Toyota Repair: Wont start after it rains, path of least resistance, distributor caps

Question
TRying to help a friend out before he just spens a lot of money without knowing what might be the issue. Vehicle is a 1981 Corolla. After it sits for awhile (like when at work) and the humidty is high or after it rains the car won't start. It cranks fine, but won't turn over. If you wait until its warmer it works fine. He's ordered a new distributor, rotor and wires. Plus a fuel pump. So basic questions is: Why will it start sometimes but not when its been wet outside?

Thank you

Answer
High humidity has a tendency to short circuit weak electrical components at their insulation, especially spark plug wires, distributor caps, coils etc. These are all in the secondary high voltage circuit, so to answer your question as to why this happens. Electric current will always follow the path of least resistance, for instance if the spark plug wires are old and the insulation has small cracks they will tend to arc to whatever ground it can find, this is aggravated if the humidity is high(water makes an excellent conductor)so the current instead of going to where it is supposed to will just take the easy path to ground and there will be no spark at the spark plugs.
Your friend is on the right track, this is an electrical problem so I'm not sure if the fuel pump is needed but let's face it, it's an old car, the pump is cheap and it's good insurance.