Chevrolet Repair: roll over but wont start, chevy silverado, heat lamps

Question
its a 1997 Chevy Silverado, 5.7 liter. when it is damp outside, the truck rolls over but won't start. we changed the distributor cap and rotor but it still won't start. the only way we finally got it to start was to bring it in the garage and put heat lamps under the hood. there totally has to be a different way to start the truck besides tucking it in the garage every night with its own heating blanket! PLEASE help and a real BIG thanks from my way.

Answer
Hey,

 Pull the distributor coil wire off of teh coil and look very closely at the tower for carbon tracks down the side.  If you crank it over in the dark sometimes you can see when the spark 'leaks' out of the coil.  Dampness causes the spark to travel wherever it wants.  Spark will rather travel over water or carbon than the air gap of a plug.

Wayne