TOTALLY GEEKED!

Felicia's Car Can't Take the Heat

Dear Car Talk:

We live in the Southwest and have a 1992 Lincoln Town Car, which is much loved by my husband. The only problem is that it likes to die when the temperature is above 96 degrees. We will be traveling for over 30 minutes and boom, it dies. It starts again in about 20 minutes, but if it is still hot, it will soon die again. This also happened once in cooler weather when we had been driving in the mountains for two hours. We've been given theories such as vapor lock and boiling fuel, and advice that included clothespins, but I don't feel comfortable betting my safety on clothespins. I hope you can help us. Thank you.

-- Felicia

Don't discount clothespins, Felicia. I always keep a couple in the glove box. I used to clip them on my nose whenever my brother was in the car. 

Clothespins aside, your first step is a little detective work. In order for the engine to run, it needs three things: Air, fuel and spark. I'll assume that air is not a problem, since you continued breathing long enough to write to us. So you have to determine whether the engine is dying because it's losing fuel or losing spark. 

If you were one of our customers, we'd lend you a little inductive test light and show you how to use it. If you open the hood and just touch the probe of the test light to any of the spark-plug wires while the car is running, the light will flash, indicating that electricity is pulsing through those wires. That tells you there's spark. 

What we'd instruct you to do is, next time the car dies, open the hood and touch the test light to a spark-plug wire. Then have another person try to start the car. If the light flashes, you're getting spark. That means the problem is fuel. 

If you try to start the car and the test light doesn't flash, then we know it's a spark problem. By knowing which of those it is, we can save you a lot of time and money in trying to figure it out. 

If the test tells us that the problem is lack of fuel, we'd suspect either the electric fuel pump or the fuel pump relay.

If you had no spark, we'd suspect one of the electronic ignition components, like the electronic ignition module, the coil or the hall-effect sensor.

But start by finding a mechanic who's willing to work with you to narrow it down. If you need help finding a mechanic you like, try searching our Mechanics Files, which is a database of mechanics who are personally recommended by other readers and radio listeners of ours. Good luck. 

-

• 3 comments Comments

jakdedert• 6 hours ago

This has been an ongoing problem in my '98 Mercury Villager (Nissan Quest). I've finally, through research and experiment, tracked it down to a faulty fuel pump. There was a recall for the years before '98, but for some reason, they thought they had fixed it in 1998. They had not. Mine has had the exact same symptom, since I got with less than 80k miles.

Basically, when very hot, the fuel cavitates in the pump. Filling with cool fuel solves the problem, unless the temperature is very hot...then the cure is short-lived. I can tell by the 'note' of the fuel pump whether it's going to start or not. In a pinch, if I can park in the shade, I can wait until I hear the pump begin working again. Until then, trying to crank the engine will be a waste of time.

Cooldude61• 8 hours ago

The most heat sensitive problem on most american cars is the Ignition module. Check the module if it conks out after running a while and starts normally after cooling down a bit. It could be the other things Ray mentioned as well but the module usually is the most likely suspect.

jfbramfeld• 10 hours ago

I had that happen with a mid-80's Oldsmobile 98. Identical symptoms. It turned out to be the electornic ignition control module or whatever they called it back then.