Engine won't start when rainy?

Hello,

Many of these 4.3L engines suffer from this issue.
It is usually caused by moisture in the distributor or the coil pack.
I have seen in many of these coil packs will get moisture in them when it is very humid, due to poor seal around the coil.
Typical fix is to replace the coil.
You also need to open up the distributor cap and look for moisture damage.
Clean it out and replace with new o-ring for the cap.
Be sure to inspect the ignition control module as well.

https://www.2carpros.com/articles
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I have attached the diagrams for your reference.

Please let me know of any questions.

Thank you.