I've got a Chevrolet van that doesn't run when it's wet out. Earlier mechanic had done some diagnosis and looking around in the wiring harness that goes from the engine to the computer.
Makes me wonder if there is water getting in to the wiring harness, and that's what makes it not run when it's wet.
What's a good way to seal this, to keep water out? Duck tape? Scotch 33 electrical?
What doesn't run about it? Does it crank? Normal speed of cranking?
Does it ignite at all?
If it turns over and there is no ignition, the usual source is wet spark plug wires; wet distributor cap, inside or out; or wet ignition coil.
Shops don't want to spend forever on the repair, or worse yet, give it back to the customer and have it not work again, so they just replace all three, and the rotor too.
But if you're doing it yourself, and you don't absolutely have to start the van on a given wet day, you can replace one thing at a time. Buy the parts at a consumer parts store, where you can (check on this) return an unused distributor cap or coil. Pro stores don't like returns on electrical parts, and Pep Boys etc. might not allow it either.
It's also possible that 2 or 3 things contribute to the problem. I found it hard to believe the coil could be wet inside, until after replacing the wires, I replaced a coil and everything was good again, even in wet weather.
Yeah, on a dry day I'd take the cap off and let it dry out in there, but the problem is more likely the spark plug wires if they are 6 years old or more. I guess the rubber covering is porous. Replace them one wire at a time, both ends, so you don't mix up which one goes where.
Probably condensation under the distributor cap. VERY likely if the vehicle isn't driven daily. The moisture burns off when you drive them daily. Pop the cap off, wipe it out with a towel with some silicone on it. Then spray the wires down with silicone. If you think it's in the harness you can spray the back of the plugs and wiring with clear enamel paint. It will seal the wiring.
First things first - good spark plug wires. You have the potential for 60,000 volts there - that voltage will leak theough anything that is not perfectly waterproof. New wires with silicone dialectric past in the coil boots and the plug boots (and distributor boots if it still has a distributer)
12 volt wires don't leak appreciably through insulation that is wet or dry. If they are going to short wet, they will short dry too. Low voltage (sensor) connections are working on 0-5 volts - so again, moisture won't short them. If anything, take the connectors apart and clean them. A bit of dialectric grease hear usually won't do any harm either and will keep moisture from getting in and corroding connections. Moisture on low voltage stuff is more likely to cause corrosion and open circuits than shorts. The new plugs we've been telling you to put in for the last 2 years will help too as the wide gap and rounded electrodes of worn plugs requires a lot higher voltage to jump the gap. A good sharp well gapped plug will hold your secondary voltage down around 45000 volts - a lot easier to keep in your wires. Also make sure the cap, if a distributor model, and / or the coil towers are prisinely clean..
Thes steps will make even a 6 volt chrysler flathead start with a water hose pointed at it.
Saturday. Went under van. I was tracing out a blue wire, Spirit said to look at the tan one. The tan wire had broken next to a crimp butt connector. I cut that out, and used a wire nut to put the wire back together. Try the key, van starts up nicely.
Several layers of Scotch 33 electric tape go over that. And some tie wraps.
Thanks to all who suggested sealing tape for the wiring harness.
Wire nuts and common insulated crimp connectors are not good ways to patch wiring harnesses. A good solidly twisted inline connection (kinda like the old "western union" splice, soldered and sealed with a 2 inch sleave of heat shrink (possibly also sealed with dialectric grease) makes a connection that won't corrode and will withstand the moisture that is always a problem under the floormats of ald vehicles.
soldered and heat shrinked. In this case, I think the wire nut and tape are better than the butt crimp that I took out. The butt crimp lasted several years.] n" splice, soldered and sealed with
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