hello my name is Luis, I being working on this 280zx non turbo, did head gasket replacement, sent head to machine shop to have it serviced, installed head back the with new gaskets, tune-up parts, including fuel filter
coolant switch for ecm, t was hard to start, I found out that the injectors had very low voltage while cranking, checked all power and grounds, they where ok, some how, when I was checking I disconnected head temp sensor and forgat to reconnected back, so when I tryed to restart again,it did start !! ran fine in the shop, set ign timing, and took it to test drive, I could not go more than 40 mph no power !! rechecked again oh but have to say, if reconnect head temp sensor will not start so drove with it disconnected. rechecked and found out did not have signal for temp sensor and cold start valve, I replaced ecm and after that I'm able to reconnect head temp sensor and have it running, now after drive it half a mile looses power, check fuel press within specs. I still have no signal to the cold start valve, and no power after warm. any ideas ???

A bad or disconnected CTS or O2 sensor both cause a rich condition. This makes for hard or impossible warm restarts and can run so rich it fuel fowls the spark plugs.The fact that it starts with it unplugged indicates you aren't getting the fuel you should be getting, a dead spot in a AMF can cause some weird issues and is what I'd suggest you look at. I have seen a few of these cars where the fuel pump fails intermittently, the pump is external and gets hot and shuts down, something to keep an eye out for.