Thick White Smoke on Startup in Gehl 6640 Skid Steer: Causes and Solutions

[MikePhua]

The Gehl 6640 skid steer is a versatile and reliable piece of equipment used across various industries, including construction, agriculture, and material handling. Like any piece of heavy machinery, the Gehl 6640 can sometimes develop issues, and one common problem that operators encounter is the appearance of thick white smoke during startup. This issue can cause concern, as smoke emissions from machinery can indicate potential mechanical problems. However, understanding the causes of white smoke and how to address them can help ensure the machine continues to perform at its best.
Overview of the Gehl 6640 Skid Steer
The Gehl 6640 skid steer is part of Gehl's 6000 series, known for its power, maneuverability, and durability. With a 60-horsepower engine, this skid steer is capable of handling various attachments such as buckets, forks, and grapples. It's equipped with an efficient hydraulic system, allowing for quick attachment changes and excellent lifting capacity. Like most Gehl equipment, the 6640 is designed to handle tough conditions while offering operators excellent visibility and comfort.
Key Specifications:

• Operating Weight: Approximately 5,800 lbs (2,630 kg)
  
• Engine Power: 60 horsepower
  
• Hydraulic Flow: 16.9 gpm (63.9 l/min)
  
• Rated Operating Capacity: 1,700 lbs (771 kg)
  
• Max Lift Height: 10.5 feet (3.2 meters)
  

Despite its robust performance, the Gehl 6640 is susceptible to the same kinds of mechanical issues that can affect other machinery. One such issue is the appearance of thick white smoke during startup, which can be alarming to operators.
Understanding White Smoke and Its Causes
White smoke from an engine is generally a sign of incomplete combustion, meaning that something is preventing the fuel from burning properly. In diesel engines like the one in the Gehl 6640, white smoke on startup is typically caused by a few common issues. These problems can range from minor to serious, and identifying the cause is essential to determining the appropriate solution.
Common Causes of White Smoke on Startup

1. Cold Weather and Incomplete Combustion
   One of the most common reasons for white smoke on startup is cold weather. Diesel engines, like the one in the Gehl 6640, rely on high compression to ignite the fuel. When the engine is cold, the combustion process may not be as efficient, causing unburned fuel to exit the exhaust as white smoke. This is especially common in extremely cold temperatures when the engine hasn't reached its optimal operating temperature. Once the engine warms up, the smoke typically disappears.
   Solution:
   If the white smoke disappears once the engine warms up, it’s likely that the issue is simply related to cold weather. Ensuring that the engine pre-heats properly, especially in colder climates, can help reduce this occurrence. Consider using a block heater or starting the machine with some warm-up time if cold weather is a consistent issue.
   
2. Faulty Glow Plugs
   Glow plugs are essential for helping start diesel engines in cold conditions. They provide heat to the combustion chamber to assist in ignition. If one or more glow plugs fail, the engine may not start properly, and you could see white smoke as unburned fuel exits the exhaust system.
   Solution:
   If you suspect that the glow plugs are faulty, you should have them tested and replaced if necessary. It’s important to address this issue as soon as possible, as starting the engine with faulty glow plugs can lead to increased wear and tear on the engine over time.
   
3. Fuel Issues (Water in Fuel or Low-Quality Fuel)
   White smoke can also be caused by problems with the fuel. If water has entered the fuel system, it can cause incomplete combustion, leading to the production of white smoke. This is particularly common if the machine has been sitting unused for some time, allowing water to condense inside the fuel tank. Similarly, low-quality fuel or improperly mixed fuel can result in poor combustion and the emission of white smoke.
   Solution:
   To resolve fuel-related issues, ensure that the fuel is clean and free of contaminants. If you suspect water in the fuel, drain the water separator and replace the fuel filter. Always use clean, high-quality diesel fuel to prevent issues with combustion. Regular fuel system maintenance is crucial to keeping your Gehl 6640 running smoothly.
   
4. Injector Problems
   Diesel injectors play a critical role in the combustion process by spraying a fine mist of fuel into the combustion chamber. If the injectors are malfunctioning, they may not deliver fuel in the correct manner, leading to incomplete combustion and the production of white smoke. This can happen if the injectors are clogged, damaged, or worn out.
   Solution:
   Inspecting the injectors for wear or damage is essential if the smoke persists after the engine warms up. Cleaning or replacing the injectors can resolve this issue and restore proper fuel atomization, ensuring that the engine burns fuel efficiently.
   
5. Head Gasket or Cylinder Head Issues
   A more serious cause of white smoke is a blown head gasket or a cracked cylinder head. This can cause coolant to enter the combustion chamber, resulting in thick white smoke. This issue is often accompanied by other symptoms such as engine overheating, loss of coolant, or a noticeable decrease in engine power.
   Solution:
   If you suspect a head gasket or cylinder head problem, it's important to have the engine inspected by a professional mechanic. This is a more costly and complex repair, but it’s necessary to prevent further damage to the engine. Promptly addressing any issues with the cylinder head or gasket can help prevent catastrophic engine failure.
   
6. Turbocharger Issues
   Some diesel engines, including the Gehl 6640, may have a turbocharger that boosts engine performance. If the turbocharger is malfunctioning, it can cause white smoke to appear, especially on startup. This could be the result of oil leakage into the exhaust system or problems with the turbo seals.
   Solution:
   A turbocharger issue requires professional attention. Regularly inspect the turbocharger for signs of oil leakage and ensure it’s functioning correctly. If the turbocharger is damaged, it may need to be rebuilt or replaced.
   

Steps to Take If Your Gehl 6640 is Emitting White Smoke
If your Gehl 6640 is producing thick white smoke on startup, here are some recommended steps to address the issue:

1. Check the Weather Conditions
   If the smoke disappears once the engine warms up, it may simply be a cold-start issue. In that case, ensure that the engine is properly pre-heated in cold weather or consider adding a block heater for easier starting.
   
2. Test and Replace Glow Plugs
   Faulty glow plugs can cause hard starting and white smoke. Have the glow plugs tested and replaced if necessary.
   
3. Inspect the Fuel System
   Check for water in the fuel tank or poor-quality fuel. Drain the water separator and replace the fuel filter to ensure the fuel system is clean.
   
4. Check the Injectors
   Inspect the injectors for wear or clogs. Cleaning or replacing the injectors can restore proper combustion and eliminate white smoke.
   
5. Look for Coolant Leaks
   If the white smoke persists and is accompanied by engine overheating or a loss of coolant, you may have a blown head gasket or cracked cylinder head. Have the engine inspected and repaired as soon as possible to prevent further damage.
   
6. Inspect the Turbocharger
   If your skid steer is turbocharged, check the turbocharger for signs of oil leakage. Repair or replace the turbocharger if necessary.
   

Conclusion
White smoke on startup in a Gehl 6640 skid steer is typically a sign of incomplete combustion, which can stem from a variety of causes. Cold weather, faulty glow plugs, fuel issues, injector problems, or more serious mechanical issues such as a blown head gasket can all contribute to this problem. By systematically diagnosing and addressing the root cause, you can ensure that your Gehl 6640 continues to run smoothly and efficiently. Regular maintenance and prompt repairs will keep your equipment in top shape, reducing downtime and enhancing productivity.