Volvo Repair: engine hesitation, engine hesitation, excellerator

Question
Hi, I have an 87 240 wagon with 250,000.  Twice now while climbing steep hills (one at highway speeds, the other excelerating from a stop) the car has "staggered" for just a few seconds then returned to normal.  I had been on a road trip (with rest stop fuel) so I ran some dry gas through.  Thought it helped but it has done it again when coasting, with a light excellerator to maintain speed.  I think the fuel pump pressure regulator is on its way out for the car needs to be cranked twice for warm starts.  There is also a droning hum from the engine compartment that has been there for months.  Any insight you may have would be greatly appreciated.  Thank you

Answer
it could be the regulator or the in tank pump or the main pump.without it happening and being able to check fuel pressure you just can not be sure.the cranking when warm may also be a fuel pump check valve that is bad.this is a valve on the main pump that looks brass in color.