Driver’s Patience Is Running on Empty Because of an Unreliable Gasoline Gauge
Question: As technology advances, why is it that gasoline gauges are still so prone to error? I can’t tell reliably when I have 2 gallons of fuel left or when I have zero fuel left. If I knew for sure, I would spend less time filling up my tank.
--J.M.
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Answer: Supposedly, gas gauges are getting more accurate, though they may never be reliable enough to report when you have less than a gallon left.
Since the Flintstones, gas gauges have used floats that ride on top of the fuel in the tank and a rod to connect with an electronic sensor unit. The big drawback to the float-and-rod system is that a given change in the volume of the tank doesn’t translate to a proportional movement of the rod. So after you fill the tank, the needle on the dashboard stays on “full” for too long and then drops rapidly.
The opposite can happen when the tank is nearly empty. That’s when you want the gauge to be the most accurate, but the float and rod often don’t have a full range of motion. So the needle may hit empty when there’s still 2 gallons or more in the tank.
Unusually shaped gas tanks also can trick the system, because the rising and falling of the float are not proportional to the amount of fuel remaining in the tank.
Microprocessor control on newer cars is supposed to improve the accuracy. Software can account for unusual tank shapes and compensate for the sloshing that occurs when you go around a curve or up and down hills. But you may run out of gas if you think even these microprocessor systems can be accurate to a gallon or less.
The best bet for watching your fuel is still the oldest: Reset your trip odometer each time you fill up and calculate about how far you can drive on a tankful. If your car gets 25 miles per gallon and you have a 16-gallon tank, in theory you can go 400 miles. But you might still want to leave a little reserve, because mileage can vary from day to day based on the kind of traffic you encounter.
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Q: What’s wrong with the radiator system on my 1990 Nissan Maxima? The reservoir tank fills up with coolant and overflows. When the engine is cool, it takes about a gallon of fluid to fill the radiator back up to the top. This has happened a couple of times. Also, the heater takes a long time to provide heat even when set on high.
--B.W.
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A: The engine seems to be overheating and spilling coolant out of the reservoir. Another possibility is that you somehow are losing fluid, which is causing the overheating and the subsequent overflow from the reservoir.
You ought to check all of the components of the cooling system: thermostat, water pump, hoses, radiator, radiator cap, cooling fan and the engine temperature gauge itself. Your best bet is to find a good radiator specialist.
If you don’t normally see engine coolant leaking when the engine is off, then you may have an internal breach of the system, possibly a head gasket failure. That’s a worst-case scenario.
What may look like a head gasket failure may in fact be something less problematic. In 1995, Nissan issued a technical service bulletin alerting dealership mechanics to the possibility of leaking from a cylinder head plug behind the timing belt cover. The repair procedure, as reported by the Alldata automotive information service, simply calls for removing the plug and using Teflon tape or another thread sealer and then reinstalling the plug.
If the plug or the head gasket itself is not the problem, you probably will want to start with the cheapest item, the thermostat. If it is not opening at the proper temperature or opening all the way, it can cause the engine to run hotter than normal.
In addition to the thermostat, you will want to make sure that the coolant and heater hoses are not collapsed or blocked, that the coolant fan turns on at the correct times, that the radiator cap allows the system to pressurize properly, and that radiator passages are not blocked.
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Q: I bought a new Nissan pickup truck with all kinds of stickers on the body that I don’t much like. I managed to peel them off with my fingernail, but with a couple of the larger stickers there seemed to be some sticker glue left on the body. Can you tell me what to use to remove the glue?
--L.C.
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A: You might start with acetone, a solvent that can break down a lot of adhesives. But before you start, try a test patch on an inconspicuous spot on the paint to make sure the acetone doesn’t damage the finish. Generally, acetone is safe to use on paint; mineral spirits also might work.
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Q: My 1983 Honda Civic wagon will not start when it is really cold and damp. What could be causing this problem?
--S.R.U.
Q: My wife’s 1993 Mercedes-Benz 190E sputters and dies, especially in cold and rain. Do you have any idea what would cause this problem?
--R.C.
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A: Cold, wet weather, which will be here in Southern California in a few months, is a challenge to the electrical systems of most automobiles. Fortunately, newer ignition systems are more resistant than ever to the problems caused by cold and humidity.
Traditional ignition systems would have a single coil to create a spark and a distributor to time that spark for each cylinder. Humidity could cause big problems when it penetrates into the distributor cap or into the high-voltage ignition wires that go to the spark plugs.
The best bet is to replace the distributor cap, make sure that all wiring is intact and not worn, and as a last resort, store the car indoors when it is not running.
But in newer systems that have a coil for each cylinder and computerized spark control instead of a distributor, rainy days are much less of a problem.
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Ralph Vartabedian cannot answer mail personally but responds in this column to automotive questions of general interest. Please do not telephone. Write to Your Wheels, Business Section, Los Angeles Times, 202 W. 1st St., Los Angeles, CA 90012. E-mail: ralph.vartabedian@latimes.com.
