So my truck has done this three times now. First time in San Francisco when it was really foggy (not unusual). Replaced distributor cap (due to a completely different problem) the next day while it was clear and sunny. Still would not start. Let it sit another few hours. Started up. The next day drove the 150 miles home. The second time (within a few days of this) started pouring, had trouble starting it but it eventually did. Drove all day in the pouring rain with no problems whatsoever. Long story short it rained for another two days. Cranked that whole time while raining...nothing. the weather cleared up and Since then the truck has run just fine without a hiccup. Any ideas?

 

This may or may not help but I experienced similar problems recently. I bought a 1996 Tahoe with the problem as the seller sated, "sometimes vehicle will not start on damp rainy days." The previous owner stated the dist cap had been replaced. The vehicle also stored a 1345 code. I changed the crank and cam sensors to no avail. Mean while in the process between starting and not starting I replaced the cap and rotor as a set and the engine has never failed to start every since. I adjusted the distributor and eliminated the 1345 code and the Tahoe now runs great with no problems.

 

I've had a sneaking suspicion it has something to do with the distributor. We did start the truck at night and I saw an orange flash from below the distributor cap. Maybe a coil problem too? Definatly going to replace the rotor and plug wires. Hopefully that's it.