[trularin]

Vapor lock is caused by boiling the gas out of the furl system. Morris is correct, except I heard was a littel lower.

Once boiled out, the pump has to deliver gas to a system that is locked by the pressure built by the boiling.

Hence the pump can not deliver gas as it thinks the system is at full pressure.

You can install a bleeder fitting which allows you to monitor the fuel pressure . This would be the first thing to do.

Once you have determined you have this condition, you can install an assortment of things to help with the problem.

Fuel coolers are a favorite solution.
Pressure regulator with return line works as well.

Hope this helps.