My 91 non-turbo 740 sedan is a regina system with only one pump in the tank. I had an intermittent problem also and it turned out to be a poor contact of the pink(+Ve) wire in the harness located in the trunk. I dont know where yours would be in the wagon. I found out by checking the voltage before the connector while cranking (should have batt voltage) and checking the voltage on the wire (pump side)after the connector. I did get voltage before the connector but not after. Also you may want to check the terminal under the fuse box ,fuse 11 ( at least in my case)to be sure its nice and tight and not corroded. I have had my 740 for twelve years and done two pump changes. Both times there weren't any symptoms of a failing pump. They just quit.