Any suggestions other than wrapping the fuel rail. There must be a better fix than wrapping rail. Never had problem until I redid cooling system last summer, ie. new cooling parts. Help - very frustrating.
I don't know where you live or if they switch to "winter gas" there, but if your winters are fairly mild, try switching to a 160 stat. And I would welcome any comments on the validity of this. It confounds me too.
Try to isolate your fuel rail from the head and intake. I used to have this problem in a bad way. When I used rubber grommets between the rail mount and the intake (don't forget the bolt), the problem completly went away.
Go by your local hardware store, and look in their specialty washer bins. You can probably find some suitable teflon, or nylon or rubber washers. Try to find some with a lip that will keep the bolt from touching your mount.
This really does work. Don't forget to get the part of the rail that goes around the front of the engine. That gets hot, too.
You could also try getting an aftermarket fuel rail. More volume of fuel will decrease the incidence of heat soak. Or you could get one of those ugly ZX fans that hangs over your valve cover.
It can be fixed, but you'll have to figure out how you want to do it.
Changing your thermostat will not help you. The problem isn't caused by the temperature of the car while it's running. It's caused by the temperature of the car after you shut it off. The temp goes way above normal after shutdown, since no water is flowing or being cooled. Even if you had an electric fan on your radiator that runs after shutdown, it wouldn't help. The water that needs to be cooled is in the block. Read reply to original poster for ways to cure this ill.
Heat soak and Vapor lock can evidence themselves in seveeral ways, each from a different heat source.
If the problem is a motor running too hot, and fuel boiling in the fuel pump, then an electric fuel pump to help move fuel through the rail and pump quicker helps considerable if you enlarge the return orifice to take advantage of it.
Wrapping the fuel rails helps even if you don't wnat to hear that, as well as wrapping the fuel lines to the CARBS and FROM the hard lines on the chassis rails. Isolating the metal hold-down brackets from the head with phenolic also helps with thermal transfer from the head to the fuel rail.
A cooler thermostat should help some, but if you don't have a heat-shield over the exhaust manifold, radiant heat is going to boil the fuel in the float bowls in heavy usage or stop-n-go.
Winter/Summer gas is a VERY good observation, especially at this time, our temperature out here yesterday was in the low 80's, yet we MUST be using the winter gas from oct to may, soooo.
Timing can have an affect on how hot the car runs, too much advance, and you heat the head, run retarded enough, and you have a glowing red exhaust manifold. So goes it with AIR injection, if it's pumping when it's not supposed to, you can really heat up the exhaust.
Headers? Well, you put 'em on--now you pay the price (o get maybe 2HP over 6500rpm...)
And last but not least, you can install a major-sized cool can made out of a 1 gasllon Igloo beverage cooler and some copper tubing. It will hold 7# of ice, and last about 1 hour driving at very high speeds, in very high desert temperatures before the ice turns to 120 degree water!
And this is with SU's right? If it's triples, the same things hold true, but there are a few more things you can do, depending on the brand...
Checked the archives yet?
I used to have this problem with the stock engine and carbs. The metal fuel rails conduct more heat into the gas than rubber hose so I eleminated metal wherever possible. I ran a long hose from the fuel pump on the passenger side foreward around the front of the radiator where the air is cool and back to the carbs using a brass "T" at the front carb. I cut off the last inch of the fuel rail where the orfice for the return was and plumbed it in to maintain stock fuel pressure. It only got into the 90's where I lived but the problem went away. Total cost around $10 for fuel hose and a couple of fittings. Good luck!
Since you have fuel injection in the 77 (I had to search your old posts for this info) the problem could be electrical but still related to the heat in the engine compartment. Search for other mimics, but my problem was the fuel pump relay. Get it checked first ($81). Isolating/upgrading the fuel rail is probably good for other reasons, but I don't believe the fuel boils in the higher pressure FI systems. I isolated all the contact points but there is still a hot water line integral to the rail, running for the water temp. sensor. It seems like most the heat is coming from there. I still starved for gas and became an obstacle on a blind corner.
Engineers at Nissan worked on this after field problems at their dealerships complained. Many field fixes were tried.
Nissan designed in "cures". One was the vents in the hoods. That didn't work as well as they hoped, so they went to a fan that blows air on to the fuel rail when the temperature reaches something over 230 degrees (don't quote that, the number is higher than your car will get if it is running). They powered this fan so that it could run with the key off. What do you think that tells you?
Most people don't have intermittent FI relays. They usually work, or they don't. More likely it is a fuel/heat issue than the electrical one you propose. I hope that he spends the $2.00 on the washers I recommended before he plunks down $81.00 for your relay.
I am not going to back read for the original post, but if your car has the early system that requires the AFM Flap to move to turn on your fuel pump, then that's half your problem. The fuel in the rail boils out, and the fuel rail must be bled afterwards. This is why the Fuel pump runs in the "Start" position--overridden from the AFM contacts.
What you want is a way to start the fuel pump to bleed the fuel rail BEFORE you crank the car---like the 82/83 models did, i.e. turning the fuel pump on in the "On" key position for five seconds.
The easiest fix that I've found (and I've rigged temporarily to my 76) has been to put in a toggle switch to open the circuit to the solenoid from the key. This way, the fuel pump runs in the "start" position, but you aren't there cranking the **** out of hte car waiting for the bubbles to bleed out and for the injectors to get enough fuel to fire off the car and start it.