New cars, old mechanics
Modern vehicles are highly complex, and despite training sessions run by the industry, few mechanics manage to stay up to date. Jake Venter reports.
There was a time when the average farmer could get a reluctant engine to start by using one or two basic tricks.
If churning the starter didn’t bring joy, a reluctant vehicle could often be coaxed to life with a push. If that didn’t help, the next step was to remove the air-cleaner to see if the carburettor’s throat was wet, then pull off a spark plug lead while the starter rotated the engine to see if there was a spark.
Only if these methods failed would a mechanic be called in. The latter would repeat the above procedures before bringing the tools out. Those days are long gone. You cannot check on fuel reaching the engine in a fuel-injected engine, and if you check for a spark in the way mentioned, the high-voltage electronic ignition circuit may well suffer a voltage spike that could damage the engine control unit (ECU).
Using the starter motor for a long period or pushing the car for more than a few paces would most likely result in raw fuel reaching the catalytic converter (CAT). When the engine finally starts, this could see the CAT overheating and self-destructing.
Employing jumper leads is so risky that the Bosch handbook states that they should be used only in a real emergency.
Many people, even some mechanics, are unaware of these restrictions to time-honoured procedures, as well as many other new developments. The retail motor industry and major motor and component manufacturers organise regular talks and training sessions to correct any bad habits. I’ve attended some of these and often found them poorly attended.
One of the problems is the fact that many older mechanics think they are sufficiently experienced and informed. Another is that very few mechanics are true automotive enthusiasts.
For many years, I organised a Mechanic of the Year competition for a national magazine. There were separate categories for amateurs and qualified mechanics, and I invariably found that the amateurs knew more about ‘automotive theory’ than the mechanics!
TODAY, MANY WORKSHOPS USE DIAGNOSTIC CONSULTANTS
Fault-tracing on today’s cars is such a complicated procedure that many workshops employ specialist diagnostic consultants to detect any electronic misdemeanour. They use a laptop computer and/or a code reader, and the model-specific settings and procedures are a few seconds away on the Internet.
So let’s look at all the new components and ideas that an old, retired mechanic has not seen: • The ECU controls all the engine functions and operates on a very low 0,015 amp current. As noted, it can be damaged by a voltage spike or even by a damaged HT lead.
• The CAT can easily be damaged not only when excess fuel gets inside, but when a compression test is carried out without first deactivating the fuel pump relay.
• The knock sensor warns the ECU when the combustion is irregular so that the ignition timing can be retarded. The sensor is very fragile and can easily be damaged if dropped during replacement.
• The lambda sensor measures the oxygen level in the exhaust pipe and transmits a signal to the ECU. This then computes how much fuel to supply for the next combustion event. The sensor can be damaged by excessive heat, carbon build-up, or even chemicals in the anti-freeze if this leaks into the combustion chamber via a blown cylinder-head gasket. • Finally, torque-to-yield bolts are still relatively unknown, especially among the backyard brigade. The specifications for these require a low torque plus an angle through which the wrench has to be rotated to achieve the correct torque. This will ensure a high clamping force but cause the bolt to stretch permanently so that it cannot be re-used.
• Jake Venter is a journalist and a retired engineer and mathematician. Email him at jacobven[email protected] Subject line: Motoring.
ABOVE: As vehicles and their components become ever more sophisticated, mechanics find it increasingly challenging to keep abreast of new technology. It also means that tracing and repairing faults is risky, as damage can easily occur unless the mechanic knows exactly what to do.