Gas Odors Surface in Warm Weather
Question: What causes the smell of raw gas inside my 1978 Lincoln Town Car on hot days when the temperature outside is more than 70 degrees? I have had the engine analyzed. I have had a specialist check the carburetor. It has been to three Lincoln dealers. Nobody can find any leaks. Still the fumes get into the car, even with the windows up and the air conditioner off. It’s a good car otherwise. It has 75,000 miles on it.--J.J.V.
Answer: Your problem is more likely to be at the gasoline pump than inside the engine. Most cars, especially those built since the mid-1970s with emission systems that capture evaporated gasoline, have expansion chambers at the tops of their gas tanks.
The chamber, which is in the form of a hump at the center of the tank, is designed to provide a small amount of trapped air that can permit gasoline to expand during hot days. If the gas doesn’t have anywhere to expand inside the tank, it will flood the evaporative charcoal canister and inundate the entire vehicle with fumes.
If you constantly attempt to top off your tank when you fill up at the gas pump, you’ll certainly defeat the purpose of the expansion chamber. I suggest you not add any more than a few cents worth of gasoline after the pump has tripped off automatically.
Q: How long should an auto headlamp last before burning out? Mine seem to burn out almost every year.--G.Y.
A: Headlamp manufacturers, such as General Electric, aim for a 320-hour lifetime for low-beam lights and 150 hours for high beam. If the lamps actually hold up that long, you should have to replace the lamps only once or twice during the lifetime of the car.
But in practice, foreign objects will break the lamps or problems in the electrical charging system will cause the bulbs to burn out more quickly. The industry currently designs the lamps to withstand a maximum of 14 volts, but some auto electrical systems can have voltage spikes that go up to 15 volts.
Q: I have a 1985 Volkswagen Cabriolet. At 11,000 miles, the dashboard warning lights started to behave strangely. The VW dealer wrote: “Engine temperature light flashes, then loses tac. Gas, oil and temp gauges work intermittently.” They replaced the circuit plate and the voltage stabilizer, but that didn’t solve the problem. I hope you have some suggestions.--A.C.
A: You most likely have either an open or short circuit. Your mechanic should check the multiple ground connection under the dashboard. The connection may be a poor one, which would explain the problems you have. Otherwise, you have a problem in wire harness, very likely with an open circuit.
Ralph Vartabedian cannot answer mail personally but will respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, You section, The Times, Times Mirror Square, Los Angeles 90053.