Volkswagen Repair: 78 beetle convt. electric fuel pump, electric fuel pump, seat belt sign

Question
When ignition is turned on the fuel pump doesn't always turn on.  I have run a separate ground to battery from pump, checked fuses.  The car can run fine for 15-20 min. at that point the radio will intermittently turn off the fasten seat belt sign will come on, and sometimes the fuel pump will shut off.  The car sat uncovered in Calif. for 2 years prior to me buying it.  I have connected a 12 volt source to the pump and it operates fine.  What should I try next?

Answer
John,
The fuel pump only runs when the starter is cranking. The microswitch is in the airbox, operated by the engine vacuum pulling the "barndoor" open enough to work the switch. There's a disc on this door that sometimes pops off if the motor backfires through the intake. Pull the big intake elbow off and check it out. You'll probably need to remove the air cleaner box as well. They have the pump set up like this in case the car's in an accident....the fuel pump won't keep running, possibly feeding a fire. The double relay behind the backrest of the rear seat could be the problem as well. There's quite a few things that could be going on here. I'd recommend picking up a factory VW manual, by Bentley. You'll need the Orange book, covering '70 to '79. There's an excellent section on fuel injection towards the end of the manual. I hope this helps!