My '78 280Z feels like it's 'vapor locking' after is sits for about 15 min, once it's been run and the engine is hot. The fuel rail heats up and you can't even put your fingers on it. If you continue to turn it over and get cooler fuel into the rail, it will start and run just fine. Someone told me that it could be the newer fuel (CA) that is causing the problem. I've replaced the fuel filter, fuel regulator, plugs, repaired the AAV, checked out the Flowmeter and I'm stumped! Thanks in advance.....

Welcome!

I've moved your topic to the DATSUN Z area. The people here will be better able to assist you with your vehicle.

Vaporlock is a known problem. Some people wrap fuel rail in aluminum covered insulation to prevent heat intrusion. I know of no perfect solution.

Vapor lock was more of an issue wiht the carb'd cars, the fuel injected cars by their very nature are less of an issue. Certainly wouldn't hurt to wrap your fuel rail in heat reflective tape or insulation. Just cycling the key on the fuel pump should come on and start pushing fresh fuel, you might want to just cycle the key and wait for the pump to stop then cycle off the key off then try to start. Your issue could also be a bad fuel pressure regulator, a fouling fpr will allow the fuel to drain back out of the fuel lines when the car is shut off, meaning you have to prime the system again before it will start. A more common issue is the CHTS or theO2, when they go bad it causes a rich condition making warm restarts difficult.

Thanks for the comments.... it is frustrating with the fuel injection. I'm not familiar with the CHTS.... is it the same as the temperature sensor that is by the thermostat housing? I replaced that one on Friday and took the car for a run and it still had the problem.

The CHTS or CTS on you can should be located in the lower thermostat housing, it's the one wiht a 2 wire connection that looks like an injector plug.

Assuming the CTS and O2 are good, we are back to the FPR, is the system holding pressure? or is it all bellding off?

Injector heat soak is an issue that Nissan knew about, and took steps in the 79-83 ZX to mitigate with the injector cooler fan. Even if the cylinder head temperature sensor, and the oxygen sensor are in good shape, the fuel pressure regulator is good, and the fuel pump and filter are in good shape also, the fact remains that the exhaust manifold sits below the intake on the L28E engine. After you shut the car down, paradoxically, the block and exhaust manifold will actually get hotter than they were while running; The reason is that water is no longer flowing, and the exhaust gasses are no longer helping to carry heat away. During this 'heat soak' period, the heat will rise from the exhaust manifold, and conduct out of the head, and into the intake manifold. The result is the injectors and fuel rail get hot, and since our fuel system is a return fuel system, as fuel pressure in the rail drops during heat soak, the fuel gets room to vaporize in the rail and cause hot hard starting issues.

The 280ZX minimized this by using hood vents, and the injector cooler. A lot of ZX guys rip the injector cooling fan off and claim they "don't need it". But as djwarner said, vapor lock is a known issue; So is its related issue,injector heat soak. The best ways I can think of to help mitigate this, if all the other equipment is in good shape, is to make sure the intake manifold is clean, free of a layer of grease and grime which can insulate it, make sure the fuel rail is also not caked with anything. A possible option available to you is also to put an injector cooler fan from a ZX on it; They're around, on ebay, because ZX guys always looking to clean up the engine bay toss them out. On the ZX it's connected to a timer that's connected to the cylinder head temp switch, in a 280Z, it could be wired to a switch.

Before resorting to throwing a cooler fan at it though, do make sure the thermostat, cylinder head temp sensor, and O2 sensor are in good shape, and the engine is timed according to spec, as all these systems work together to keep combustion chamber temperatures, and thus engine temps, low.