you mess with it. You also have the wiring for the fuseable links over there too. I wish I had my copies of the harness, but my bud has them. I guess I need to get them back.


I would get the harness problem situated. No sense chasing a ghost when you start with the SDS. You really need a factory manual so you can test the components.

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Well, I'm not really familiar with what harness is required in a turbo car where that car was not a factory trubo car to begin with.


But, I do have a Factory Datsun 78 Manual. Its Ignition Chart has the powerflow as such:


Power begins at the,


1) Battery, from the + Post, to the

2) Ignition switch, from the Ignition switch

3) The circuit splits into two wires: Both of these are "Black & White" wires, from the split

4) One "Black & White" wire goes directly to the + side of the coil

4a) The other "Black & White" wire goes into the Transistor Ignition Module, which

5) Powers the Transistor Ignition Module


*NOTE: From the Picture of the Transistor Ign.Module there appears to be 4 separate control functions:

a) Spark Timing, Signal Monitoring circuit

B) Lock Preventing circuit

c) Duty Control circuit

d) Power Switching circuit


It is the a) Spark Switching circuit that exits the module & attaches to the - (negative) side of the coil: this wire should be a "L" color; I'm guessing "L" means Light Colored(?).


6) Then there are two other wires at the Transistor Ign.Mod: "Red & Green"

a) One: one wire coming from the distributor

B) Two: one wire going to the distributor

*NOTE: The book is kind've confusing on how the "Red" or "Green" wire is hooked up to the distributor: it merely shows a terminal block at the dist. PERHAPS IT IS THIS TERMINAL BLOCK THAT WAS HOOKED UP BACKWARDS; interupting the polarity?


And that is it. The book doesnt go into detail about each circuit; simply shows the diagram.


I would venture in guessing that, in your harness replacement, you either crossed a wire to the ignition switch or crossed a wire going to the Transistor Ign. Module.


A final guess could be that:

1) the ignition switch has failed

2) the Transistor Ign.Mod. has failed or

3) one of the components has failed & you also may have crossed a wire in your installation of the new harness.


Hope this helped.



(Yea,Still an Inliner)

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