A ‘textbook example of a wet ignition’

As mentioned in this space the past two weeks, Bob Sikorsky has retired from writing the Drive It Forever column and Mike Allen has taken over his duties.

Dear Mike: My car won’t start on rainy days. If it dries out and warms up later in the day, it’s fine. It is also fine on the coldest days and starts immediately.

I’ve put gas-line dryer in the tank, but it’s no help. The garage wants $89 to diagnose the problem, but won’t promise how much it might cost to fix it.

Help! The last rainy spell I was taking the bus to work for more than a week.

— C.H., Boise, Idaho

A: This is a textbook example of a wet ignition, in which condensation builds up on the ignition wires in high-humidity conditions.

Normally the insulation on the wires and coils is sufficient to keep the 20,000-plus volts of the ignition spark inside the wires and convey it to the spark plugs. Older, degraded and dirty wires insulate less and leak voltage, however, and eventually your car won’t start. The high current drain of the starter motor lowers the voltage, so that the spark across the plug electrodes drops below the level need to ignite the fuel-air mixture.

Here’s a quick way to diagnose this: Some evening when your car is dry and running, use a spray bottle to mist water onto the ignition wires. It should be totally dark out, and your car should be parked in an area away from streetlights. If you see dozens of tiny, blue arcs spider-webbing your wires, you’ve got a problem.

You might try removing the ignition wires one at a time and thoroughly cleaning them with some window cleaner or lacquer thinner to remove any surface deposits. Replace each wire as soon as it’s been cleaned, and dress the wires exactly as they were set by the factory to prevent crossfires from one wire to another. Don’t use any silicone-based products, which might contaminate your oxygen sensors if ingested into the air intakes.

If this helps, it means that your wires are near the end of their service life, so it’s time to start saving up for a set of new ones.

Dear Mike: My wife’s Sebring has chrome wheels. Recently one of the tires started losing air on a regular basis.

The service-station manager tells me that he has seen this a number of times: The inside of the wheel, where the tire bead sits, is pitted, allowing air to escape. Is this as common as he suggests?

He wirebrushed the interior of the wheel to smooth it out. Is there a more long-term solution?

— L.L., Mamaroneck, N.Y.

A: This problem is pretty common in any area near the ocean, or where salt is used on the roads. Moisture, aided by corrosive salt, can peel chrome and paint off the rim.

Wirebrushing, to remove any corrosion, is a short-term fix. My preferred long-term repair, for chromed, aluminum, alloy or painted-steel wheels, is as follows.

Start by power-wirebrushing the bead-seat surface of the rim down to bare, shiny metal. Remove every vestige of corrosion you can. If the wheel is steel, use a conversion coating such as Naval Jelly to remove any rust lurking in pits in the surface.

Better yet, sandblast the surface to get the rust lurking in the pits. The iron-to-rust process is self-catalyzing, and doesn’t need any water to continue after it’s started. Never sandblast alloy wheels, however, as it will weaken them.

Now coat the surface with paint. I use a zinc primer on steel, followed by a coat of enamel. Apply an epoxy clearcoat to alloys. Allow the surface to dry thoroughly.

Mount the rims with a waterless mounting lubricant, and be sure to fill the tire with nitrogen or moisture-free air to keep humidity low inside the tire.

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