won't start

It seems when the roads are wet, snow melting, when I turn off engine and get back in, it won't start....usually have to wait at least a half hour before it will start....what would be getting wet?

I have a 1999 Ford Expedition....It seems when the roads are wet, (snow melting), when I turn off engine and get back in, it won't start....usually have to wait at least a half hour before it will start....what would be getting wet under neath????

A few questions. Is it cranking over and won't start or is it not able to crank? If it isn't cranking, is it making a clanking/puttering noise? If it does crank, when you turn the key to the on position and before you move it to the start to begin the crank, do you hear the fuel pump start up to pressurize the fuel system? Doesn't matter yet, but which engine does it have?