Failure to start

About every six months, during or after a rain, my 98 astro van fails to start. The first time the mechanic replaced the fuel pump as there were no gas fumes. After it sits for awhile it will start with no problem. When I have it towed to the garage it always has started for the mechanic and the computer readout shows nothing. HELP

There’s two ways an engine fails to start. You turn the key and nothing happens, or you turn the key and the engine cranks over but doesn’t start.

Tester

The problem is probably moisture on spark plug wires and / or on wiring controlling the ignition coil. Replace the spark plug wires.
When it’s damp outside, play heated air from a hair dryer over the top of the engine. Attempt to start. Results?

You must find out if your Astro really is not protected from moisture. Cars are designed to be driven in the rain, what has made yours the exception?

As a mechanic I would note your observation, I would not let it direct my diagnosis.

A 98 car with original plug wires would be a prime suspect for new wires.