Maybe they do melt when they get wet...

Often when this sort of thing occurs, it's moisture in the distributer. I've owned cars where washing the engine area or driving through standing water would sometimes cause cutting out, a non-start or troublesome start/run afterwards. Popping the dist cap off and a spritz of WD 40/wipe out with a rag always fixed the problem.

You might find it interesting to lift the hood when it is dark out, start the car and spritz some water from a spray bottle onto the dist caps and spark plug wires, and observe for ignition sparks jumping randomly. This is an excellent shade-tree test for secondary ignition insulation issues.

 

I do think Mike is right: it's a distributor or a spark plug wires insulation issue.
This said, to prevent this is a good thing to put a thick tarpaulin directly on the engine before washing the car. And remember to remove it, or the car will catch fire when you will restart it...

I always do that before washing my cars.

It would be a good idea also if you leave the car outside and there is a rain possibility.

No problem if it rains when you are driving the car: engine heat will make the water evaporate

ciao

 

The distributors should have rubber boots (part number 118889) to protect them from moisture. Some cars are now missing the boots/covers.

 

Best not to wash them at all - it just shows up the rust.

 

The single distributor 308’s have a shield that sits over the distributor itself. And an additional shield built into the deck lid. Image Unavailable, Please Login

 

It’s a rubber piece that completely covers the distributor itself, similar in composition and design to the covers over the ignition coils. The spark plug wires feed through the boots. There is a picture of the part on the Euro Spares site. Just enter the part number and search.

 

1978 308 GTS

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This is the correct shield if you have the attachments where the shield mounts to the firewall. I need to find one. Any suggestions?

 

Give up on using water at all....there are so many Speed Shine type products, that spraying thru our vents into the spark plug well seals is just asking for it..

And as you see, you got it!
IMO once the seals are aged, they let water run in, and from there it cycles as steam back into water and rusts everything in the spark plug well.....spring steel contacts in the wire extenders, the plug itslef....

 

That's only for the Euro 8 point distributor, please realize...

 

I used to put a piece of heavy plastic over the engine and also in the front before I washed my Ferrari to keep the water out. It did the trick would keep everything dry.

 

I use a polyester shower curtain over the engine - Even though technically the car is having a bath!

 

Does anyone have a still original car with it’s still original fixings for the distributor shield - I know it’s a bit retentive, but I’d be interested to know if there is anything “unusual” about the washers used under the nuts, and under the bolt head (4-off total)?