2000 GMC Safari runs fine in dry weather, but will not start during wet weather.

jayar44

I have noticed that if vehicle is used every day, it seems to start okay, but not consistently. It turns over while trying to start, and I hear the fuel pump, but will not start. After the pavement dries up and humidity goes down, it starts up right away. A couple of times it took the second attempt to start, but usually on first try.

fg712000

Had one a long time ago that had the same problem. It ended up being a hairline crack in the distributer cap. I could barely see it even after I knew where it was.

thecardoc3

What is the maintenance history, especially "tune-up" items? Moisture getting into the distributor cap is one possibility, but anywhere that the secondary insulation is weak can be giving you problems. It might be wise to plan on doing the whole job. Replace the cap, rotor, wires and the spark plugs.

There could be other issues and it would be wise to prove that you don't have spark during a failure. That is easily done with a spark tester that takes about 25K volts to get it to fire. The ST-125 works well for this test. http://www.amazon.com/OTC-6589-Electronic-Ignition-Tester/dp/B0050SFVO2/ref=sr_1_4?ie=UTF8&qid=1451227073&sr=8-4&keywords=spark+tester

Even if the engine runs, if the ignition system cannot make the spark jump this tool, diagnose as no-spark.