Volvo Repair: Volvo 240 with starting problems, electronic fuel injection, fuel pressure regulator

Question
Regis,  I have a 1989 Volvo 240 that has had episodic starting problems for the past year or so.  Sometimes the battery will be low/dead or the engine will rotate but not start.  The battery was replaced a few months ago but it continued to go dead on occasion.  I've made sure all lights are off; under hood, inside car and trunk.  But it went dead again last month and didn't have time to deal with it.  I just recharged the battery, checked all fuses, put in some gas (just to be safe) then went to check it out.  There's a hissing noise coming from the fuel pressure regulator area.  I dropped soapy water on all hoses, around the injectors and all over the regulator but couldn't detect any leaks.  I also hear the gas tank fuel pump running, I think, both from inside the car and through the gas fill tube.  The hissing and pump are running without the key in the ignition!  It stops when I pull the engine control fuse, under the hood.  I put the engine control fuse back in and the car just started.  When turned off the same hissing and pump noise is still there.  So I assume the running pump was causing the battery to go dead.  But why does the gas tank fuel pump keep running and what do think the hissing is about?  This car has the LH-Jetronic electronic fuel injection system, if that's important. My Haynes repair manual says there's different types.  Thanks for the help!  

Answer
the fuel pump relay may be sticking closed.this is located behind the felt panel above the passenger leg area.without hearing it I am not sure what the hissing noise is.I woud try disconnectign the fuel pump relay and see if that stops the pump noise.