NicholasKoenig

I didn't check for continuity, does that mean, red probe on E and back to vehicle ground? What would the results be? Still learning these terms as I make my way through electronics. Ok, thanks for the reassurance. Hopefully CO and I can plan something soon and try his loaner.

After reading this I couldn't wait. Opened the Z back up with flash light in hand. I used my dmm on the E and C legs of each transistor, key on. They both read 12.15V! Now I'm confused, I thought for sure this was the issue.

I had a suspicion it was a replacement because when I took off the metal box shell, there was already one screw missing, one that secured the green electrical plate down. The K11-600 000 sticker is on the outside of the box and another exact one on the inner workings of the ECU. The connections on the transistors looked together, they didn't seem broken after my once over look. I put it all back together and started up the Z. Unfortunately the symptoms remained exactly the same. It started right up though! I put my ear to the injectors and confirmed again that only the rear bank is working. This brings me to another question. If this ECU was replaced, am I just unlucky or is there something else that has caused at least two ECUs to fail?

Awesome. I'm in NE Philly myself. Took the ECU out to get some photos and take a peak. I don't know what I was expecting but I popped it off and instantly realized I have no idea wth I'm looking at haha. Nothing seemed loose or disconnected. Maybe some dirty stuff that built up by nothing stuck out. The transistor connections looked ok but they still may be at fault for all I know. ECU Part # K11-600 000

Thank you. I predict I'll pop the cap off. Wiggle some stuff and stare at it for a few minutes. Pack it all together and see if it starts again! Im on the cusp of getting all 6 cylinders to fire, I can feel it. Can't wait to hear what it sounds like when all of them actually fire. Nearly had the Z one month!

Hey, thanks for the outreach. I will keep that in mind as I'm definitely heavily considering getting another ECU anyway. Not selling myself short but I have some reservations on my ability to fix the ECU and have it remain fixed haha. Edit: I'll be able to take the ECU # down tomorrow for sure

Thanks I went through the thread. Part # for the transistor is "NTE247", for the convenience of any readers out there with a similar situation as myself. Now I know what it looks like, I'm actually exited to take out the ECU tomorrow and see what is going on in there. Attachted picture for reference.

Although I'm new to Zs, I've already done some shopping around for parts and what not. I too noticed their prices are jacked. That considered, once you deduct the 200$ core charge, the re manufacturered ECU comes to $125. And that is cheaper than other remans I've found which seem to go for 200-250. Thanks for the classified tip!

It's worth a shot, although I wouldn't really not what to look for. Burned connections, corrosion? I'll take it out tomorrow. Could you send the part #? May be a better alternative in my situation as you mentioned.

Gotcha. This is a relief because I am likely close to the solution instead of scratching my head at this. Id rather not buy an ECU from eBay, they are cheap but probably risky. I saw this one available, once the core charge is accounted for it seems like a good deal ($124). Any vendors you guys recommend for an ECU?

Hey guys, thanks for the replies. I just got done using my dmm on the ECU pins. Injectors plugged in, key on; all six injectors read 11.92V!!! Does this rule out my harness and point to the ECU?

Turns out I have a similar attachment to yours. Instead mine is soley for the 1976 EFI trouble shooting instead of the broader range of yours. But looking through it helped me find the name of the black Bosch part i was questioning. It's the fuel injection relay. (Photo attached) Perhaps this Bosch replacement is faulty. Which leads me back to the harness that was retapped under the dash. Maybe that's hiding some shoddy soldering work or other gremlins.

Ok I'll go through the ECU pins again tomorrow after work. I only get about an hours worth of tinkering each day max so process is slow going. Yes, looking through the FSM wiring diagrams I have saved, it looks like the the first four injectors connected to one dropping resistor and the remaining 2 are on the other resistor. From this I think it's safe to assume my dropping resistor is functional. Otherwise, only four or two cyclinders would fire by My logic and understanding of the diagram. And since it gets fuel, spark, and air with working injectors, the only thing left is faulty harness (the first 3 injector wires) or ecu? Going to look over your attachment now. Ill let you know how I do with the multimeter tomorrow!

The previous owner said it "ran 2-3 months ago" from the time I bought it. To my knowledge his son was wrenching on it and his work seemed lack luster but it appears as though he didn't alter any of the presumed electrical issues im experiencing rn. I reversed the bank connections. Placing the rear bank (the functioning one) onto the front and the front onto the rear. The front injectors began clicking and rear were silent. To me this rules it electrical but to what extent? Is it a wiring issue or something like the dropping resistor or ecu? Another thing I noticed, the part of the EFI harness that is in the engine bay looks untouched. But under the dash you can see electrical tape around the harness (didn't look that fresh but def not stock). That led me to the fuel / afm relays. The stock wires plugged into a Bosh black box that looked modern ( I doubt Japan used Bosch in the 70s?). Is this a clue? It seems like the harness is the issue but I don't want to mess with anything I don't need to. I'm learning along the way and any advice helps. Thank you for the quick reply.

Recently bought a Z and am sorting out the issues. It runs albeit on the 3 rear cyclinders. New fuel pump, new NGK wires and plugs, distributor looks like it was replaced not long ago. Coil looks original (new MSD blaster in the mail). I know it's getting fuel, spark and air. I know all 6 injectors are functional. Just not all at the same time. When I crank it, it starts almost instantly, when I place my screw driver to each injector, only the rear bank makes the clicking. Removing any of the front 3 injector pig tails doesn't affect idle. When i place the rear 3 injector connections on the front 3, once again it starts and idles the same. Is this a fault in the first bank wiring harness? A dropping resistor issue, faulty ECU? Currently I only have the FSM available on my phone and I'm diving through it but I feel overwhelmed. I checked the pins with a multimeter and each injector is getting current. Did I miss something simple? Thank you for reading. Hope to hear from you guys soon. PS, I bought all new injector connections, but that doesn't seem to be the issue despite them being worn. Haven't installed yet.