Troubleshooting Bobcat 773G that Won't Stay Running

[MikePhua]

The Bobcat 773G is a versatile and reliable skid steer loader commonly used for construction, landscaping, and various material handling tasks. However, like any piece of heavy equipment, it can experience mechanical issues. One of the more frustrating problems operators may encounter is the machine running briefly and then stalling or failing to stay on. This issue can have multiple causes, ranging from fuel system problems to electrical malfunctions. In this article, we will explore potential causes for this issue and provide troubleshooting tips to help resolve it.
Understanding the Bobcat 773G
The Bobcat 773G, part of the G-Series of skid steer loaders, was designed for versatility, efficiency, and ease of use. It is powered by a 67 horsepower, turbocharged diesel engine and has a lifting capacity of up to 1,700 pounds (771 kg), making it a solid choice for a variety of tasks. The 773G also comes equipped with advanced hydraulic systems and various attachments that can be used in construction, material handling, and site preparation.
Common Symptoms and Diagnosis
When a Bobcat 773G experiences issues with staying running, the problem can manifest in several ways:

1. Engine Stalls After Starting: The engine may start but quickly shut down after running for a few seconds.
   
2. Intermittent Running: The machine may run for a few minutes and then suddenly lose power and stall.
   
3. Rough Idle: The engine may idle unevenly before shutting off.
   

The root causes of these issues are often related to fuel delivery, electrical components, or engine management. Here’s a breakdown of possible causes:
1. Fuel System Issues
One of the most common reasons a skid steer like the Bobcat 773G won’t stay running is a problem with the fuel system. If the engine is not getting the correct fuel flow, it will start but fail to continue running.

• Clogged Fuel Filters: Over time, fuel filters can become clogged with dirt, debris, and sediment, restricting the fuel flow to the engine. A clogged fuel filter can prevent the engine from receiving enough fuel to maintain operation.
  
• Air in the Fuel Line: If air enters the fuel system, it can cause the engine to stall. This often occurs after the fuel tank has run low or after a fuel filter change. Air bubbles in the line can prevent the proper fuel delivery to the engine, causing it to sputter or stall.
  
• Fuel Pump Failure: The fuel pump is responsible for delivering fuel from the tank to the engine. If the fuel pump is malfunctioning or weak, it can lead to insufficient fuel delivery, causing the engine to run intermittently or stall.
  
• Contaminated Fuel: Water or dirt in the fuel tank can clog the fuel injectors or filter and disrupt the engine’s operation. If the fuel is contaminated, it can cause the engine to fail to run properly.
  

Troubleshooting Fuel System Issues:

• Check and replace the fuel filter if necessary.
  
• Bleed the fuel system to remove any air trapped in the fuel lines.
  
• Inspect the fuel tank for any contaminants and clean it out if necessary.
  
• Test the fuel pump to ensure it is delivering the correct pressure to the injectors.
  

2. Electrical System Problems
Another potential cause for the engine failing to stay on could be related to the electrical system. A weak or failing electrical component can cause the engine to stall.

• Battery and Charging System: A low or faulty battery can cause the engine to start but quickly lose power. The alternator may not be charging the battery properly, leaving the system without sufficient electrical power to keep the engine running.
  
• Faulty Wiring or Connections: Loose or corroded wiring connections can cause intermittent electrical issues, resulting in the engine stalling. Pay close attention to the wiring connected to the ignition system, the fuel system, and sensors.
  
• Ignition Switch Issues: A malfunctioning ignition switch can cause the engine to start but then cut power shortly afterward. Ensure the ignition switch is working properly and is not short-circuiting.
  
• ECM (Engine Control Module) Failure: The ECM controls the engine’s fuel injection, timing, and other vital functions. A failing ECM could cause the engine to shut off unexpectedly.
  

Troubleshooting Electrical System Issues:

• Test the battery voltage and charging system. A voltage test can determine if the battery is properly charged and if the alternator is providing adequate power.
  
• Inspect all wiring for signs of corrosion, wear, or loose connections.
  
• Check the ignition switch for any faults.
  
• Use a diagnostic scanner to check for fault codes related to the ECM.
  

3. Air Intake or Exhaust Issues
A problem with the air intake or exhaust system can also cause the engine to stall. If the engine is not receiving the proper airflow or if the exhaust system is restricted, it can affect performance.

• Clogged Air Filter: A clogged air filter will restrict airflow to the engine, causing it to run rich or stall due to insufficient oxygen.
  
• Exhaust Blockage: A blocked exhaust system can cause a buildup of pressure in the engine, leading to stalling. This could be due to a clogged muffler or catalytic converter.
  

Troubleshooting Air Intake and Exhaust Issues:

• Inspect and replace the air filter if necessary.
  
• Check the exhaust system for blockages or excessive soot buildup, and clean as needed.
  

4. Fuel Injector Problems
Fuel injectors are responsible for delivering fuel into the combustion chamber. If one or more injectors fail, it can cause poor engine performance, stalling, or even complete engine failure.

• Clogged or Dirty Injectors: Over time, injectors can become clogged with carbon deposits or dirt, affecting their performance.
  
• Injector Failure: If the injectors themselves are faulty, the engine may fail to run correctly or stall altogether.
  

Troubleshooting Injector Problems:

• Perform a fuel injector cleaning or replacement if necessary.
  
• Inspect the injector nozzles for signs of clogging or wear.
  

5. Engine Overheating or Low Oil Pressure
Another cause of stalling can be an engine that is overheating or has low oil pressure. When the engine’s internal components do not receive sufficient lubrication, or if the engine temperature rises too high, it can lead to stalling or shutdowns.

• Low Oil Pressure: A drop in oil pressure can cause the engine to shut down to prevent damage. This could be due to low oil levels, a malfunctioning oil pump, or a clogged oil filter.
  
• Engine Overheating: If the engine is running too hot, it can automatically shut down as a protective measure. Overheating can be caused by a malfunctioning cooling system, low coolant levels, or a blocked radiator.
  

Troubleshooting Oil Pressure and Overheating Issues:

• Check the oil level and ensure that the oil is clean and at the proper level.
  
• Inspect the oil pump and filter for any issues.
  
• Ensure the cooling system is working properly by checking coolant levels and inspecting the radiator for blockages.
  

Conclusion
When a Bobcat 773G fails to stay running, the issue could be caused by several factors, from fuel system malfunctions to electrical or mechanical problems. By carefully diagnosing each potential issue, operators can identify and address the root cause of the problem. It’s important to check the fuel system, electrical components, air intake, exhaust system, and ensure proper engine lubrication to prevent stalling. Regular maintenance and timely repairs can help keep the Bobcat 773G running smoothly for years, ensuring that it remains a reliable and valuable tool on the job site.