IT MAY NOT BE A VAPORLOCK>>>>>>>.
I'm having a problem with my '76 280-Z ,when the weather is hot .I can
drive it 2 to 10 miles and then it quits and won't start again for
It's like it's getting to much gas ,but the fuel pressure is only 32 to
42 psi . I
have a new pressure regulator and my engine vacuum is fine .My engine
temperature is fine and running about 180 deg.
As per a tip I received, today I 've had the time to sit in the car and
for any length of time @ 2500 rpm ,my fuel pressure guage read about 30
psi and I had about 18 psi of manifold vacuum.
It ran for an hour @ 2500 mph "i was about to give it up" when it started
to misfire .The rpm dropped to 1500 ,the manifold vacuum dropped to
14 psi and the fuel gauge was showing "0" .It ran for an other 3 to 4
getting progressively worse and the gauges getting lower & lower ,until
it stalled all together.I think that the tach followed the engine slowly
Your problem is more than likely a low fuel pressure problem. Perhaps the fuel pump or regulator is getting some age on it. Anyway, if she cranks and runs good, don't sweat it. Here is what I did on my carbureted 71 240Z. I put five wooden clothespins on the fuel line and fuel rail. This really works. My friends dad did it to a tractor and told me to do it. What you really need to do is insulate the fuel line by wrapping it in an insulation. When I was in heavy traffic, I would pull the hood release and the hood pops up to the catch and this allows air to get out and afterall, the hood hinges at the front and will not blow up on you like most cars would do if the second catch failed.
If you do not have a factory service manual, GET ONE! You can order one from www.ideal-z.com. Their page will have a link to Courtsey Nissan, who will have the manuals. While at the Courtsey Nissan site, order the Ztherapy FI video. It too is a must have along with the FSM.
The info you need is in the engine fuel section... pay close attention to the air flow meter tests, water temp sensor tests. Other things to check in the engine electrical section is the ignition transistor unit and distributor and coil.
Be sure all the FI sensor connectors are clean! (not on the outside, but the contacts).
The FI Z's rarely have vapor lock. Most of the problems with stalling is crud in the tank/lines, bad FI sensors and wiring, bad transisitor unit or distributor.
I agree with JohnB that vapor lock is not really a problem in FI Z cars BUT they do experience "fuel percolation". This happens when an FI car is idling for extended periods in hot weather and also when you drive the car to Wal-Mart, spend 15-20 minutes in the store and then come back out to drive off. During that 15-20 minutes, you will find that the cars can often sputter and act like they don't want to run but after a few minutes the "percolated" fuel is flushed out, the fan starts doing its job and all is well. Percolation is somewhat, AFAIK, a precursor to vapor lock. I have owned 3 different FI Z cars over the last 12 years and have never had vapor lock problems; only the hot start percolation. The problem has never stranded me or caused my car not to start but it does cause worries
78SilverZ, give us a little more detail about what the car is doing and when it does it, the conditions that the problem occurs in, etc. That will help. The problem could be anything but details might help us narrow it down.