I had a no start in rain problem on my 98 blazer that drove me nuts. If it sat after a rainstorm or over wet ground, it would not start the next day. Doing some research and testing I was led down the bad cap, bad rotor, plugged distributor vents road. After 2 different caps, rotors and even going as far as drilling a vent in the distributor, it still would not start after a rain. What was odd in the trial and error process was that after leaving a hair dryer pointed at the distributor for about a half an hour it would start to kick to life and soon start. After being very frustrated for months, one day i started systematically spraying down small areas under the hood and found the culprit was somewhere around the distributor. There are a few grounds in that area and had cleaned them to no avail.It took some time after spraying (30 minutes or so) for it to not start, so I assume the water is getting in a harness and on the move. Finding the area, i took electrical parts cleaner and sprayed about three cans down around this area to clean off the oil and grease. Then i sprayed down a few coats of ignition sealer and followed up with a few coats of rubberized undercoat. That was about 9 months ago and it has not done it since. It might not be the end all fix, but i figured id post it anyway and hopefully save some frustration for someone

 

I had a no-start problem with my 95 Blazer as well. It rained pretty hard over a couple of days here and my truck was parked on a bit of an incline. I think I was unfortunate enough to get just the right angle where water made its way onto the distributor. Needless to say, I went out to start it the next day and it would crank but there was no spark and it wouldn't start. It took a long time and a lot of fiddling to get it to run without changing the distributor but I really did not want to do that if I could possibly avoid it.

I used what I had on hand which was wd-40 and carefully sprayed around the boots, wires, cap and coil hoping to displace some of the water. I also used a hairdryer and tried to dry out the distributor area for around 15 minutes before I tried to start it. This didn't really work that well, since it was still wet enough that it wouldn't catch. Since I recently moved to a new town, I didn't have any tools on hand but wanted to try to get some quick start into the throttle body. Without taking things apart it was pretty straightforward (and easy) to disconnect the little hose that attaches to the PCV valve. I worked it free and pulled it up so that it was on a downwards slope to the throttle body and intake. I gave it a little spray of Quick Start and put it back together as fast as possible before I jumped into the truck to crank it for about 10 seconds. As it turns out it wasn't quite enough so I repeated this again and gave it about a 5-6 second burst of Quick Start into the hose the next time. The second time when I cranked it, the truck began to sputter so I floored the accelator which gave it enough that it roared back to life. I promptly took the truck for a half hour drive to get it nice and hot and haven't had a problem since - its like it never happened. So it is possible to get it running without replacing the distributor or trying to get the cap off and spraying carb cleaner inside.

One thing I would say though is that Quick Start and products like it are very flammable and should be used with care. If you do what I did, cover the ignition coil and the area you're working in with a rag or something so you don't drip this stuff onto something which could catch fire. Also, try a little bit at first then just gradually increase the amount until you can get it running. I'm going to follow up my work today with a couple thin coats of ignition sealer over the cap to prevent this from happening again as noted in the post above.

Needless to say, I was pretty happy today to get mine running without fighting with a distributor cap. Hopefully this helps someone out as a relatively quick and easy fix!