5.9 Cummins Excessive White Smoke

To fix white smoke from your Cummins 5.9L engine, you must first diagnose the underlying issue. Each root cause has unique warning signs you can look out for.  

Faulty or Leaking Injectors 

Injector-related problems that can cause excessive white smoke include: 

• Clogged injectors: Clogged or dirty injectors disrupt fuel atomization and cause excess fuel to burn incompletely. Cleaning the injectors will restore them to proper function.
• Leaking injectors: Leaking injectors allow fuel to enter the combustion chamber, leading to incomplete combustion and white smoke. Replacing severely damaged injectors should fix the problem.   

Coolant Leak into the Combustion Chamber

In addition to white smoke, you might also notice a sweet smell from the exhaust, a clear sign of burning coolant in your 5.9L Cummins. Common causes include:

• Blown head gasket: A damaged gasket allows coolant to seep into the combustion chamber, where it burns along with the fuel and produces white smoke. To diagnose the problem, check for coolant contamination in your engine oil. If coolant is present, the oil will appear milky or frothy. 
• Cracked cylinder head or engine block: Cracks in these components allow coolant to enter the combustion chamber directly, resulting in the same symptoms. Check the head gasket for signs of damage or leaks and do a compression test to check for pressure loss in the cylinders. 

If white smoke is caused by a blown head gasket, cracked cylinder head or engine block, repair or replace the damaged components to resolve the issue. 

High Fuel Pressure or Over-Fueling

High fuel pressure or over-fueling can cause white smoke, particularly during acceleration or when the engine is under load. Here are a few reasons these issues may occur:

• Faulty fuel pressure regulator: A malfunctioning regulator allows too much fuel to flow into the combustion chamber, disrupting the air-to-fuel ratio and causing incomplete combustion. To fix this issue, check the fuel pressure using a diagnostic tool and adjust or replace the fuel pressure regulator if necessary. 
• Clogged fuel return lines: Blocked fuel return lines prevent excess fuel from flowing back to the tank, which results in over-fueling and inefficient combustion. This issue causes persistent white smoke and higher fuel consumption. Inspect the fuel return lines and clean or replace them to ensure proper fuel flow. 

Overly Rich Fuel Mixture

An overly rich fuel mixture can cause white smoke, loss of power, and engine stalling in a Cummins 5.9L. Possible causes of these issues include:

• Dirty air filters: Dirty filters restrict airflow into the engine, resulting in an overly rich fuel mixture. It’s best to clean or replace the air filter to restore airflow and balance the air-to-fuel ratio.
• Faulty mass airflow (MAF) sensor: Faulty MAF sensors can incorrectly measure the amount of air entering the engine, leading to an improper air-to-fuel ratio and an overly rich mixture. You might notice white smoke, hesitation during acceleration and poor fuel efficiency until you clean or replace the sensor. 

Cold Weather or Short Trips

If you notice white smoke during cold starts or short trips, it should clear up as the engine warms. Here are the potential causes:  

• Condensation in the exhaust system: In cold weather, condensation forms inside the exhaust system. When the engine starts, this moisture converts into steam and appears as white smoke. Once the engine reaches its operating temperature, the issue should resolve itself. 
• Cold diesel: At low temperatures, diesel fuel can thicken, making it hard for the engine to atomize correctly. This consistency leads to incomplete combustion and white smoke. As the engine warms, the fuel should atomize more effectively, and the smoke should disappear. 

There are a few ways to diagnose Cummins 5.9L white smoke, including:

• Visual inspection: Observe the white smoke as the engine warms up. If the smoke dissipates, it may be due to condensation from cold weather. If a sweet smell comes from the exhaust or the coolant level is low, it may indicate a blown head gasket or cracked cylinder head.
• Compression test: Perform a compression test to identify low compression in the cylinders. Low compression could indicate a blown head gasket or other internal engine damage, allowing coolant to enter the combustion chamber. 
• Fuel system inspection: Check the fuel pressure with a gauge and inspect the fuel injectors for leaks or signs of excess fuel, which could cause an overly rich fuel mixture and white smoke.
• Diagnostic tools: Use an OBD-II scanner — an electronic device that plugs into your vehicle — to check for error codes related to key components, such as a faulty fuel pressure regulator or malfunctioning MAF sensor.

Prevent white smoke and boost your 5.9L Cummins engine’s performance with our third-party tested additives. 

Hot Shot’s Secret Diesel Extreme

Add Hot Shot’s Secret Diesel Extreme to your fuel tank to clean injectors, optimize combustion, and effectively reduce emissions.

Hot Shot’s Secret Diesel Extreme is a powerful fuel system additive that restores efficiency and tackles stubborn buildup in your engine. It thoroughly cleans injectors, reducing carbon deposits and fuel residue in the combustion chamber and resolving issues that cause white smoke, like poor fuel atomization.

Hot Shot’s Secret Everyday Diesel Treatment (EDT)

Add Hot Shot’s Secret Everyday Diesel Treatment to your fuel tank during regular fill-ups to maintain injector health, optimize performance and improve fuel economy.

This concentrated six-in-one additive enhances and protects modern diesel fuel systems by providing fuel system cleaning, injector lubrication and water removal, which reduce the risk of injector clogging and improper fuel atomization causing white smoke. It boosts cetane by up to 7 points and improves fuel mileage by up to 7.3%.