Where can i get a fuel level sensor for a 1987 nissan 300zx?

TPS, THROTTLE POSITION SENSOR may be bad, loose, etc.,

hard to diagnose whithout seen it, but; have you checked ignition timing.
cam shafts timing- looked at boost gage-if the boost indicator does not
move, check if the booster turbine are not jammed. Also would be good idea to check throttle position sensor output and catalitic converter for free flow.

what are the biggest size rims i can fit on 1987 nissan 300zx without cutting frame?

if fuse and relay good sound like fuel pump going out.

You can get to it thru the trunk, take out upholstry, there r 2 sets of wires going to it. Remove the 2 screws to access the top of tank.

Order one from www.courtesyparts.com (Courtesy Nissan in TX) - they were great for all the years I had my 90 300ZX.

change oil and filter put a emission cleaner in fuel

I would check for a blown fuse there should be one just for the fuel pump. If the fuse is good I would look for a bad or lose wire.

inside the door pillar , behind passenger door . sorry no picture . strange location but thats what the manual says . for 87 nissan 300zx . hope thats a fix ya !

I had the same problem last year mine turned out to be a crank sensor I don't know if that is your problem for sure mine wouldn't send any spark from the coil to the spark plug replaced crank sensor inside distributor and fired right up the dealership called it a cam sensor my book called it a crank sensor either way its in the distributor