I have had a no spark issue for a while now with my 300zx, it began after I did the fuel pump relay mod because I put in the Walbro 255lph fuel pump, the car did receive spark a few times but after a few weeks of trial and error, the spark completely went away. Yes, fuel is injected when I crank the car, and I have replaced the ignition coil, crank angle sensor, ECU (ECU diagnostic lights don't turn on in the original ECU, and the replacement ECU doesn't have diagnostic lights so I couldn't test it), and I did the PRW-2 mod and nothing fixed it. I am out of ideas, any suggestions would be appreciated.

Not familiar with the "fuel pump relay mod". Maybe you blew a fuse. Have you used a test light or meter to check for power at the coil with the key on?

Do you have the service manual? You can download it here, linked below. The ECU has diagnostic trouble codes through the lights. Open the EFEC chapter.

https://www.classiczcars.com/files/category/15-300zx/

Continued...

The fuel pump relay mod is basically when you rewire the fuel pump to an aftermarket relay in order to hardwire the fuel pump to the battery because the new fuel pump requires more current and would possibly damage the ECU if you used standard wires. And yes I checked the ignition coil wire and the positive side gets 12 volts. I also tested the ground side while cranking to see if the voltage would go up and down, and it didn't, meaning that the ignition coil isn't even getting the signal to turn on in the first place. And I cannot check for diagnostic codes because the lights bulbs on the ECU don't turn on at all.

Edited April 1Apr 1 by alexiscastro221

25 minutes ago, alexiscastro221 said:

I also tested the ground side while cranking to see if the voltage would go up and down, and it didn't, meaning that the ignition coil isn't even getting the signal to turn on in the first place.

Actually this could mean that the power transistor or the wiring is bad. No offense but can't tell if youre using twists and electrical tape, or crimps, or soldering. You can check the control wire from the computer directly at the power transistor connection. That will tell you if the computer is controlling the power transistor.

I'm not sure which of the three wires is the control wire. But you can see from the circuit diagram that one pin is ground, one is battery voltage with the key on, and the other is the control wire from the computer. I think that it might be a 5 volt square wave, which should flash a test light, I think. That's what I would test. That tests the computer directly. If you are positive that injectors are squirting that means the computer is getting what it needs. You'll want to be sure the injectors are squirting, the computer won't squirt or spark without the right inputs to the computer from the distributor.

At the PRW2 connector frm the computer, ID the ground, ID the battery power, the one that's left is transistor control. Test it for flashing when trying to start. It might even show 5 volts, off and on, if you turn the engine by hand with the key on. Not sure.

@cgsheen1 has expertise with the ECCS's. He might have some thoughts.

Hmmm, yeah makes sense. Even though I upgraded the transistor (and I used heat shrink crimps by the way, please correct me if I shouldn't have) to the z32 transistor, it is also still my main culprit. I'll check out the wires and do the tests you told me to, thanks for the advice.

On 4/1/2026 at 4:31 AM, Zed Head said:

Actually this could mean that the power transistor or the wiring is bad. No offense but can't tell if youre using twists and electrical tape, or crimps, or soldering. You can check the control wire from the computer directly at the power transistor connection. That will tell you if the computer is controlling the power transistor.

I'm not sure which of the three wires is the control wire. But you can see from the circuit diagram that one pin is ground, one is battery voltage with the key on, and the other is the control wire from the computer. I think that it might be a 5 volt square wave, which should flash a test light, I think. That's what I would test. That tests the computer directly. If you are positive that injectors are squirting that means the computer is getting what it needs. You'll want to be sure the injectors are squirting, the computer won't squirt or spark without the right inputs to the computer from the distributor.

At the PRW2 connector frm the computer, ID the ground, ID the battery power, the one that's left is transistor control. Test it for flashing when trying to start. It might even show 5 volts, off and on, if you turn the engine by hand with the key on https://vegasnowcasinoauss.com/. Not sure.

@cgsheen1 has expertise with the ECCS's. He might have some thoughts.

Good point. At this stage I'd probably focus on the transistor control signal too. If the injectors are firing, the ECU is seeing the distributor signal, so checking for a pulsing signal on the transistor control wire while cranking should help narrow it down pretty quickly.

Edited June 29Jun 29 by devidevighst

10 hours ago, devidevighst said:

checking for a pulsing signal on the transistor control wire while cranking

What would you use to check for a pulsing signal?