Lull 844 Engine Cycling Problems and Solutions

[MikePhua]

The Lull 844, a high-performance telehandler, is widely used in construction and industrial settings for its lifting capacity and versatile capabilities. However, like any heavy machinery, it can experience engine-related issues that affect its performance. One of the common problems reported by operators is "engine cycling," where the engine revs up and down erratically, causing operational inconsistencies and potential damage to the machine. This article will delve into the causes, symptoms, and troubleshooting steps for addressing engine cycling in the Lull 844.
Understanding Engine Cycling in Heavy Equipment
Engine cycling refers to the intermittent revving or surging of an engine, where the RPM (revolutions per minute) fluctuates, either increasing or decreasing without the operator's input. This behavior can result in a loss of power, rough idling, or erratic operation, making the equipment difficult to control.
In a telehandler like the Lull 844, which is designed for lifting, hoisting, and positioning heavy loads, engine cycling can be particularly problematic. The fluctuating engine speeds can make it harder to lift loads smoothly, adjust the boom, or navigate through work areas.
Common Causes of Engine Cycling in the Lull 844
Several factors can contribute to engine cycling in the Lull 844. Some of these causes are directly related to the engine's components, while others stem from external factors such as the fuel system or electronic controls.
1. Fuel System Issues
The fuel system plays a critical role in regulating engine performance. A common cause of engine cycling is a problem with the fuel delivery system. If the engine is not receiving a consistent fuel supply, it can result in fluctuating power output.
Possible Causes:

• Clogged fuel filters: Over time, dirt, debris, and contaminants can accumulate in the fuel filter, restricting fuel flow.
  
• Faulty fuel pump: A malfunctioning fuel pump may not supply enough fuel to maintain stable engine speed.
  
• Air in the fuel lines: Air trapped in the fuel lines can cause inconsistent fuel delivery, leading to engine cycling.
  

Solution:

• Replace clogged fuel filters and clean the fuel lines.
  
• Inspect the fuel pump for proper function and replace if necessary.
  
• Bleed the fuel system to remove any trapped air.
  

2. Electrical System Problems
The Lull 844's engine is controlled by an electronic control module (ECM) that manages the fuel injection, ignition, and other engine parameters. A malfunction in the ECM or its sensors can lead to improper engine performance, including erratic idling and engine cycling.
Possible Causes:

• Faulty sensors: Sensors that monitor temperature, pressure, or airflow may fail or send incorrect readings to the ECM, leading to fluctuations in engine speed.
  
• Wiring issues: Damaged or corroded wiring can disrupt the signal from the ECM to the engine, causing irregular engine performance.
  
• ECM failure: In rare cases, the ECM itself may malfunction, leading to poor engine control.
  

Solution:

• Inspect the electrical wiring for wear, corrosion, or loose connections.
  
• Test and replace faulty sensors, such as the throttle position sensor (TPS) or mass airflow sensor (MAF).
  
• In the case of an ECM failure, it may need to be reset or replaced.
  

3. Idle Speed Adjustment Problems
The idle speed control system regulates the engine's RPM when the telehandler is idling. If this system is misadjusted, it can cause the engine to cycle between high and low RPMs, leading to an erratic idle and poor performance.
Possible Causes:

• Misadjusted idle speed: The idle speed may be set too high or too low, causing fluctuations in engine speed.
  
• Faulty idle control valve: The idle control valve regulates the engine’s idle speed, and a malfunctioning valve can lead to cycling.
  

Solution:

• Adjust the idle speed using the manufacturer-recommended settings.
  
• Inspect the idle control valve for any faults and replace it if necessary.
  

4. Air Intake or Exhaust Restrictions
Restricted airflow into or out of the engine can cause a variety of performance issues, including engine cycling. The engine needs a constant supply of fresh air for combustion, and any restriction in the intake or exhaust system can interfere with this process.
Possible Causes:

• Clogged air filter: A dirty or clogged air filter can restrict the flow of air to the engine, leading to poor performance.
  
• Exhaust system blockages: A blockage in the exhaust system, such as a clogged catalytic converter or exhaust pipe, can cause back pressure and affect engine operation.
  

Solution:

• Replace or clean the air filter to ensure proper airflow.
  
• Inspect the exhaust system for any blockages and clear them as needed.
  

5. Hydraulic System Problems
The Lull 844 relies on hydraulic power to operate its boom and lift functions. If there are issues with the hydraulic system, they can indirectly affect the engine’s performance. Hydraulic problems can cause the engine to work harder than usual, leading to fluctuating RPM.
Possible Causes:

• Hydraulic fluid contamination: Contaminated hydraulic fluid can cause increased pressure within the hydraulic system, placing additional strain on the engine.
  
• Faulty hydraulic pump: A malfunctioning hydraulic pump may cause erratic performance, affecting the engine's load and speed.
  

Solution:

• Regularly change the hydraulic fluid and inspect the hydraulic filters for contamination.
  
• Test and replace the hydraulic pump if necessary.
  

Preventative Measures to Avoid Engine Cycling
To avoid engine cycling in the future, operators and maintenance personnel can take several preventative steps:

1. Regular Maintenance: Adhering to the manufacturer's recommended maintenance schedule for the engine, fuel system, electrical components, and hydraulic system is essential for preventing cycling issues.
   
2. Fuel System Care: Regularly check and replace fuel filters, clean the fuel lines, and ensure that the fuel pump is functioning correctly.
   
3. Electrical System Inspections: Periodically inspect the electrical wiring, connectors, and sensors to prevent any signal issues that could cause engine cycling.
   
4. Air Intake System: Keep the air filter clean and free from debris, and inspect the intake and exhaust systems for blockages that could hinder engine performance.
   

Conclusion
Engine cycling in the Lull 844 can be caused by a variety of factors, ranging from fuel system issues to electrical and hydraulic problems. By identifying the root cause of the cycling and performing regular maintenance, operators can prevent this issue from disrupting operations and ensure the telehandler operates efficiently.
Proper attention to the fuel system, sensors, wiring, idle speed adjustment, and air intake can go a long way in maintaining the telehandler’s performance. If troubleshooting these systems does not resolve the issue, it may be necessary to consult a qualified technician for a more in-depth diagnosis. With regular care and maintenance, the Lull 844 can continue to provide reliable service for years to come.