Does the pump still run when it shuts off?
With that being said, I have experienced a similar issue with a Celica. It turned out to be the ignitor not giving a feedback signal to the ECU. Have you checked for error codes?
Check out this link on how to do so if you haven't:
http://forum.ih8mud.com/threads/how-or-where-to-read-codes-for-a-1994-80-series.470427/
It's US based, however things should be very similar/the same.