NMA Email Newsletter: Issue #47

Uncommon Auto Service Advice

Members of the NMA have free web access to the technical services of MOTOR WATCH, just log in to the members only section and click the MOTOR WATCH link. MOTOR WATCH also provides a quarterly newsletter, print and electronic, to it’s subscribers. NMA members can access the electronic version.

The most recent MOTORWATCH newsletter had some service tips and answers to questions that you aren’t likely to find in automotive magazines or your owner’s manual. Here’s a few examples:

Virtually all automobiles are equipped with 12 volt batteries. When checking the charge on these batteries the meter will read 12.6 volts, for a fully charged battery. Logic would suggest that a battery that is only half charged would read 6.3 volts. Logic fails us in this situation as a half charged battery will read 12.3 volts; not a whole lot of difference between a full charge and a half charge, 0.3 volts!

Speaking of batteries; as most of us have unfortunately experienced, when a conventional wet cell battery fails it can happen “right now.” However, the new style Absorbed Glass Mat batteries die in a more predictable fashion; at the end of their usable life they begin to slowly lose their power. Typically, you should have adequate forewarning, as indicated by reduced starting power, to replace your battery before you find yourself dead in the water in an abandoned shopping center parking lot.

Common folklore has it that accumulated sludge and debris in the gas tank can damage fuel pumps. Now, because fuel pumps are located in the fuel tank, a failed unit can be a very pricey repair. The preventative medicine is to not allow your fuel tank to get so low that the fuel pump will engorge itself and ruin its innards. This is a case of good advice, but for the wrong reason. First, modern fuels have very little contaminants. Second, there is a filter that screens out most of the contaminants and those that do go through will not harm the pump. However, letting the pump run dry, i.e. running out of fuel, can damage the pump because the fuel is its source of coolant. So, the advice still has merit, just for a different reason.

One last tip; most folks know that when replacing burned out headlights that they should not touch the glass part of the bulb with bare fingers as the finger prints can significantly shorten the bulb’s life. However, not many of us backyard mechanics know that the same warning applies to modern sparkplugs! Greasy finger prints on the plug porcelain insulators can eventually result in a misfiring sparkplug, which can also damage other ignition components.

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