Why can't autos use natural gas?

Q: My boss and I were discussing alternative energy and we came up with the same question. Is there a movement to use natural gas instead of gasoline in passenger cars? From what little I understand, engines would not need too much modification to do so.

A: You are correct. Modern automotive engines and engine management systems need very little "adjustment" to operate on liquid natural gas.

Vehicles designed, built or modified to do so are called NGVs, or natural-gas vehicles. There's little or no drivability or performance differences between the two fuels, but each has advantages and disadvantages.

The advantages of natural gas are cleaner emissions - lower carbon monoxide, oxides of nitrogen and unburned hydrocarbons - and because of this, perhaps, less maintenance and mechanical wear and tear. Fuel costs are typically more stable and about one-third lower than gasoline.

There may also be a safety advantage because fuel storage tanks on NGVs are substantially stronger than gas tanks on most motor vehicles.

Disadvantages? First and foremost, the availability of liquid natural gas. There are refueling stations, but they're few and far between compared with gasoline stations on nearly every corner. A century of gasoline distribution infrastructure development is hard to beat.

Also, natural-gas vehicles tend to have less passenger room because the fuel storage containers are larger, heavier and occupy more space. That means less range, or miles-per-tankful, than a comparable size/power automobile.

It's also important to recognize that natural gas, like petroleum or gasoline, is not a renewable resource. U.S. natural gas reserves are large but not unlimited.

Several car companies have developed natural-gas vehicles, and a number of municipalities, law enforcement agencies, power companies and other large fleet operators have operated large numbers of them. That said, they're still just a miniscule percentage of the total number of motor vehicles.

Personally, I think the biggest factor is convenience - or lack thereof. If natural-gas fueling stations were as common as gasoline stations, the public would be far more receptive to natural-gas vehicles.

Q: Every few days, my 1995 Nissan Maxima would not turn over when I turned the key. No sound, no clicking, no nothing. The shop replaced the battery, but the next day the same issue. I fiddled around, and then the car started. Took it back, and they replaced the starter. Today, the same thing happened. Please help.

A: Well, you now know the starter and battery weren't the problem, right? Any time a vehicle suffers from an intermittent "no crank" condition, the first suspects, in order of probability, are battery cables, connections and grounds, ignition switch and park/neutral or clutch interlock safety switch.

If by "fiddling" you mean wiggling the key while holding the switch in the "start" position, suspect the switch itself. If you mean wiggling the shift lever within its range of movement in "park" and/or "neutral," suspect the park/neutral safety switch.

If, when the engine won't crank, connecting a single jumper cable from the positive battery terminal and then to the positive terminal on the starter motor causes the engine to crank over - but not start since the ignition is "off" - the problem is likely with the switches and/or harness.

If this doesn't crank the engine over, it's likely a poor ground connection between the engine/drivetrain/chassis and the negative battery terminal. Take all safety precautions before this test by making sure the ignition is "off," parking brake is set and the transmission is in "park" or "neutral."

Paul Brand, author of "How to Repair Your Car," is an automotive troubleshooter, driving instructor and former race-car driver. Readers may write to him at: Star Tribune, 425 Portland Ave. S., Minneapolis, Minn.,55488 or via e-mail at paulbrand@startribune.com. Please explain the problem in detail and include a daytime phone number. It isn't always possible to send a personal reply.