OK 72 240z. Runs excellent, like new except for one thing. When Im in stop and go traffic and shes a bit warm (not hot) I start getting fuel delivery problems. Its like getting air in the fuel line. Im running just a mechanical fuel pump. Ive looked under the hood out of curiosity to see what is going on and the fuel filter is sucking big gulps of air along with my fuel...even on a full tank of premium.

Question: Why is it happening only when the car gets warm?? Where is the air coming from?? How can I fix it??

...Ive tried 2 different fuel pumps, no change. Is this vapor lock?? Why at the fuel filter???

Check to make certain all of your fuel hose clamps are tight. Both at the filter and also at the tank. If they are loose it can suck air there.

why only when its running warm on a hot day? if it were a loose hose clamp wouldnt it do it all the time? ......but i will check them all tomorrow////

are you sure it's not getting too hot? are you running the water intake for the carbs. I have learned not to trust the factory temp gauge...

I am running the water to the carbs, yes. Is that bad?

I dont think its running hot. Hmmmmm......

guess I could drive it then shoot the radiator with my laser thermometer????

depends on your definition of hot.. we have not had a hot day here yet.. and if your gauge tells you wrong information, and your coolant is really VERY hot, that could assist in vapor lock.. just a thought..