Wet Weather Woe

[AugustneverEnds]

Summer 2017 has been an extremely rainy one so far around here. Unfortunately 10287 doesn't seem to like that so well. This morning it fired up just fine and idled for a minute and then as soon as I began backing up it died, no sputtering or anything, just dead. I cannot restart it. This is the third time this has happened this year. Each time it has followed a similar pattern, it has sat outside for hours under heavy rainfall, started and then died and only able to restart after drying out. I have driven through several heavy showers without any hiccups though. If the engine is dry and then it gets wet no problem but only when the engine is wet and cold does this issue raise its head. I strongly feel this is a spark problem because hitting it with starting fluid doesn't help. I replaced the spark plug wires this April so I feel confident those are alright. The ignition coil was replaced in 2013. I am thinking maybe I have a small crack in the distributor cap? Any other ideas?

[AugustneverEnds]

Well the rain just eased off and I went outside armed with a hair dryer pointed mainly at the distributor cap and it started and is running okay. I think I am going to let it warm up for a few fan cycles and then do a test run around the block.

[Rich]

I think you're on the right track. Good sleuthing with the starting fluid and detailing the failure pattern. Extra questions here:
1. Do you have the black cover correctly in place over the ignition coil and bulkhead connectors?
2. Is the ignition coil-to-dist.cap wire also new, not just the spark plug wires?
If yes to both then the cap remains as the prime suspect here.

A small crack in the dist.cap can be a particular place for moisture to condense overnight (inside or outside of the cap) even if the rain doesn't hit the cap. Together with some contamination along the crack it can be enough to send the spark to ground instead of to the plugs. With the engine running things get better since condensation is less likely on a warm/hot cap.

Recommend you carefully pull the cap so as not to wipe off any contamination/traces down the sides of it, then inspect inside and out looking very closely for signs of cracks down the side. And hope for some sunny days there soon.

Slight chance that a post-inspection cap cleanup alone might help - unless you find any crack in which case you know what to do.

[AugustneverEnds]

The black cover over the coil and bulkhead connectors seems secure (as secure as they get on DMC-12s) I didn't see or feel any wetness there.
The coil to cap wire was replaced this year so I am confident that one is alright.

I drove the car one mile to work in the rain without trouble, covered the engine with a Hefty bag, worked for five hours and then drove ~40 miles here and there in the dry without incident.

I have an extra cap in my parts stash so maybe tomorrow I will swap it, wait or the inevitable rain, leave the car in the driveway and see what happens. Thanks Rich for the tip about contamination, I will be sure to be careful about that.

[sdg3205]

I had the wet weather woes too. It was solved with a new cap, rotor and wires. I left a nice bead of dielectric grease around the base of the dizzy cap to help keep water out.

[RamblinDMC]

I had a similar problem and my distributor cap had cracked completely in half!

[David T]

I had a similar problem and my distributor cap had cracked completely in half!

Typically you should not have any problems with wet weather with your distributor (cap or rotor) unless it is old, cracked, or carbon-tracked. Same goes for the ignition wires. They usually seal well enough but when the get old they allow water to get into the spark plug wells and then the plugs short out. Bottom line, if you are having problems in wet weather it is probably time for a tune-up and replacing the cap, rotor, ignition wires and spark plugs.

[AugustneverEnds]

Follow-up: Changed the distributor cap last Saturday and of course we had the driest week since September 2016 around here. At last it rained heavily last night so I let the car sit out and get wet and today it started right up and ran like a charm. I'm going to declare case closed and solved.

It's hard to see in the pic but outlets 1, 5, and 6 had grime in there. Numbers 1, 4, and 6 looked a little chewed on enough to allow moisture in I guess.