My 94 volvo GL die on me on the road. Took it to the mechanic and call me next morning that nothing is wrong. It start right quick. Couples days later will not start. Took it to the dealer for diagnostic replace the speed sensor. Run perfect for a week and same thing happen and won't start.

TRY NEW FUEL FILTER /PLUGS AIR FILTER

Sounds like you need a fuel pump. There is an access panel in the floor of the car to get to the pump.

The battery is dead. I don't know why it dies so quickly. I have the same problem. If my car sits for two days without driving it then it dies. My car was on the side of the road for three days and it wouldn't start. Something is draining the battery.

did you check the battery cables. make sure they are tight.

if you are where its cold you may have a freeze gas line or its time to replace the battery if you are where its cold put some gas line anti-freeze in the gas tank any way and add some more gas to the car wish you the best of luck Michigan Man.

Crank sensor. Next time it does this spray some water on it and see if it cranks. Its by the crankshaft pulley towards front of car.

You have a bad ground connections somewhere.

TRY ANOTHER FUEL PUMP AND FUEL FILTHER THESE PUMPS ARE FUNNY ON VOLVOS HAD SAME PROBLEM ON 850 TURBO AND SURE ENOUGG IT WAS THE PUMP

You need to take a pressure and volume measurement, most fuel pressures for a carburetor engine are 3 to 7 psi, then you need to make sure the volume is consistent for a period of time, 20 to 30 second of engine cranking while the fuel is transferred to a container of some sort, make sure the ignition system is disabled to prevent you from blowing up the property.

I had a similar problem.
At a cold start the rpm would come up normally then slowly drop then stall out. Car would stall at lights and stop signs. My mechanic after having for 3 days found a faulty cam sensor.