1985 f150

This truck runs great EXECPT in high humidity and rainy days. When such it is very difficult to start. It will turn over a few times then “lock up”. When it does crank it skips terribly. I suspected a vapor lock (changing atmospherics etc…) but was told it was most likely a spark plug issue.

I’m a decent shade tree mechanic but dang if I’m not stumped. Little help please

I sounds like an electrical issue to me. When was the last time you replace the distributor cap and wires?

new plug and wires 12 months ago

Distributor cap? I would try that next.

$11 for a new distributor cap and it cranked on the first turn DURING the rain.

thank you