Have you checked the harness for 4,5,6 with a noid light?

negative, The notes I got from the mechanic said he checked. He mentioned that he could get voltage at the ECU but could not get it at the injectors. Even with the three injectors that are working. He thought it was strange.

There are 2 resistor modules located next to the clutch master cylinder that are in that circuit iirc. Lift up the inspection lid and check those connections

I'd want to know what shape the engine was in before buying the power parts. A set of used injectors might be worth the money just to get it up on all six for a thrashing. Or having them cleaned and verified. A set of cleaned and verified injectors with documentation can probably be easily resold after your upgrade.

There could be other reasons that the back three aren't combusting. The testing that's been described is pretty weak. No voltage seen, no noid lights, etc. And, on the tapping, you need something hard that causes a high frequency shock. A rubber mallet is not enough.

Good luck, looks like fun.

https://www.ebay.com/itm/187699479261?_skw=280zx+injectors

https://protunerz.com/collections/intake-manifolds/products/l-series-intake-manifold-fuel-rail-75mm-throttle-body

https://protunerz.com/collections/intake-manifolds/products/datsun-l-series-intake-fuel-injector-adaptors-14mm-11mm-1

That’s what the idea was, get some super cheap used injectors to assess other issues. I don’t really want to buy new injectors only to replace them in a couple months. I may bite the bullet on some Amazon injectors.

At some point I’ll also buy the engine/fuel management system as well. I’ll wait for an engine rebuilt for that.

As far as the engine goes, when I scoped it, the cylinder walls looked great. It burns some oil sure. Mechanic said compression was low which is fine. Now I have more data about the condition of the motor.

I bought a Noid set, so I’ll wait for those to show up.

You can trace it down with the noid light. Did you check the resistor packs I mentioned? Could be corrosion which would explain those 3 right together. Oddity that it’s that bank connected to those 3 injectors. Definitely would check that first

Not yet, I’ll check it out in the morning when it’s not so hot.

Check the efi bible to verify but you could swap the packs if you don’t find corrosion. You will find out quickly if 123 stop and 456 fire. Just a thought

Yarb's EFI Bible comment is on target. You've already tried the quick stuff. You can check power through the injectors at the ECU connector. You can even ground them there to see if they open. If you don't have power at 4, 5, 6, then new-used injectors won't help.

https://www.classiczcars.com/files/file/32-efi-book-1980/

I got really bored so I went out.

Those resistor modules are a pain to get to lol! I got to it but I decided to try a little experiment. Since I knew the back three didn’t work, I swapped one of those leads to a know working injector. The injector fired with 2 of the three lines. The third I believe has a busted pigtail since I see exposed wire.

Logic would tell me that signal is indeed reaching the injectors.

btw, did you know that not only will this engine run on two cylinders but also 3 with a jank firing order lol.

I think I understand what you said but can you try that explanation one more time. Did you swap the resistor connections as I suggested. You’re jumping around a bit. We’re trying to delete variables one at a time. First was to make sure both packs were good and clean connections to take that variable off of the board. Results from the suggestions we make determine which direction to go from there. If possible write down the results from each test. Hard for us to go back in the thread and review each step your taking without stating it here.

Yea, so I went to swap the plugs on the resistor but I couldn't because they were different size plugs. Visual inspection of the resistor(s) itself showed that they were not equal in size. They had rubber covers over the connectors but I was able to pull them back and they looked like they were in decent shape.

So I went to the injectors and pulled the pigtails off the back three cylinders (4to6) that weren't firing.

While the car was running,

I pulled a pigtail off the 3rd cylinder causing the engine to drop to 2 working cylinders and installed the pigtail from cylinder 4 into cylinder 3's injector.

I used my magic tube of enhanced hearing and heard the injector 3 firing with the pigtail from cylinder 4.

I changed the plug again to the pigtail from number 5 and same thing. good so far

When I plugged in the pigtail from number 6, I got nothing. On further inspection of that plug, One of the wires right at the plug was exposed, frayed and had some corrosion. (I've already have a new set of pigtails on order)

That tells me that signal is getting all the way to the injectors and the only other item left in the line is the injector itself. At least on 5 cylinders anyway.

I'll see about making a video in the morning to clear it up some more.

Edited June 13Jun 13 by nowak1981
reworded