1990 pltymouth voyageur

We have a problem with our 1990 plymouth voyageur. Recently the temperature went to -5 degrees celcius. I went out to start the van and it just turned over with no luck. Lasy year we had the same problem even when it was plugged in it wouldnt start. When we did manage to get it start it took many times to crank it over before it would start. We had it put on a computer scanner and no ones knows why it wont start in cold weather. The one thing I notice while trying to start it is not hearing the thumping noise when it gets fuel. We had the temperature sensor on the manifold changed because we were getting code 355 so it was changed. So we are trying to figure out whats going on. Is the gasoline freezing or moisture in the gas system