I have a 1990 300ZX NA 5-Speed. Bought the car (non-running) for $600. The guy before said it had some sort of electrical problem and when you turn the key all it would do is click, I think he might have been lying to me. I threw a battery in there and the first time it turned over but wouldn't start. We dumped out all of the old fuel and put in fresh, still no luck.

We noticed that when we turn the key the fuel pump does not start to pressurize the system. We take off the fuel pump relay and jump the wires and the fuel pump works great, but it stays on all the time. Tried starting the car like this but that didnt work either. We are getting power into the relay but not after that into the fuel pump control unit. We get power to the control unit if we jump the fuel pump relay but not otherwise.

When I turn the key on there is no check engine light. Also, the LED for self-diagnostic in the ECU does not turn on at all. We tried completely unplugging the ECU and when we start it the exact same thing happens. It's as though the computer is never plugged in.

We are getting spark and air but no fuel. We spray starting fluid directly into the intake and it tries to start until all the starting fluid burns up.

Fuel is pumping fine up into the fuel rail and out of it as well but the computer is not telling the injectors to spray. Fuel pressure seems fine too. I read another forum on some site about a guy with a similar problem. Turned out to just be a ground that wasn't connected (he said that the engine ground that connects to the rear drivers side of the head is the groud for the injectors and fuel pump). I am at work right now so first thing when I get home I will check that out.

I would really rather not buy a new computer and then that not work. I took it apart and it doesn't look fried up or anything, I saw some pictures of some that got fried up and mine looks brand new compared to those.

Anyone have any ideas other than grounds or the ECU? Another small problem is that the headlights never turn off unless I remove the relays. Key off, key on, key in my pocket, it doesn't matter, they don't turn off unless the relay is taken out or the battery disconnected.

A couple other things, looks like the PTU has already been replaced with the newer one. I've already replaced the fuel pump relay and headlight relays. We did different voltmeter readings in different places with the key on and off; we found that the injectors are getting power all the time, even when the key is off/out, is this normal? The previous owner claimed that an aftermarket stereo was being installed and then it wouldn't start. He replaced the power steering contol unit as it was competely fried (looks obviously fried, I took apart the ECU and fuel pump control unit and hoped that one of those would look fried up but didn't).

Could a bad ground cause the computer not to work? Let me know if you need anymore information concerning this or if you have any ideas. Thank you so much in advance for your help. This is my first Z and I can't wait to get it running.