When searching for the cause of any problem, the first step is deciding where to start looking. Sometimes it's obvious, but other times it takes a little detective work. A car owner who makes half a dozen different adjustments or replacements may be successful in fixing the problem (or its symptom), but he will not gain any experience in case the fault occurs again, and it is quite possible that he will spend more time and money than is really necessary. When thinking about the future, a calm and logical approach is more appropriate. Always take into account all signs of a possible malfunction or abnormality that were noticed before the problem occurred: loss of power, low or high instrument readings, unusual odors, etc. And remember that faulty components such as fuses or spark plugs may only be signs of another cause.
Below is a handy quick reference guide to the most common problems that may arise while operating your vehicle. These malfunctions and their possible causes are grouped by component or system under appropriate headings, such as "Engine," "Cooling System," etc. The chapter and/or section in which each malfunction is addressed is also indicated in parentheses. Whatever the fault, there are some basic principles to keep in mind below.
Is there a malfunction?. This simply means that before you begin work, you must be sure that the fault is present and know its symptoms. This is especially important if you are helping someone find a problem and they have not described it to you very accurately.
Don't ignore the obvious. For example, if the engine won't start, check if there's gas in the tank. Don't take anyone's word for it, and don't rely on the fuel gauge! If there's an electrical problem, first check for loose or broken wires.
Treat the disease, not the symptom. Replacing a dead battery with a charged one will save you from aggravated shoulders, but if the cause is not found, the same thing will happen with the new battery. Likewise, replacing oily spark plugs with a new set will get you driving again, but remember that the reason for the oiling is (if it wasn't just the wrong choice of spark plug type) we will have to wait for it to be identified and corrected.
Don't take anything on faith. In particular, do not forget that a "new" element may be defective (especially if it's been lying in the trunk for months), and do not exclude items from the chain of diagnostics of the cause of a malfunction just because they are new or recently installed. When you finally pinpoint the cause of a difficult-to-find problem, you'll likely realize that all the symptoms were there all along.