NewZed

Have you checked each injector's circuit? Power supply and continuity back to the MS board? If you have power supply and connection on the grounding side on all injectors at the board then your thought that the board is messed up is probably right. You probably know this but the injectors spray when the computer supplies a ground to the injector circuit. Voltage is always present at the injectors when the key is on, but they only spray when the circuit is grounded and current flows through the injector solenoid. There are several ways to check the circuit. At least you're making progress. p.s. the engine still should have started, then died, with ether. You might still have a problem after fixing the injector situation. One problem at a time though...

p.s. forgot one of the other big EFI problems that often catch people - intake system air leaks. Leans out the mixture and also kills the sensor signal to the computer. The computer adds fuel based on the air flow it is told is happening. Might even be a bad MAP signal. Signaling no air, meaning 'no fuel necessary". Or a shorted temperature sensor showing a hot engine, which also means less fuel needed. I'd go through the whole cold start sequence and look at what the computer needs to know. Make sure it's getting good information.

I would try starting fluid again. It's not satisfying as far as puzzle-solving, it feels like cheating, but it really will tell you if the spark is happening at the correct time, and the intake system is open. If you have a remote starter and a can of starting fluid you should be able to run the engine for minutes all by yourself. On a cold engine it's not a big deal, it won't hurt it. On a warm one you can get some detonation so don't overdo it. Beside that, don't overlook the exhaust side. Any chance the exhaust system is blocked? The air has to be able to flow all the way through. You said all you did was install a turbo. Turbo is part of exhaust.

Here's a basic that often catches people - maybe you have the ignition timing set to the exhaust stroke. The flash of your timing light. The timing mark on the damper pulley passes the pointer twice - once on compression and once on exhaust.

If you have spark and timing is right it should start on starting fluid and run for a second. Not just a sputter but a solid burst of RPM. Any chance you left a rag in the intake tract? Could there be a blockage somewhere? Are you using a MAP sensor? Have you had a spark plug out and rechecked it? Maybe you're adding too much fuel and gas-fouling the plugs. Those are big injectors. Just some ideas. Get back to the primitive aspects of the engine. Fuel, air, spark.

It might help to describe more about the engine itself. When did it last run? Have you done any work on the engine? Your focus is on the MS system but maybe it should be on the engine.

Any chance that you have the plug wires installed in backward rotation? That would give proper timing on #1 but the others would be off. Although, I have started an engine with the plug wires that way. It ran terribly. Here's your old thread with the msq file.

The power to the chip would come through the trace on the board. It's hard on the eyes but you can follow the trace back to its source. You might find a burn mark or a cut. The board might not be ruined if you find something. People repair circuit boards. If you put the board together yourself then the odds of a wrong/bad solder are higher, I'd guess. I'd go back and check my work. By the way, you can buy inexpensive transistor testers. No idea which are good or not. Even Harbor Freight's cheapo multimeter has one. Really though, if there's no power on the board trace even a good transistor won't work right. Not an expert... Just for fun - https://www.harborfreight.com/electrical/electrician-s-tools/multimeters-testers/7-function-digital-multimeter-59434.html

How are you measuring power at the transistor? Are you probing the board? Did you pick the correct pin? You're in to electronics world now. Here's a couple of links that might help. I've never been in to a Megasquirt board I'm just commenting based on the basics. Maybe you'll see something in the diagram. There's a fuse or two but it seems like the whole unit would be down if it blew. Maybe the BIP373 is damaged, although they say it's very durable in the link I gave above. But in their chip upgrade, linked below, they call it "infamous". Who knows, their description above and the link below are kind of contradictory. Good luck. https://www.diyautotune.com/support/tech/other/grounds/ https://www.diyautotune.com/product/coil-driver-kit/

It's not the votage drop that matters it's what the voltage drop indicates. No spark will be created if the current through the coil is not stopped. You could also disconnect the coil negative at the coil and check the wire for continuity to ground, key off. Disconnect the wire, put one meter probe on the end and the other probe on a good bare piece of metal or the engine block. You should get OL or infinite/huge ohms on your meter.

Here's some BIP373 stuff in case you haven't seen it. It will shut down automatically if settings are wrong. They give some quick and dirty settings also. https://www.diyautotune.com/support/tech/other/bosch-bip373-ignition/

I don't know much about TunerStudio but can you see the coil control signals? In other words does it show that the current is being turned on and turned off? That's what causes spark, the turning off of the current. 11.9 volts is low, implying that the negative side of the coil is grounded. But it should only be grounded through the Megasquirt circuit, no other circuits. You might try disconnecting the connection to Megasquirt and seeing if the coil still has a voltage drop. You might have a short to ground on the negative side of the coil. With Megasquirt disconnected from the coil the voltage should match battery voltage exactly since no currrent is flowing. The other thing connected to the coil negative is the tachometer trigger. A shorted tachometer could cause the problem, for example, although that is unusual. You didn't confirm that the old igntion module is completely disconnected. If the blue wire from the coil is accidentally grounded it will cause a problem like yours.

Probably in the manual. It's both 700 and 3000. Good luck. https://static.summitracing.com/global/images/instructions/xr700 instructions.pdf

You shouldn't need to snip the resistor for the tach. Might actually be a bad idea. Just disconnect the original module by the fusebox and leave the blue wire connected at the coil so the tach can count sparks. somebody on another forum just had a similar problem. They forgot to disconnect the module but after they did everything worked fine with the resistor on the tach line. Have you looked through the several installation articles out there? I think that the swap to the DIY CAS wheel just make things more likely to work correctly. "More friendly" as DIY Autotune says. Something to keep in mind if you have problems. Good luck. Post a startup video. https://www.diyautotune.com/product/54-mm-optical-trigger-wheel-for-nissan-l28et-or-vg30e/ https://forums.hybridz.org/forum/93-megasquirt/ https://www.diyautotune.com/support/tech/install

There is no swap hardware to put the Z transmission behind a V8. It wouldn't handle the torque anyway. The 260Z engine is about 158 cubic inches, compared to 350 for a SBC. The old Z transmission bearings are typically ready to fall apart besides that, not uncommon even with the stock engines. It would probably last about one pull. I haven't done it myself, but I wouldn't even try it just based on what I've learned.