Our 1996 Caravan had a new transmision put in at around 150000 miles, 3 months later, put on a fuel pump, first 25 miles after that, it stalled at an intersection and would not start...let sit for 8 hours, started fine, stalled after 25 more miles and would not start... this is consistant....starts and runs for 1/2 hour, and won't run until cooled down. Replaced coolant temperature semsor...no change. What might be the problem?