89 240 Wagon starts up fine then i drive to the gas station or deli (few miles) and the car will not start up again. i wait 5-7 minutes and it starts.

took it to the local reliable volvo mechanic who said the timing sensor in the flywheel housing was coated with oil from a bad rear main seal. so they replaced the seals and it drove fine.

now a month later, i go to the gas station and again it wont start up, wait a few minutes and it starts.

2 days later, just left the house driving down the road at 50 mph (approx 2 miles) and the engine shuts off. pull over and the car restarts right away, but the check engine light stays on. drive back home. later in the day, car starts fine, drive it 150 miles in 3 hours with no problem.

i bring it back to the mechanic and he replaces the fuel pump relay and asks that i drive it for the week to see.

our mechanic is extremely reliable, but i'm curious if other 240 owners have had this problem and what could be causing it. thanks.