I recently acquired a 1984 300zx non turbo in non running condition. I was told it had run well recently, After getting it home I found a fuel line leak on the tank side of the filter. After cutting off some hose and clamping the hose on fuel leak was solved and car ran well for a few days of moving it around in the driveway but was not test driven due to no tag. Once tag was obtained and ready for test drive the car will not start unless fuel is supplied into air intake then it starts instantly.

Fuel pressure check shows 55 on the engine side of the filter. Unfamiliar with the noise the fuel makes going through the regulator I thought the diaphragm was leaking and needlessly replaced the FPR. The fuel pump runs while the key is on, it never primes then stops as it did when the car was running. I have downloaded the FSM and gone through the ECU diagnostics and get codes 23 and 31 as expected but nothing else.

I have checked ground connections and all electrical plugs for connection. Everything seems in order other than the fuel pump runs continuously with key on but engine gets no fuel. What is the next diagnostic step?

Please help - thanks

Check your tps connection (code 23), really check all the connectors, the mas and chts would be the most likely suspects. That's the thing about 30 odd year old cars, the electronic connectors can be a bit troublesome.

I had some time to get back to it today.
air flow meter:
has voltage. I couldn't check continuity as my meter doesn't have that setting will have to get a better one. Checking terminal c and f it has resistance .
Throttle valve switch:
checked 18 and 25 and got 0 resistance.
Injector:
Checked eccs 15 pin connector, 102 and 105 have voltage. 101, 103, 104, and 106 have no voltage. The next step for this check is to check continuity at each injector which i didn't do until i get a better meter.

Also, added new battery. Cleaned terminals. Disconnected body ground, sanded, reconnected.

I cant imagine that the injectors are the problem. It was running fine. Has to be something loose or not connected someplace.

If any sees something obvious in what i have done so far please advise. Otherwise i will get a new meter and go through these tests again.

Thanks

Could be a bad ecu. When you have odd symptoms that don't make sense it's often the ecu. the fact that the pump doesn't just prime and stop with key is odd but could be a sticking fuel pump relay. The fact that you have fuel pressure and no fuel being delivered could be a bad injector relay, or lack of power to said relay (which you need to check), or a bad ecu (could also be one of the power or ground circuits to the ecu). with this combination I'd strongly suspect the ecu, could also be an issue in the harness.

The problem preventing starting was the power transistor, sometimes also called ignition module. Once replaced the car starts and produces code 44 indicating all is well. When cold the car drives great, but after a few minutes the engine "bogs" at low throttle but will clear if given full throttle. I still hear the fuel pump running continuously - it doesn't prime and stop running when the key is on and engine not running. I think maybe its getting too much fuel to run well at low throttle but am puzzled by why it runs smooth when cold. Also, since the error codes are gone now, I don't know what to check. Any ideas? thanks

So to recap the issue was not lack of fuel it was a lack of spark, glad you got that resolved.

You can measure fuel pressure using an inline gauge but I doubt that's the issue here. Generally a rich condition doesn't clean up with more throttle, it gets worse. I'd start by calibrating the TPS, clean and check the connections at the TPS as well as the MAS, Might also be a good idea to check the ignition timing. Once the housekeeping items are handled, how well does the engine start after being warmed up? good cold start troublesome warm starts are usually the CHTS, Fuel temp sensor or the O2 sensor, and in many cases it's just a bad connection.

unplugged the 02 sensor and cleared the issue - thanks for all your help