my car wont star

what motor?

you can try water proofing all ignition parts with wiredry or silicone spray or similar products.

replace the dist cap and rotor with a GOOD quality part not a chinese made one. Standard is a good brand name to use forelectrical. tis code may be setting if the truck runs crappy on the rainy days. also if your plug wires are as old as the truck then you might think of replacing them.

I have done all of that, and it doesnt work. It only works on dry days

The engine is a 5.7

you could have a short in the ignition circuit which a pro would have to find as he would be more familiar with it and where to go as that is what your code is .