My car has a brand new batter, and alternator. It never starts when its wet outside/raining. It usually starts with a jump but today it didn’t. Help! Why does my car do this?
Your ignition system has to be gone over. Typically these no starts in wet weather point to cracked wires or other leakages.
A new battery and alternator can’t help you there.
Spray the spark plug wires with water. If the car stalls or misses,you found your problem. Better to do this when its dark outside because you will probably see some arcing.
If it has a distributor cap, look inside. Moisture can get in there and condense; especially if the thin rubber ring between the cap and the dist body is missing or dislodged, or if the o-ring on the dist shaft is compromised, letting crankcase vapors into the cap.
Please explain your no start problem. On a wet day does the engine try to turn over but not catch or is there no sound from the engine? If the engine tries to turn over the folks above are spot on.
Shanoia is correct about moisture getting inside the distributor cap. Dry it out and spray it all down with WD-40.
Another option is to blast the distributor cap with a hair dryer for a while. That’s a short term solution.