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76 280z Fail! help please.


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      I’m super embarrassed and I need some help. I bought a 76 280z a couple months ago. The first thing I decided to do was restore the dash. After I was done with the dash and put it back in the car it wouldn’t start or crank just nothing. I realized I mixed up the two red wires on the battery terminals and I figured that was a real bad thing. So I replaced the main relay thinking it burned out when I did that but still nothing. I’ve read the wiring guides over and over and taken most of the harness apart to see If I could find any thing. I thought it might be some safety or security thing so I’ve tried to hard wire a few of those and still nothing. I know the starter works because the guy before me put a direct button start on it and the car ran fine before I got my hands on it. Is there some way to hot wire it or make it start with some kind of switch system? I really don’t care about looks I plan to do a v8 swap and track the car at some point. It would just be nice to be able to drive it around for now. I have no idea what stupid n00b thing I did, but any help would be great. Thank you for your time and I cant wait to be apart of this forum!

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I've checked and rechecked that things are plugged in. I've even put the harness in with out the dash just in case some thing was hiding. I just plugged every thing back in and only the dash and heads lights come on. It doesn't help the guy before butchered a lot of the wiring in side the engine bay too. Huff I blame gremlins x_x

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The two heavy red wires carry the power to the ECU for the fuel injection and a couple of other things including one of the multiple relays that control the fuel pump.   


It is confusing that they are both red.  One should be connected to the positive post of the battery.   The other is actually a ground and bolts to the firewall near the battery.   Both usually have a fusible link near their termination point.   I have no idea why Datsun decided to make them both red, probably so they only had to buy that gauge of wire in red for the harness.  And maybe it was convenient to have both fusible links located close to the battery.


The lights, ignition switch, and instruments are not powered by those two wires.  (maybe the tachometer is, I forget).  The fusible links you pictured protect the other items on the other harness (excluding the ECU harness itself).


The harness on the driver's side is for the EFI primarily.  It does contain the temperature sender wire and If I recall correctly the AC power line


But, it has been years since I worked with a 76 280Z, so my memory could be faulty.   Hopefully, my reply will help out a bit.

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I was able to figure that out after I followed both red wires all the way threw the harness. I guess every penny counts to datsun :/. Could I have fried the ECU by switching them up? If there's any one in the New Mexico area that would be willing to help me out I'd gladly buy them a beer or two haha!

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1.  turn the ignition switch to ON postion. 

2.  disconnect the wire that has the blue connector.  Your on your car is probably a different color. Im just using color to point out its location.

3.  Use a screwdriver to bridge between the big red wire connector to the connector where the blue connector was.


4.  does it crank over?



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I had a feeling some one would say that.. But really I traced the whole harness and tried every other thing in the book and still nothing. I've made sure to be a thousands times more careful with the donor cars harness and label every thing clearly. Failure is the secret to success so I just need to learn from this ;p but thank you again for your time.

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