Can't say for certain, but seems logical your fuel pump should always cycle on and stay on. Dirt water or whatever in the filter will affect performance but not shut the pump down. Relay is the wild card. Just don't know.
Sounds like a defective pump, and if you do a search on the threads here some others of greater detective skills than I possess have found alternatives to the amost impossible to find replacement fuel pump. (I saw an 851 sit in a shop for a year waiting for the factory replacement).

Sorry to spread my comments on multiple posts, but I did have an experience where my fuel pump would not come on at all. Assumed it was the pump, but after opening up the computer under the seat I noticed the circuit board had a short in it. (water intrusion--tiny burned place that is possibly repairable) By dumb luck the shop guy helping me happened to have a used one he sold me for $200. 10,000miles later all is well.

Hi,
the 907 fuel pump is a Bosch, part number: 0 580 463 999.
No matter, as Chrisjpitt told, every submersible 12v pump will work.
Ciao

thanks to all who replied !
chris had it right. it turned out to be a intermittant relay in the front left panel. i pulled the one controlling the fuel pump and cleaned up the internal and external contacts, problem solved, has not happened since. i carry a spare now.