Engine not starting

My step-son has a 1991 Dodge Daytona ES with a 3.0 V6 engine. Last week, on a very frigid morning, he stopped for gas and filled the tank. After leaving the gas station, the car started running rough and with only a top speed of about 40 mph. He called me and I told him to stop and get some dry gas and put into the tank, thinking the conditions had caused the tank to have condensation. When he returned home later that day it was still running rough. I started it when I got home and when I tried to leave it idle, it stopped. I tried to restart it, which it refused to do. It almost felt like it had no compression. I first though the timimng belt was bad, so I removed the valve cover and turned the engine over. The valves operate. I could smell gas and now I'm wondering if there is some sort of EFI module that is bad. I have spark at the spark plug but wonder if it's hot enough. I'm thinking, ignition coil, distributor cap, or something with the EFI. What about an injector problem? Could it have picked up dirt, if so why would it not start now? Any help would be appreciated.