will not start after it rains untill it dries out on 1990 GMC S15

will not start after it rains until it dries out

Asked by for the 1990 GMC S15
Usually a sign of ignition system failure. With the engine running in Park e/brake applied, get a Windex bottle full of water, mist water over the spark plug wires coil and distributor cap, if the ignition insulation is good the engine should stay running smoothly. if the engine suddenly runs rough you may see spark jump or will have instantly found where the insulation of the spark plug wires or cap is failing.