Page 263 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

problems with the internal sensor circuitry, damage to the plastic housing because of excessive engine heat, and
misaligned parts (wheel and pins) by which the sensor gauges the crank position.
The camshaft position sensor also has a say in the engine running smoothly, particularly the ignition system. This
part determines the position of the inlet and outlet valves in relation to the crankshaft and pistons, so helps the
ECU with correct timing and the firing sequence in the cylinders. Cam position sensors fail because of cracks in
the outer housing, exposure to moisture or dirt, more severe mechanical damage, or faulty wiring and connectors.
This leads to misfires, and stalling, and eventually, the car won’t start.
Troubleshooting Defective Ignition System Parts

While replacement parts are the easiest way out, most issues can be revealed with a simple diagnostics test.
Scanners with current software will generally point to the cylinder where misfires (or non-starts) occur, meaning
either bad plugs, defective coils, or wiring problems. Remove the spark plugs from wires or the coil-on-plug
connectors, remove the plugs with a socket, and do a thorough inspection. Plugs with cracked or damaged
insulation casings need to be replaced.
Those that have oil or carbon buildup can be cleaned using medium grit sandpaper or a wire brush. Once
cleaned, check the gap between electrodes with a gap tool. Plugs should also be tested with a spark plug testing
tool. This connects to the ignition wire on one end and the plug on the other, with the engine on and observing
whether there’s a visible spark. Lastly, check the wiring for plugs that connect them to coils as these are often the
first to cause ignition issues if damaged, frayed, or affected by environmental factors, such as moisture.
Coils and coil packs are generally tested with a multimeter and the resistance results are compared to
manufacturers’ recommendations (usually between 0.3 and 1 ohm). Distributors, distributor caps, and rotors are
first checked for visible damage, and then a multimeter is used to verify that resistance is up to scratch. The same
tool can be used to diagnose ignition modules.
Lastly, sensors are checked for rust, debris, loose wiring, or burned and broken connectors. Sensors will display
code readouts during diagnostic scans and a multimeter can verify if they are in working order.

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CITS : Automotive - Mechanic Diesel - Lesson 76 - 79