My 1972 BMW 2002 single-barrel has a vapor lock problem after it has been sitting for a short time after being run on a hot day or after highway driving on even a warm day. The replacement fuel pump puts out 3 psi (not to specs, I know), all hoses and connections have been checked, and the hoses have been rerouted away from heat sources.
Author: Gary Sullivan
As you note, your pump is not putting out the required 3-1/2 psi. Vapor lock is something that a 1972 2002 seldom experiences. The most likely cause is a pinhole leak somewhere in the lines or a loose connection. Tech Ed.