S-10: Smooth idle, ran rough, now won't crank
 

Help? Chevy S-10 Pickup - was running rough, so in March, replaced plugs, wires, coil, distributor cap/button. Ran much better for about a month, then began running rough again.

Idle is smooth... Most times runs rough - not always. Seemed somewhat rain related till the other day... had rain, truck ran fine.

Today, heavy rain. Truck turns over, but won't start. Almost every time I turned the key to off, I felt a hard jerk in the body.

Also, fuel pump was replaced less than a year ago. I've ran STP thru it several times without effect. Ideas?