Page 262 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

Newer ignition coil types do tend to be more durable even while providing almost double the voltage than older
conventional distributor types to feed power-hungry spark plugs. Coil blocks, pencil coils, and rail systems fall into
this category. They’re typically more efficient too, with no voltage lost in plug wires.
The downside to this is that once the coil goes bad, you’ll be replacing the whole part, or in the case of rail
systems, the whole rail. While the job is relatively straightforward and completed within minutes, car owners do
have to dig deep to get replacements. Prices vary for different engines and from different makers but are generally
higher the bigger (higher cylinder count) and more powerful the engine is.
The good news for older cars with distributor coils is that parts are significantly cheaper, and only the faulty parts,
either the distributors, the distributor cap, housing, or rotor, and (one or all) plug leads need to be changed. The
downside is that you’ll be doing this more often, as older ignition systems lose puff around the 30-thousand-mile
mark.
Spark Plug Issues

Plugs, unlike coil packs, need to be replaced at recommended intervals. After all, they provide the spark needed
for combustion. Here lifespans differ according to the plug type. The cheapest, basic copper and nickel plugs
should give you 30 thousand miles of worry-free motoring. Platinum variants last around 50, and the priciest
Iridium spark plugs are good for roughly 75 thousand miles.

Common problems are worn electrodes due to overheating, improper electrode gaps (meaning uneven sparks or
misfires), and cracked or damaged insulation housings. Contamination from oil (often from blown gaskets or worn
piston rings) or the electrodes collecting unburnt fuel and soot (carbonization) are other frequent reasons why
they fail prematurely. Plugs will also malfunction due to faulty coil packs supplying too high voltage.
Issues with Sensors

Ignition timing in newer engines is made easier with sensors. The crank position sensor for instance determines
the speed and position of the crankshaft so that coils and plugs can fire at the correct time. A faulty sensor often
leads to stalling and hard starts. Damaged or disconnected wiring is often the cause, but there can also be

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CITS : Automotive - Mechanic Diesel - Lesson 76 - 79