my 85 nissan pickup with the z engine and carb stops running about 30 seconds after starting. It wont start again until the next day or so then runs fine for a week and does it again. I can get the engine to run for a second with starter fluid but then dies. ???
and carb stops running about 30 seconds Did you meant the car stops …?
My guess is the fuel pump or pickup. The interment stuff makes it difficult to check buy checking pressure and volume output could spot something. You might just replace the filter. How long has it been since you replaced the fuel filter … Yea, I thought so. 
yes, the truck stops running after about 30 secs, then will crank and crank like there is no fuel getting to carb (which there probably isn’t) and it wont start for about 24 hrs, then fires right up. Doesn’t do this between stops, just if it sits overnight, and even then only occasionally. Parking it facing down hill seems to help. Also having trouble actually finding the fuel filter location on the vehicle, though I suspect I’m just looking in the wrong place and will continue to search. The engine will start briefly with starter fluid or remnants of carb cleaner fluid. Pulled plugs and cleaned and dried - didn’t help.
For some reason, my 1990 Toyota w/ carb had a standard mechanical pump on the engine, but had the filter way back near the fuel tank. I don’t know why they did that, but was always a pain to replace. Lying on your back, with gasoline running own your arms. Even when I pinched of the fuel lines with clamps, gasoline always ran down out of the newly disconnected filter.