1991 F150 won't start when it has been raining...

[melbs]

Edit: I have found the last couple of long hard rains here my '91 F150 Lariat won't start, it turns but will not fire up. The battery gauge shows below 12vdc but I know the battery is good. The truck starts up any time it has not been pouring rain. It does't happen on a light rain, it has to be an all day rain.
The plugs and air filter are new 3 months ago, I am not sure where to start....Someone mentioned it could be cap and rotor b/c that is what happens with their Jeep.

Thanks in advance for any help!

Scott

[melbs]

Voltage on battery shows 12.4vdc when off, 14.0vdc when started so the alternator and battery should be fine.

[john roberts jr]

i had the same problem with a 92 ford f-150. I found that the ign coil was the cause. When the weather is clear start the truck and, and using a spray bottle spray on the coil. If the truck dies, then start there. I hope this helps, If any questions feel free to write back.

[melbs]

Thanks for the tip. I replaced the cap and rotor and it is running real nice now, it rained yesterday and it still started so I am feeling pretty good that it is fixed...if not I will check the coil next.

Have a good one!

Melbs