Jaguar Fault Finding

With any fault-finding, the first step is to decide where to begin investigations.

Sometimes this is obvious, but on other occasions, a little detective work will be necessary. The owner who makes half a dozen haphazard adjustments or replacements may be successful in curing a fault (or its symptoms), but will be none the wiser if the fault recurs, and ultimately may have spent more time and money than was necessary. A calm and logical approach will be found to be more satisfactory in the long run. Always take into account any warning signs or abnormalities that may have been noticed in the period preceding the fault - power loss, high or low gauge readings, unusual smells, etc - and remember that failure of components such as fuses or spark plugs may only be pointers to some underlying fault.

Whatever the fault, certain basic principles apply. These are as follows:

Verify the fault. This is simply a matter of being sure that you know what the symptoms are before starting work. This is particularly important if you are investigating a fault for someone else, who may not have described it very accurately.

Don’t overlook the obvious. For example, if the vehicle won’t start, is there fuel in the tank? (Don’t take anyone else’s word on this particular point, and don’t trust the fuel gauge either!) If an electrical fault is indicated, look for loose or broken wires before digging out the test gear.

Cure the disease, not the symptom. Substituting a flat battery with a fully-charged one will get you off the hard shoulder, but if the underlying cause is not attended to, the new battery will go the same way. Similarly, changing oil-fouled spark plugs for a new set will get you moving again, but remember that the reason for the fouling (if it wasn’t simply an incorrect grade of plug) will have to be established and corrected.

Don’t take anything for granted. Particularly, don’t forget that a “new” component may itself be defective (especially if it’s been rattling around in the boot for months), and don’t leave components out of a fault diagnosis sequence just because they are new or recently-fitted. When you do finally diagnose a difficult fault, you’ll probably realize that all the evidence was there from the start.

For any problems large or small or for any general advice, contact Jagtech for assistance.