97 truck won't start when damp outside

97 Chevy Silverado will not start when damp outside. Tries to start. Once started runs fine and will start up easily as long as it has not set overnight. Getting worse. Used to start when garaged. Heat the garage and it will start fine. Have replaced cap, plugs, wires. No luck.

Scan it and look at the coolant temp readings make sure it matches the air temp when cold , also check fuel pressure as the key is first actuated, make sure the pump is up to spec, partially clogged fuel filter can contribute to this also.

did you replace the coil wire also?

try your distributor cap.
my old avalnche did the same thing on cold days, or rain.

If a tune up dosent work try the ignition coil. I had the same problem in my 93 gmc 1500. Hope this helps.

Sounds like a cracked distributor cap. Pull the cap after it has sat outside a good while and check for condensation. If the inside of it or the distributor is wet, the cap is bad..

make sure your distributor cap hold down screws arent loose or the tabs on the distributor where the screws thread into arent stripped cracked or completely broken. the distributor housing is all plastic. i had this problem with my 97 2500. if it is broken try to fix it yourself if you can. a new one goes for about $300 at the cheap parts store