1991 volvo 240 starting problems

my volvo had both fuel pumps replaced and the fuel lines cleaned out and i still have this problem........the car will start and run for a day or two then it won't start......it will crank but not start.....if it sits for a day or two, it will start again. if i jump the fuel pumps, they will kick in but there is no arc to fire the motor up.......any solutions would be a great help, i've already spent $1,500 trying to fix this problem and i still have it......HELP ME PLEASE!!!!!!!