Heat problem, vapor lock ???

[gmr714]

I have a 74 260z. it runs great but sometimes when I shut it off I have a hard time getting it restarted (For instance when I get gas) it might start but it runs really weak, sometimes it wont start at all for 15 minutes then it runs fine. Is it vapor locked? any suggestions?? Thanks, Mark

[z74z90]

Well, it certainly could be vapor lock. Sounds like it anyway. I am the original owner of a '74 260Z that has suffered vapor lock for its entire life. First make sure the fuel filters are clean...both the external filter in the rear and the filter inside the electric fuel pump. My car is very sensitive to dirty filters.I am running round top carbs from a '72 ,still have the original heavy asbestos wrap on the fuel lines, keep fresh filters and I still have issues. About three years ago I put an injector cooler fan from the 280ZX on my car and run it when the weather is warm. This does seem to help a great deal but it still struggles when it is hot. Good luck.

[gmr714]

Thanks for the info. I changed the electric fuel pump, strainer filter, fuel lines and added an inline filter before the mechanical pump over the winter before I had the carbs tuned. I 'll try wrapping the lines and shielding them from the heat. thanks

[d240zx2]

You could also re-route the fuel lines.

Because of the placement of the OEM fuel pump at the front of the engine, fuel must travel from the pump, down the fuel rail alongside a hot valve cover over a hotter head/intake/exhaust manifold to get to the carbs.

I've rerouted my fuel lines to the firewall, across the back of the engine to a fuel block on the left inner fender. From there, individual lines feed individual carbs.

BTW, I blocked off the return lines to maintain higher in-line fuel pressure. Never have I had a vapor lock problem.

Frank