Volvo: Stalling Problem on 1993 850, fuel pressure gauge, wheel sensors

Question
I have a 1993 850 that started to have a stalling problem a couple of months ago.  Recently it has become a real problem as I never know when it will work or stall out. It usually stalls after I have been running it  for a couple of minutes and very often on damp and or rainy days.  It usually does this as I am driving down the busy street.  I have had it in to see a mechanic and after some diagnostics there seems to be no spark, and we have replaced the Cam Sensor, Fly Wheel Sensor, tried a new Coil and Amplifier and even try a different ECU unit.  When we replaced the Cam and Fly Wheel sensors it seemed to work for about 4-5 days but once again the same problem has occured and it is back to the shop.  HELP !!!

Answer
William,
You mention damp or rainy days, did you inspect the cap rotor and wires? Do you feel the engine missing before it dies out? You may want to replace the fuel pump relay as a precaution, they have been know to go bad. You could install a test fuel pressure gauge and see if you lose fuel pressure when the car stalls. There will not be any codes set if the fuel pump or the relay where bad, they are not part of the cars diagnostics.