I recently encountered a problem that involved.

I recently encountered a problem that involved my vehicle cutting off. I thought it was the fuel pump. I had it replaced by a mechanic who has done other small repairs for me over the past year. However, one day after the new pump was installed the car continued to konk out. After a weekend of visiting family the car repeated to do so approx 7 more times on a 35 mile trip. After a brief pause it usually started again. I looked under the hood to see if anything looked amiss. My power steering pulley looks wonkey, but the mechanic I spoke to said this wouldn't cause the engine to cut out. What could it be?