I am relatively new to the VW world. We recently purchased a 71 Bug Convertible in pretty good shape. It starts up OK and idles OK----but after a while sputters to a halt and dies. Usually it starts back up and will run for varying lenghts of time- but will die again. I suspect it is a fuel problem (filter, clogged line, pump or ?) When it runs - it runs very strong. What do you folks think the problem and cure are?