Why might a 97 Astro van not start when it rains but will start after everything is dry from the heat?

Answer 1

Change your spark plugs, your wires, cap distributor and rotor. I'm pretty sure your problem is there.

This just happened to me. Before you change your plugs, wires, and cap, try this first. Pull the cowling (engine cover) off, locate the 'ignition coil' and try to start the engine. Look at the coil and check for arcing. Race the engine a little to see an arc. I replaced the coil, and the problem was solved.

I had this exact problem with my 98 Astro Van, for a number of years. When it was very damp outside (lots of dew or condensation) the Van wouldn't start. When it was dry, it would start well. --> Eventually I found the problem. The ignition coil was defective, i.e. it had a crack in the coil case. When it was damp out, the coil case would become wet, and the electricity would short (arc) to the coil frame. Hence, no electricity would flow into the distributor, or plugs, etc... When it is dry, it is harder for it to short to ground, so the cracked coil will work (somewhat). To check for this, try the following when it won't start. Lift your engine cover off and locate the coil. Make sure the wire (coil to the distributor) is firmly connected at both ends. Turn the key and watch the coil. If you see blue-white electrical arcing, you have a bad coil. I changed mine over a year ago, I have never had this problem since. Note: For this specific problem, change your coil before you spend money on plugs, wires, etc...