won't start after wet night

After overnight rain my SuperS fires about 3 times and floods. Previous threads have suggested a crack in the dizzy cap. The RAC guy who last got me going said there was no error light message. As a temporary measure I have taken to covering the engine with a towel overnight, and that works fine. Before I go & get a new dizzy cap, is there anything else I should check.

Took the cap off the dizzy yesterday. Some clown in the past thought it only had two screws and there is a crack around the third screw. But no evidence of the spark tracking out that way. There was also a big build up of some grunge - zinc oxide? - on the inside terminals. Chipped that off with a screw driver, polished the surfaces with some emery paper. Polished the outside contact of the rotor with emery paper too, for good measure, gave the inside of the cap a blast with WD40 and wiped it clean and dry. No sign of any other cracks. Runs noticeably better. Will see how it starts after the next overnight rain and post the result, but I'm sure that grunge was the problem.

if the dizzy cap is cracked you might as well change it as they are only cheap.

Started beautifully after a couple of wet nights so I'm sure that build-up of grunge was the problem. Possibly partly a result of frequent parking at the beach? At least worth a look for anyone else who gets the same problem. The crack is only around the mounting screw but I'll change the cap soon anyway.

were you getting the problem of the car satrting and stalling soon after. just had a wet couple of nights here and started my car this morning and it idled at around 250 rpm and battled for about 30 sec and then stalled. started it a second time and it stalled then after holding it at 1500 for a minute it sat at the right idle... would this be the dizzy? or would it be a problem with the auto choke thing.... cos usualy when i start it it idles at around 1100 untill its warm...

cheers, tris

can someone explain as to why this would only happen on a wet night. I dont see that being the cause as water is not actually getting under your bonnet?

i was thinking maybe water in the air?? being damp... maybe?? condensation?? i duno... but this arvo started it after it had been in the sun for a bit and it started fine... still starting from cold engine..

Mostly it would fire about 3 times and then nothing. The computer apparently thought it was firing but still detected too much oxygen in the exhaust, so injected lots more fuel, flooding the engine. When the RAC guy pulled the plugs out they were visibly wet. Turning the engine over with the starter and foot flat to the floor would eventaully get a few more fires, then running on one, then two, maybe 3, and suddenly back to normal, unless the battery went flat first. On the last few occasions, it ran about half a kilometre and then died again. But more of the same got it going again, then OK for the rest of the day.
Water is a lousy conductor unless it contains ions - dissolved salts. Oxides, like the build up on my inside terminals, are even worse, effectively insulators. But zinc and copper oxides are also hygroscopic, so they draw moisture out of the atmosphere. Being warm when you stop the engine, the air under the bonnet holds a lot of moisture. As it cools down, it condenses out. More so when the humidity is high, like on a wet night.
Putting a towel over the engine at night absorbed a lot of moisture from the air under the bonnet - it was usually a bit soggy in the mornings - enough to stop the problem, temporarily.
My reason for writing the follow-ups is that other people obviously get the same problem, but rather than rush off to get a new dizzy cap, I think it is worth at least looking at the old one. You have to take it off to replace it anyway so why not? Make sure you undo all 3 screws, and check that the inside terminals are shiny clean on the sparking surface. The spark can jump around a bit of build-up, but eventually it gets to be just too much.

same thing used to happen to my micra, used to spray the cap with water disperser and it would start straight up, or park it where the sun hits it first thing in the morning, was condensation and moisture rising from grass on cold/wet nights (was fine if parked i the shed) eventually started seeing the spark come from the distributor cap from a very fine crack that even my mechanic couldnt find. They told me it was my battery and charged me for a new one, but i kept telling them it was nothing to do with that. goes to say that I was right and never had a problem again after my cap was replaced! kept it going for a few months with the spray approach, so if it starts again, you can give that a go!

4 year update! First cold wet morning in ages, and she wouldn't start again. Fired once and flooded. First time since replacing the dizzy cap, which I haven't touched in the meantime, but someone else may have - the rubber seal was not seated properly and a loop of it was hanging out. I'm sure I didn't leave it like that. Whatever. Inside was clean and dry, but once again, a build-up of white oxide on the inside terminals. I cleaned that off with a points file and polished up the terminal on the rotor for good measure. Cold and wet again this morning, but she started fine again.

I also managed to overtighten the 3rd screw, which is a bastard to access, and sheared it off. Bugger! It can stay that way for a while.

I was worried the other day when it was raining so hard the road turned into a river and thought I was going to get washed away lol.

My car did get washed away then manage to grip the road. went side ways for a while. did a little poop in the pantz....hahhaha

Mine does the same, i hold a lighter under the bottom of the cap and run it back n fourth n heat it up a bit, always works lol