1976 280Z with 104,000 miles: Clock stopped many months ago, volt gauge always on the high side with no change, fuel gauge varies from 0 to 1/2+ even when filled up for many months, Temp gauge varies from 0 to hot side during extended freeway driving (past few months), oil gauge just started erratic behavior one day ago.... registering from 0 to about 1/4, though oil level is at High mark (car serviced a few weeks back). All fuses in passenger-side box check out OK. Sometimes after extended drive & 15 to 30 min shutdown (engine still hot), car will not start up & fire without several attempts at starting.... followed by a rough start.
Any assistance will be greatly appreciated at trouble shooting the problem (s)
Unfortunately my service information only goes back to 1980. But let me give you some basics on each issue:
1 - To check the fuel gauge only going half way up you need to ground the wire leading to the sending unit in the fuel tank, with the ignition on. If the gauge goes all the way to full, the sender (or ground to the sender) is no good. If the gauge still only goes half way, it's a bad gauge or high resistance in the circuit from the sender to the gauge, power feed or ground.
2 - Check the actual coolant temperature at the radiator with a thermometer. If it agrees with the gauge the coolant system is in need of service (flushing the radiator, block, check coolant fan operation, air flow path through the radiator, etc). If the thermometer does not agree with the gauge, the gauge/sender circuits need to be checked similar to the fuel gauge problem.
3 - Oil pressure, same thing. Need to hook up an oil pressure gauge to see who is right. Oil level full does not mean you have good pressure.
4 - Hard start and running rough on a car this old can be a bunch of things. But start with the basics and check for fuel and spark when it won't start. Don't think I can remember that far back, but if it is carbureted, that may be the issue. The ethanol in today's gasoline is a nightmare for internal carburetor corrosion.
Hope that helps.