Recently bought a 1984 AE Z31 and it ran for a few weeks and stopped after sitting in traffic and wont start up again. I think it has to do with the fuel system as my fuel pump is constantly priming and wont shut back off. I've changed the relay, fuse, filter, and the pump itself and the new pump is doing the same thing. Also my fuel gauge has almost no power to it, except the orange light above it being on. Really need help on figuring out this problem.

 

Have you done the usual tests?

1. fuel pressure
2. spark/spark plug condition (gas, etc)
3. Error codes (ECU)

Tests for error codes in a 1984 Z31:

1. Turn the ignition switch to the ON position.
2. Turn the ECM diagnostic mode selector on the ECU fully clockwise.
3. Wait for the inspection lights to flash three times (one after another).
4. When you see the three flashes, turn the mode selector fully counterclockwise.
5. Count the number of flashes. The red flashes represent the tens digit, and the green flashes represent the ones digit.

Sample error codes:

Code 11: Crank Angle Sensor (CAS) is not giving proper signal. (One red and one green.)
Code 12: Mass Airflow Meter (MAF) may have issues, such as a corroded connector or broken wires.
Code 23: Throttle Position Sensor (TPS) might not be calibrated properly. Check the condition of the wire/connections as well.

Fingers crossed for you.

 

I have confirmed fuel pressure, plugs were a little dark so I changed them. I already checked and fixed all the codes my ECU gave me. I also replaced the TPS and the CAS. Unsure of what is causing it to not start. Going to test that spark is getting to each plug later today.

 

Have you tried checking the fuel pressure regulator? It, of course, helps ensure the fuel pump is receiving the correct signals to shut off.

 

Got it started twice and didn't touch it for a couple hours and now its not starting again. I checked for spark at the plugs and got nothing. I already changed the CAS, Ignition coil, all the spark plugs and wires, and the ignition control module and I'm still not getting any spark. Also the fuel pressure regulator is bad, the pressure in my system would drop and it makes a small hissing noise when ignition is on, but I don't think it would cause a no start.

 

I wonder if the problem isn't related to a change in...wait for it...the weather. I'm probably reaching a bit here but if the temp has increased something may have expanded? I know it sounds silly but I can't help but wonder if a crack or faulty wire isn't being impacted upon. I had a 928 that seemed to prefer cooler temps to hot ones. The bird's nest of fuses and relays were housed underneath the passenger side foot board (unventilated) and the dissimilar metal components along with their dissimilar thermal reactions played havoc with starting.

So a crack in the distributor cap might be exaggerated?
Is the coil wire good? Again, in my 928 the battery ground (braided copper) looked fine at either end but once replaced I found the center totally corroded.
How's the coil? Coil wire? Rotor?
Loose wires? Including engine ground.

From the wisdom of others:

ECU Pin 16 that leads to ignition relay was not grounding so the ignition relay was not closing so coils were not getting any voltage. I took the ignition relay out and jumped the pin 3 and 5 using a small wire and then tried starting the car and it started right away.

I also tried leaving the relay in its place and tried grounding the PIN 16 on ECU harness with ECU unplugged and the relay made clicking sound. So for some reason my ECU is no longer grounding pin 16. If you are troubleshooting keep in mind you should have 12v coming on Pin 16 wire. ECU grounds this wire to close the relay which in turns send the voltage to coils.

 

Found and fixed it, the harness connecting to the CAS on the bottom of the distributor was shorting, changed it and it starts right up.

 

That's great. Now, drive-on!