Tough to start after rain, and oil in one spark plug

[flinters17]

I've got an '89 JDM Master Ace / Van which normally runs like a top. However I'm troubleshooting a new issue where my van doesn't like to start after a heavy rain. It has happened twice now and I thought the first time was due to bad gas as I hadn't driven it in about 2.5 months. I put in some Heet and she fired right up. No issues until after a heavy rain, and again I couldn't start it. This time it had only been 2 days since I last used it, so not the gas. I tried to determine what the common factor was and realized it was right after heavy rain or a long period of rain.

I recently replaced the spark plugs and noticed oil on the 4th one that I pulled out. Double checked the gasket and sure enough, old and tired. Ordered a set to replace but haven't been able to do the work yet. I'm curious if this is part of my issue above?

When trying to start, the starter cranks without slowing. I haven't officially tested the battery but I don't suspect it right away.

I'm also suspecting the coils. I haven't tested those either but the current set appears to be original so I decided to get a new set to replace, or have as spare.

Any other thoughts on what the issue could be?

[Burntboot]

Oil in a spark plug well won’t cause a starting problem in the rain.
There is only one coil and it lives inside the distributor.
There is a thread in history that is almost identical to this one.
A quick search should bring it up.
I am technology challenged today so can’t do it for you.

You’re getting moisture inside the distributor.
Could be the cap, gasket, wires or maybe all of the above.
Other possibilities exist, but best to check the easy maintenance type stuff first

[flinters17]

Thanks! Learning as I go so sometimes I see a problem and assign it to something else haha.

Replaced the spark plug cables this weekend, and those well gaskets since I was in there. I've also been coming out to dead batteries on occasion and after a really cold week it was fully dead. Not sure the age of it but it has "2015" written on it so I'm guessing at least 6 years old. So I've got a new one of those coming too. Distributor cap looked good from every angle I could see it. I did notice that the connection from the distributor to the cables was a bit looser than the new one, so maybe that was part of my problem as well.