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Combustible Debate Over Carburetors

June 25, 1987|RALPH VARTABEDIAN | Times Staff Writer

Question: I am preparing to buy a new car and am wondering whether fuel-injection systems are less reliable than a carburetor. --T.B.

Answer: Fuel-injection systems, which are increasingly in use by car manufacturers, have had notable problems, but the equipment isn't always at fault. Contaminated fuel can clog fuel injectors and lead to costly replacement service on the injectors.

A fuel injector replaces a carburetor in the function of delivering a mixture of fuel and air to the cylinders of the engine. Fuel injectors are considered more efficient in metering out small amounts of gasoline for maximum performance and fuel economy, but they are expensive and costly to repair.

A carburetor works passively, by allowing the stream of air going in to the engine to draw and atomize gasoline through small passages inside the carburetor body. The concept is quite simple.

A fuel injector operates actively by squirting a small quantity of gasoline directly into the intake manifold near the cylinder. The amount of fuel injected into the engine is controlled by a computer, which receives sensor data on such things as air temperature, engine load and engine speed.

There are various types of injection systems, but the most current version has an injector near each cylinder, all controlled by a central computer.

Fuel injectors have been terribly unreliable in past years, but their record is improving. They are still subject to clogging because they require fuel that is much cleaner than that required by a carburetor.

A clogged injector that must be replaced will cost about $40 at the low end of the price range, and replacing all of the injectors on a six-cylinder engine can get quite expensive. If the computer or other parts need replacement, you are facing a potentially very high repair bill, going into many hundreds of dollars.

That's not to say that carburetors don't fail. They also can become clogged and require refurbishing. Typically, a carburetor can be repaired or replaced at a lower cost than a major overhaul of a fuel-injection system. In addition, the vast majority of mechanics are much more familiar with carburetors.

Q: Is it legal for a car dealer to sell a 1988 demonstrator with 1,000 miles on it as a new car?--C.S.

A: In a legal sense, a demonstrator is still registered as a new car. But any car with 1,000 miles on it is not new in a practical sense and should not command the same price as other new cars.

A car's service life is generally considered to be 100,000 miles for accounting purposes, although most cars will operate substantially beyond that. A car with 1,000 miles on it has already given up 1% of its service life and has depreciated in value much more.

I would expect to negotiate several hundred dollars off the price of a $15,000 car with 1,000 miles on it. But you should exercise some caution. I have no doubt that the miles on these cars are far more severe than those put on by most new-car owners.

Q: I bought a 1986 Chrysler Fifth Avenue, which has a very bumpy ride. The dealer installed rear shocks and suggested that I have the car undercoated. I paid for the undercoating (the shocks were free), but the problem still persists. Do you have any suggestions?--J.A.M.

A: I suggest you find a new dealer. An undercoating will do nothing to help smooth a ride, though it may help to dampen the noise level inside the car.

Shock absorbers are one factor in determining how bumpy a car feels. Tire pressure, spring loads and the overall design of the frame also count. You should find a good front-end mechanic to examine the car, but be prepared to accept the car's ride as it is now.

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