I am not familiar with L-Jetronic fuel systems but you should check all your fuses. My 1974 (Spica) Spider had a clogged rear fuel filter that showed similar symptoms. With the fuel line to the Spica off, the fuel pump would fill a peanut 'catch can' in a few seconds but the car would stall after running a while and not restart until the next day. I finally got a gallon jug to use as a catch pan. After pumping about a quart of fuel the flow just stopped -due to a clogged fuel filter.
Here are some L-Jet links to get you started: