from your parts 300zx, take out its ecu and harness and install it in the 280. much better programming and it will run fine. sounds like your ecu injector control is not working for whatever reason. i agree with the cold start valve making the engine run. grab a bulb tester and check the wiring like the fsm says when cranking. if you want to keep is running to check, wire the cold start valve to battery like the fsm says to release pressure, basically hot wire it, and see if it stays running so you can diagnose the rest. the cold start wont provide enough fuel to rev, but it should idle

 

I would use the 300zx wires and ECU but all those parts cars had fires under the hood.

I did do the 9 volt battery test and the injectors click and the pressure drops. So I know the injectors are good. It all comes down to the ECU not firing the injectors. We are going to double check all the wires to the sensors. I'm still looking for another ECU.

 

We tried wiring the cold start valve on and it started and ran. Actually got the RPM's up to 3000. We tested every signal input and wire to the ECU and now know for certain it's a ECU problem.

Still can't find a ECU for a 83 5spd NA

 

too bad your not closer, i have several 82 ecu's and i just pulled the entire harness and ecu out of my 79 that you could stuff in there and it would run well

 

I wonder what it would cost to ship it to us? Our zip is 46069.

 

prolly 40-50 or more. the border makes parts sales almost not worth it for the buyer. i even have 82 harnesses in my loft i could find as well.

 

I have found the problem. It was not easy to find.

I have a shorted fuel injector. Not shorted to ground rather pin to pin. It's on cylinder # 5 and was causing the ground going to the injectors to not be useful. Reading across the injector I was getting 1 ohm and it should have been 3 ohms.

It was only discovered after I was about to give up and started disconnecting injector wires and testing voltages. I had the back 3 off and tried to start it and if fired up, although ran like **** it stayed running. The first time it had ever done that. I started reconnecting the injectors one at a time and when #5 was plugged in it started to die.

BTW I also discovered something everyone should take note of. If you have a car that will start and run for 2 or 3 seconds it means the ECU is not firing the main injectors. In fact you can pull the ECU out of the car and it will do the same thing. This is because the cold start valve does not use the ECU, rather the thermotime switch, and will inject fuel for the length of time the key is in the start position. Further more you can wire the cold start valve to 12volts and start the car, it will run up to about 3000RMP.

After I got my car to run, (I left the bad injector unplugged) believe it or not the clutch was stuck on all the time. I drove it around for 2 or 3 miles gunning it with the clutch pushed in until it finally broke free. I had to start it in gear and rely on my exp. driving a big rig to shift without a clutch.

Thanks

Chris

 

cool info for anyone having the same sort of issue to check. funny how its always the last thing you check!!!

 

hello have you tried to clamp off return fuel line next to filter to keep up fuel press you obviosly sound like you have fuel flow worked for me today good luck

 

I need to update this thread. I thought I'd found the problem and put the car in storage for 2 yrs. We just got it out and again it was not running. Had the exact same issue as my OP.

So once again I pulled the plug to the injectors one at a time. When I got 1 or 2 unplugged (didn't matter which ones). the car would start.

Playing around with my meter I discovered some strange voltages. I decide to supply my own ground to the ground pins on the ECU. Like magic it started right up and runs strong. My best guess is the ground screw to the frame is rusted or corroded. I'm not sure where they ground the ECU to the frame so I soldered my own ground inside the ECU.

Now the car starts almost instantly with all injectors pulled in.

We are going to repaint it and drive the wheels off it. lol

 

Grounds grounds grounds.... the source of many an electrical nightmare. Also one of the reasons I highly recomend running a ground directly from the battery to the ECU and from the same lug to the ECU to the plenum where most of the sensors are.

 

FricFrac, The ground to the ECU, how did you apply the ground, some means of connecting a lug to the metal housing?