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Fuel, Spark & Compression

GenSpring Power • May 22, 2015

In our earlier post, How Long Can My Generator Run? , we discussed the role of fuel and oil to keep your generator running during an extended outage.   In this post we will discuss how fuel, spark & compression work together to allow your engine to start and continue to run so that your home generator can produce power when you need it.

The engine is the heart of your generator system. Without the mechanical energy produced by the internal combustion engine, no electric power will be generated.   For the engine to start and run, sufficient rotation must occur.

Cranking, initiated by the control board of the generator system, is the action that occurs when the starter causes the engine to rotate or turn over.   The starter is an electric DC motor that facilitates the cranking process. The starter receives its power from the battery, via a starter contactor or solenoid.   Therefore the battery is a critical component of the cranking process and must have sufficient amp hour capacity to turn the engine over.

Starting and running is the desired end result that occurs when sufficient revolutions of the engine occur to cause compression and spark to combine with the correct mixture of fuel and air to allow combustion in the cylinders. Once the engine has started, it will continue to run as long as sufficient fuel, spark and compression is present.

Fuel as the name implies, is the energy that allows the engine to run.   Fuel needs to mix with the proper amount of air for combustion.   Air is drawn through a filter to remove undesirable impurities.   The air filter acts as a cleaner and measurement device to ensure the correct fuel air ratio.   Therefore a clean air filter plays a critical role in ensuring the right balance of fuel and air.

Spark is achieved through induction to the spark plugs from the magnetos as the flywheel rotates during starting and running.   Spark plugs are specific to the engine application and the work it is intended to do.   Weak or no spark can be traced to three potential issues – bad magnetos, cracked spark plug wires causing the spark to ground out, or fouled spark plugs.

Compression is achieved through the movement of the pistons within the cylinders. This movement, when combined with sufficient force, allows the pistons to create adequate compression with the fuel and air mix to support combustion.   Valves within the cylinder head open and close as the piston moves up and down, allowing fuel to enter the combustion chamber and the exhaust to exit at the optimum time.   It is not uncommon for the compression to be slightly different between two cylinders, however, if the differential is more that 25%, then either the valves are out of adjustment or there is a more serious problem within one of the cylinders.

Always consult the Manufacturer’s Operation and Owner Manuals for precise information relative to your home generator system.   This overview is not intended or replace competent technical service. Proper maintenance, whether you do it yourself or have someone do it for you, pays for itself through performance, longer equipment life and lower overall cost.   Always use genuine parts.   They are specifically designed for your engine and will help ensure the best performance.

GenSpring Power offers scheduled maintenance plans to help our customers keep their generator engines in top operating condition. With over 750 service customers, there isn’t much we haven’t seen.   Visit our Generator Maintenance page under the Services tab for more information.   If you are interested in maintenance kits, please visit our online Parts store – www.genspring-parts.com .

At GenSpring Power, Power You Can Depend On is not just a slogan, it’s a commitment!

Copyright GenSpring Power 2015. GenSpring Power is a registered trademark of GenSpring Power Inc.

Clayton Preble

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