Page 251 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

Importance of checking and setting correct ignition timing

Objectives: At the end of this lesson you shall be able to
• explain Importance of checking and setting correct ignition timing.

Ignition: The ignition system is a crucial component in internal combustion engines that generates and delivers
high-voltage electrical sparks to ignite the air-fuel mixture in the engine’s cylinders. It typically consists of a
battery, ignition coil, distributor (or ignition module), spark plugs, and related wiring. When the ignition system
fires, it initiates the combustion process, allowing the engine to generate power and operate.
Ignition timing: Idling, deceleration and running rich with closed throttle are some engine operating conditions
which produce excessive unburnt hydrocarbons and carbon monoxide in exhaust. The emission quality is greatly
affected by the ignition timing as shown in Fig.

Typical distributor advance curve for lower HC and CO exhaust emission.
Retarding ignition timing at idle tends to reduce exhaust emission in two ways. With retarded timing, exhaust
gas temperatures are higher (fuel economy is adversely affected), thereby promoting additional burning of the
hydrocarbons in the exhaust manifold. Since engine efficiency is reduced, retarded timing requires a slightly
larger throttle opening to maintain the same idle speed. The larger throttle opening means the possibility of better
mixing and combustion during idling. This reduces exhaust emissions appreciably especially during deceleration.
1 Engine Performance: Proper ignition timing ensures that the air-fuel mixture ignites at the optimal moment in
the engine’s cycle, maximizing power output and efficiency.
2 Fuel Efficiency: Correct timing results in more efficient combustion, leading to better fuel economy and
reduced fuel consumption.

3 Engine Longevity: Incorrect timing can cause engine knocking, which can lead to damage over time. By
setting the timing correctly, you prevent premature wear and tear on engine components.
4 Emissions Control: Proper timing helps minimize harmful emissions by ensuring that fuel is burned efficiently,
reducing the release of pollutants into the atmosphere.
5 Smooth Operation: When ignition timing is accurate, the engine runs smoothly with minimal vibration and
noise, enhancing overall vehicle performance and driving experience.

6 Locate Timing Marks: Find the timing marks on the engine’s crankshaft pulley or flywheel and the timing
scale on the engine block or timing cover. These marks indicate the top dead center (TDC) position of the
piston.
7 Consult Specifications: Refer to the manufacturer’s specifications for the correct ignition timing for your
vehicle. This information can usually be found in the owner’s manual or a repair manual.

8 Prepare Engine: Ensure the engine is at operating temperature and that all accessories are turned off. Disable
any advance mechanisms, such as vacuum advance or electronic advance, if applicable.
9 Connect Timing Light: Connect a timing light to the battery and the number one spark plug wire. Secure the
light so you can see the timing marks while the engine is running.

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CITS : Automotive - Mechanic Diesel - Lesson 71 - 75