Has My Chevy Lost Its Spark?

Dear Car Talk

Dear Car Talk | Aug 26, 2019

Dear Car Talk:

I have a 2002 S10 Chevrolet truck that very often won't start when the weather is damp -- summer and winter, in the garage or out.

Blowing under the hood with a hair dryer sometimes does the trick, but it's not convenient.

I have had it in to a couple of shops for repair, but they can't find the problem. I have had the battery and the distributor cap replaced. Any other suggestions? -- Caroline

You need to install one of those big, car wash car dryers in your garage, Caroline.

Then, you'll just flip the switch, and the car, the garage, and probably the whole driveway will dry out in no time. To save time in the morning, you can even stand under it and dry your own hair. As long as you're OK with a severe "down-do."

I'm going to suggest you try a new set of spark plug wires. That's the most common culprit when it comes to older cars that won't start in wet weather. The distributor cap was a good guess, but obviously that wasn't it.

In older cars like yours, here's how the electrical stuff works: When it's time for a cylinder to fire, your distributor directs a high-powered jolt of electricity through the spark plug wires, to the appropriate spark plug.

The spark plug uses that electricity to create what? A spark! A big spark.

That spark is hot enough to ignite the fuel and air in your cylinder, and that's what makes your engine run.

What typically happens with older spark plug wires is that the insulation surrounding them breaks down. And since water is conductive, when there's moisture in the air (or perhaps even condensation on the wires themselves), electricity leaks out on its way to the spark plug. If enough of it leaks out into the moist air, there's not enough power left to make a good spark, and your car won't run.

In fact, if you open the hood and get a friend to try to start your car on a damp evening, you can sometimes actually see a blue glow of electricity coming off of old plug wires. That's your power leaking away.

So, try a new set of spark plug wires. And don't be cheap. Either go to the dealer, or ask your mechanic to get you a set of OEM (original equipment manufacturer) plug wires. They're worth the investment.

If that doesn't fix it, then a bad coil would be my next guess. But at that point, you'd be guessing, which can get expensive

. You'll want to seek out a mechanic who's a little more interested in helping you than the last two shops you visited. If you can't get a good recommendation from a friend or family member, pick a top mechanic from www.mechanicsfiles.com, where our readers and listeners have shared the names of their favorite repair people.

Good luck, Caroline.

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