Bobcat Glow Plugs: Function, Troubleshooting, and Maintenance

[MikePhua]

Bobcat skid steers, like many other diesel-powered machines, rely on a range of components to ensure smooth operation, especially in colder weather. Among these components, glow plugs play a vital role in starting the engine under challenging conditions. This article explores the function of glow plugs in Bobcat machines, common issues, troubleshooting tips, and the steps to maintain or replace them, ensuring your equipment starts reliably, even during the harshest seasons.
What Are Glow Plugs?
Glow plugs are heating elements used in diesel engines to aid in the ignition of the fuel mixture. Diesel engines require a higher temperature to ignite the air-fuel mixture compared to gasoline engines, especially during cold starts. The role of glow plugs is to pre-heat the combustion chamber, raising the temperature to a level that allows for efficient fuel ignition. This is especially important in colder temperatures, where a cold engine may fail to start without the aid of glow plugs.
How Do Glow Plugs Work?
When you turn the key to start your Bobcat machine, the glow plugs are activated by the engine control system. They heat up rapidly and warm the combustion chamber. Once the engine reaches a sufficient temperature, the glow plugs automatically turn off, and the engine should start normally. The glow plug system operates for a few seconds after the ignition is engaged, and its effectiveness is directly linked to the starting performance of the engine.
Glow Plug Failure Signs
Over time, glow plugs can wear out or become damaged. This is common, especially in machines that are subjected to heavy use or harsh weather conditions. Here are some signs that your Bobcat’s glow plugs might be failing:

1. Hard Starts in Cold Weather
   If the machine starts with difficulty or requires multiple attempts, especially during colder weather, it could be due to a malfunctioning glow plug system. Diesel engines are sensitive to low temperatures, and without proper heating, the engine struggles to fire.
   
2. Rough Idle or Engine Misfire
   A faulty glow plug can result in incomplete combustion, leading to rough idling, poor fuel efficiency, and engine misfire during startup.
   
3. Check Engine Light or Warning Indicators
   Many Bobcat models have a diagnostic system that will display a warning light if there’s a glow plug issue. A glowing check engine light or a specific glow plug warning might indicate that one or more of the glow plugs have failed.
   
4. Excessive White Smoke from Exhaust
   If a glow plug is not functioning properly, the engine may emit white smoke during startup. This is caused by the incomplete combustion of fuel in the engine’s cylinders.
   

Troubleshooting Glow Plug Issues
If you notice any of the symptoms above, it’s time to troubleshoot the glow plug system. Here are some steps to help you identify the issue:

1. Test the Glow Plugs
   Using a multimeter, check the resistance of each glow plug. A healthy glow plug will have a resistance typically between 0.5 to 2 ohms. If a glow plug has a reading that’s much higher or shows an open circuit (infinite resistance), it’s faulty and needs to be replaced.
   
2. Inspect the Glow Plug Relay
   The relay controls the operation of the glow plugs. If the relay malfunctions, it could prevent the glow plugs from receiving power. Check the relay for continuity using a multimeter, and replace it if necessary.
   
3. Check the Wiring and Connections
   Inspect the wiring and connections to the glow plugs. Look for any corrosion, loose connections, or signs of wear that could prevent the plugs from receiving power.
   
4. Test the Fuse
   The glow plug system is often protected by a fuse. If the fuse is blown, the system won’t work. Check the fuse associated with the glow plugs and replace it if necessary.
   

Replacing Bobcat Glow Plugs
If you’ve determined that the glow plugs are faulty, replacing them is essential to restore your machine’s starting performance. Here’s how to replace glow plugs on a Bobcat:

1. Prepare the Machine
   Ensure the machine is turned off and the battery is disconnected before working on the electrical system. Allow the engine to cool if it has been running recently.
   
2. Locate the Glow Plugs
   On most Bobcat models, the glow plugs are located on the cylinder head. They are typically arranged in a row along the top of the engine, near the injectors.
   
3. Remove the Glow Plugs
   Using the appropriate socket wrench, carefully remove each glow plug. Take your time to avoid damaging the surrounding components. If a glow plug is stuck, apply a penetrating oil and allow it to sit for a few minutes before attempting again.
   
4. Install the New Glow Plugs
   Install the new glow plugs in the same position as the old ones. Tighten them with a torque wrench to the manufacturer’s recommended specifications to ensure a proper seal.
   
5. Reconnect the Wiring and Battery
   Once the new plugs are installed, reconnect the electrical connections to each glow plug. Ensure all wiring is secure and free of corrosion. Finally, reconnect the battery.
   
6. Test the System
   Turn on the ignition and let the glow plug system warm up. The machine should start with no issues. If the problem persists, double-check the relay, wiring, and fuse.
   

Glow Plug Maintenance Tips
Proper maintenance can extend the lifespan of your glow plugs and reduce the likelihood of failure. Here are some tips for maintaining your Bobcat’s glow plug system:

1. Regular Inspection
   Regularly inspect the glow plug system during routine maintenance. Look for signs of wear or damage on the plugs, wiring, and relays.
   
2. Use Quality Fuel
   Poor-quality fuel can cause carbon buildup on the glow plugs, which can impair their performance. Always use clean, high-quality diesel fuel to reduce wear on the glow plug system.
   
3. Avoid Short Starting Cycles
   When starting the engine, avoid rapidly turning the ignition on and off. Allow the glow plugs to heat the combustion chamber fully before starting. This ensures that the engine gets the proper pre-heat, improving the lifespan of the plugs.
   
4. Store the Equipment Properly
   If the Bobcat is stored in extremely cold conditions, consider using a block heater or another auxiliary heating system. This reduces the load on the glow plugs during startup and makes starting easier in colder weather.
   

Conclusion
Glow plugs are an essential component in Bobcat machines, ensuring reliable starts, particularly in colder climates. Regular maintenance, proper troubleshooting, and timely replacement of faulty glow plugs will keep your Bobcat equipment running smoothly. By following these guidelines, operators can avoid costly repairs, reduce downtime, and extend the life of their machinery. Whether you’re using the equipment for construction, landscaping, or other heavy-duty applications, ensuring your glow plugs are in good condition is crucial for optimal performance.