A couple of weeks ago it rained really hard and my car would not start. The next day when it was dry it worked with no problems. This morning I go out after a heavy rain and again no start. I know that it is probably condensation or some form of moisture that is causing the problem. When this happens the engine cranks, but the fuel pump does not come on. Is the problem most likely in the fuel pump or main relay? How do I check to see what is getting wet? Could there be any other culprits?

 

 

Yes, this ^^ is a roundabout way of asking: What vehicle you are working on?

The more information you can give us, the better we can help you.

[The 85 Supra with a Chevy v8 and 35’s would be a pretty crazy car ]

 

I'd Wheel It.

 

Pop the passenger side kick panel off and check for moisture. I've seen a few windshields leak around the bottom and pour into the kick panel and ruin a circuit opening relays.

 

Yes, above are related and quite possible cause of cranking but no combustion because fuel pump does not come on.
Kilocal,
When you crank, do you here theC.O.R. click behind the glove compartment?

 

On a 89 22re pickup that I very rarely drove the rain did the same thing. I tried to crank it one day after a rain to move it and it was just turning away. It cranked right up the next day and all next week . It did not crank after the next storm. I took the distributor cap off to check for condensation, but it was clear. I then grabbed the spark plug wires to give 'em a tug and one of them came right apart. Condensation was getting in my junk wires. Replaced the spark plug wires and never had a problem since.