Engine Starters Information
Last revised: October 17, 2024
Reviewed by: Scott Orlosky, consulting engineer
Engine starters provide the initial rotation for internal combustion engines. They cause the power train components (pistons, fuel system, crankshaft) to move before ignition, enabling the engine to turn over so that it can then operate under its own power.
Engine starters are available for engines of all sizes, and include products other than just electric motors.
Applications
Engine starters are used in many applications including:
- Gasoline, marine, and diesel engines
- Portable generators
- Mining equipment
- Construction equipment
- Irrigation pumps
- Turbines
- Jet engines
- Aircraft
Types
Engine starter types include:
Pneumatic
Pneumatic engine starters or air starters are used to start diesel engines, gas turbines, and some reciprocating engines. They provide rapid acceleration and high turning speeds for immediate ignition. Compared to electric starters, air starters and air start systems have a higher power-to-weight ratio. Typically, they admit compressed air or gas to cylinders whose pistons are just over top dead center, forcing them downward. The compressed air source can be a dedicated starter tank co-located with the engine, or can be sourced from shop air, provided it meets the minimum volume and pressure requirements.
Specifications for pneumatic air starters include:
- Maximum working pressure
- Maximum power
- Speed at maximum power
- Maximum torque
- Net weight
- Maximum diameter of the air feed piping
Hydraulic
Hydraulic engine starters are used in field generators, marine propulsion engines, water pumping equipment for fire suppression, and hydraulic fracturing (fracking) equipment for oil and gas exploration. They are also used in diesel engines, typically those with six to 16 cylinders that require emergency starts over a range of temperatures.
Like pneumatic engine starters and other air starting systems, hydraulic engines starters are designed for spark-less operation. Related components include valves, pumps, filters, reservoirs, and piston accumulators.
Product specifications for hydraulic engine starters include pressure range, volume flow rate, and crank size.
Electric
Electric engine starters use either a permanent magnet or a direct current (DC) electric motor with a starter solenoid. They are often used in cars, trucks, boats, and construction equipment. When a key-operated switch is activated, current from a battery is applied to the solenoid. The solenoid then engages a drive pinion, pushing the drive pinion until it meshes with the starter ring gear on the engine’s flywheel. Once the engine starts, a spring separates the pinion gear from the ring gear, causing the starter motor to stop.
Specifications for electric engine starters include parameters for connecting and switching.
Spring
Spring starters are mechanical devices that do not require electricity, hydraulic pressure, or compressed air. Energy is stored in a manually-rechargeable power spring or spring pack that eliminates the need for a battery, alternator, or wiring. In some systems, a conversion kit can be installed to provide electrical power.
Typically, spring starters are used in industrial, marine and agricultural applications, often in remote or hazardous locations. Where electricity is not readily available or risk of sparking is dangerous.
Manual and Recoil
Manual engine starters and recoil engine starters are used in small horsepower devices like lawnmowers, snow blowers, motorcycles, chainsaws, and other small engines. They work similarly to electric starters, except muscle power is substituted in place of electrical power. The starter mechanism is spring loaded so that the starter rope or cable will retract into the starter mechanism as they often take a few pulls on the cable before the engine ignition take place.
Standards
A-A-59294 — Starters, engine, electrical
MIL-S-22999 — Starters, aircraft engine, hydraulic
Engine Starter FAQs
Why is a starter necessary for DC motors in certain applications?
DC motors have a high starting torque, which requires high startup currents. To reduce these high startup currents to a safe level, a starter is added in series with the armature winding to add resistance and limit the current.
What are the advantages and disadvantages of electric starters compared to hydraulic or pneumatic types?
These are the advantages and disadvantages of electric starters compared to other types of engine starters:
Advantages of Electric Starters
Electric starters are generally easy to operate. They typically require just the push of a button or turn of a key to start the engine.
Electric starters are highly reliable and have fewer moving parts compared to hydraulic or pneumatic starters, which can reduce the likelihood of mechanical failure.
They require less maintenance compared to hydraulic and pneumatic starters, which may need regular checks for leaks or pressure issues.
Electric starters are widely available and commonly used in a variety of applications, from small engines to large industrial engines.
They are generally more compact and lighter in weight compared to hydraulic and pneumatic starters, making them suitable for applications where space and weight are critical factors.
Disadvantages of Electric Starters
Electric starters rely on a battery for power. If the battery is weak or dead, the starter will not function, which can be a significant drawback in critical applications.
They require a high current draw from the battery, especially during startup. This can be a limitation in applications where battery capacity is limited or compromised.
Electric starters can be sensitive to extreme temperatures and environmental conditions, which may affect their performance and reliability.
While electric starters provide sufficient torque for many applications, they may not be suitable for very large engines that require extremely high starting torque, where hydraulic or pneumatic starters might be more appropriate.
Comparison with Other Types
Hydraulic Starters:
Advantages: Provide high torque, suitable for large engines, and can operate in extreme conditions.
Disadvantages: More complex, require regular maintenance, and are heavier.
Pneumatic Starters:
Advantages: High torque, reliable in harsh environments, and can be used in explosive atmospheres.
Disadvantages: Require a compressed air source, more complex, and need regular maintenance.
Cartridge Starters:
Though rarely used anymore, a cartridge starter is used to fire off a controlled explosion within the intake manifold of an engine, giving it enough “kick” that will initiate a sustaining cycle. These were widely used in the 1930s and 1940s to start up airplane engines and armored vehicles. They were also known as a “shotgun starter.”
Advantages: High reliability, can be used in remote locations without electrical power.
Disadvantages: Limited to specific applications, require replacement cartridges, and can be more expensive to operate.
How does an electric starter work in detail?
When the ignition key is turned or the start button is pressed, an electrical signal is sent to the starter solenoid.
The starter solenoid acts as a relay, receiving the electrical signal and closing the circuit between the battery and the starter motor. This allows current to flow from the battery to the starter motor.
The solenoid also pushes the starter gear (also known as the pinion gear) forward to engage with the engine's flywheel. The flywheel is a large gear attached to the engine's crankshaft.
The starter motor, which is a DC motor, begins to spin. This motor draws current from the battery to generate the necessary torque to turn the engine's crankshaft.
As the starter motor spins, it turns the starter gear, which in turn rotates the flywheel. The rotation of the flywheel causes the engine's crankshaft to turn.
The turning of the crankshaft initiates the engine's internal combustion process. Once the engine starts running on its own, the starter motor is no longer needed.
After the engine starts, the starter solenoid disengages the starter gear from the flywheel, and the starter motor stops running. This prevents the starter motor from being damaged by the running engine.
Key Components Involved
- Battery: Provides the electrical power needed to operate the starter motor.
- Starter Solenoid: Acts as a relay to control the flow of electrical current to the starter motor and engages the starter gear with the flywheel.
- Starter Motor: A DC motor that generates the torque needed to turn the engine's crankshaft.
- Starter Gear (Pinion Gear):Engages with the engine's flywheel to transmit the rotational force from the starter motor to the crankshaft.
- Flywheel: A large gear attached to the engine's crankshaft that is turned by the starter gear to initiate engine rotation.
Additional Considerations
High Current Draw: Electric starters require a high current draw from the battery, especially during startup. This is why a robust battery is essential for reliable operation.
Series Resistance: In some applications, a starter may include a series resistance to reduce high startup currents to a safe level, as mentioned in the context of DC motors.
What are the key considerations for maintaining hydraulic starters?
Key considerations for maintaining hydraulic starters include:
Regular Inspection:
Hydraulic Fluid Levels: Regularly check and maintain the hydraulic fluid levels to ensure the system operates efficiently.
Leak Detection: Inspect the system for any signs of leaks in the hydraulic lines, seals, and connections. Leaks can lead to a loss of pressure and reduced performance.
Component Wear and Tear:
Seals and Gaskets: Regularly inspect seals and gaskets for wear and replace them as needed to prevent leaks and maintain pressure.
Hydraulic Pump: Ensure the hydraulic pump is functioning correctly and replace it if it shows signs of wear or failure.
Pressure Checks:
System Pressure: Regularly check the system pressure to ensure it is within the specified range. Incorrect pressure can lead to inefficient operation or damage to the starter.
Pressure Relief Valves: Inspect and test pressure relief valves to ensure they are functioning correctly and set to the appropriate pressure levels.
Filter Maintenance:
Hydraulic Filters: Regularly replace hydraulic filters to prevent contaminants from entering the system and causing damage to components.
Environmental Factors:
Temperature Control: Ensure the hydraulic system is operating within the recommended temperature range. Extreme temperatures can affect the viscosity of the hydraulic fluid and the performance of the starter.
Contaminant Control: Keep the hydraulic system clean and free from contaminants such as dirt and moisture, which can affect performance and cause damage.
What are the common issues faced with hydraulic starters and how to troubleshoot them?
Here are the common issues faced with hydraulic starters and how to troubleshoot them:
Common issues and troubleshooting for hydraulic starters include:
Hydraulic Fluid Leaks
Issue: Leaks in the hydraulic lines, seals, or connections can lead to a loss of pressure and reduced performance.
Troubleshooting:
- Regularly inspect the hydraulic lines, seals, and connections for any signs of leaks.
- Replace worn or damaged seals and gaskets to prevent leaks.
- Ensure all connections are properly tightened and secure.
- Periodically check the ability of system to hold pressure.
Low Hydraulic Fluid Levels
Issue: Insufficient hydraulic fluid can cause the system to operate inefficiently or fail to start the engine.
Troubleshooting:
- Regularly check and maintain the hydraulic fluid levels.
- Refill the hydraulic fluid to the recommended levels as specified by the manufacturer.
Pressure Loss
Issue: Incorrect system pressure can lead to inefficient operation or damage to the starter.
Troubleshooting:
- Regularly check the system pressure to ensure it is within the specified range.
- Inspect and test pressure relief valves to ensure they are functioning correctly and set to the appropriate pressure levels.
- Address any leaks or component failures that may be causing pressure loss.
Component Wear and Tear
Issue: Wear and tear on components such as seals, gaskets, and the hydraulic pump can affect the performance of the starter.
Troubleshooting:
- Regularly inspect seals, gaskets, and the hydraulic pump for signs of wear and replace them as needed.
- Ensure the hydraulic pump is functioning correctly and replace it if it shows signs of wear or failure.
Contaminated Hydraulic Fluid
Issue: Contaminants such as dirt and moisture in the hydraulic fluid can cause damage to components and affect performance.
Troubleshooting:
- Regularly replace hydraulic filters to prevent contaminants from entering the system.
- Keep the hydraulic system clean and free from contaminants.
- Use high-quality hydraulic fluid and ensure it is stored properly to prevent contamination.
Temperature Extremes
Issue: Extreme temperatures can affect the viscosity of the hydraulic fluid and the performance of the starter.
Troubleshooting:
- Ensure the hydraulic system is operating within the recommended temperature range.
- Use hydraulic fluid that is suitable for the operating temperature conditions.
Maintaining hydraulic starters involves addressing common issues such as hydraulic fluid leaks, low fluid levels, pressure loss, component wear and tear, contaminated fluid, and temperature extremes. Regular inspection, maintenance, and adherence to relevant standards such as L-S-22999 for aircraft engine hydraulic starters are crucial for ensuring reliable and efficient operation
What are the advantages of using hydraulic starters in extreme conditions?
Hydraulic starters provide high torque, making them suitable for starting large engines that require significant force to initiate rotation. This high torque capability is particularly beneficial in extreme conditions where engines may be more difficult to start.
Hydraulic starters are known for their reliable operation in extreme conditions, such as very high or low temperatures. The hydraulic fluid used in these starters can be formulated to maintain its properties across a wide temperature range, ensuring consistent performance.
Hydraulic starters are built to withstand harsh environments. Their robust construction and fewer moving parts compared to other types of starters reduce the likelihood of mechanical failure, making them ideal for use in extreme conditions.
Hydraulic systems, if well-sealed and maintained, are less affected by environmental factors such as dust, moisture, and contaminants. This resistance to environmental conditions helps maintain the performance and reliability of the starter in extreme environments.
Engine Starter Media Gallery
References
GlobalSpec—Fundamentals of AC vs DC motors
GlobalSpec—How do induction motors work?
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