6.6 Duramax Difficult Cold Start

Formulating high-quality additives that address and prevent Duramax cold start issues is one of the areas in which we excel at Hot Shot’s Secret. Some causes of difficult cold starts include poor fuel quality and glow plug malfunctions. In freezing conditions, diesel is harder to ignite in the engine additionally fuel gelling and icing create greater challenges. Keep your ride fully winterized and starting reliably by diagnosing the cause and taking effective preventive measures.

Common Causes of a Difficult Cold Start in a 6.6L Duramax

Several things could be causing difficult cold starts for your 6.6L Duramax.

Poor Fuel Quality

Poor or contaminated fuel can prevent proper engine combustion, especially in colder weather when fuel can gel or lose its efficiency. Since a diesel engine has no spark plugs, the cetane level is important for aiding the starting process in cold weather. Substandard fuel may also result in deposits that hinder engine performance, especially in lower temperatures.

Difficulty starting is the main characteristic of poor fuel quality, as diesel fuel can thicken and gel in low temperatures. Other symptoms include increased exhaust smoke during startup and rough idling.

Glow Plug Issues

Glow plugs are essential for preheating the air/fuel mixture in the combustion chamber, which makes starting easier in cold weather. Diesel engines rely on compression to ignite fuel, and the heat emitted by glow plugs makes this process smoother.

Symptoms of faulty or ineffective glow plugs include hard starting, rough idling and excessive smoke during startup. These issues may be particularly evident during cold weather when heating is crucial for starting the engine.

The first thing to do when tackling cold start issues in a Duramax engine is to perform a thorough visual inspection of all components. Look out for:

• Visible damage to glow plugs or fuel lines
• Signs of water contamination in the fuel

If you notice any irregularities or damage, replace faulty glow plugs and treat the fuel system with Diesel Extreme. Next, check the fuel system and test the new glow plugs.

Test the Glow Plugs

Use the following two steps to check the glow plugs:

1. Evaluate all glow plug wiring for breaks or cracks in the insulation. Each glow plug should have 4.7 V going to it during the glow-plug cycle.
2. If the wiring and voltage are in good condition, measure the resistance across the glow plug to see if it is within specification. Anything over 1 ohm is too much resistance.

An “OL” reading on your DMM means there is no continuity in the circuit, and the glow plug is bad.

An individual glow plug problem will be associated with a DTC ranging from P0671-P0678.

Occasionally, the glow plug controller module itself can be defective and needs to be replaced.

Replace any glow plugs that do not pass the test and retest to ensure proper cold start performance.

Check the Fuel System

Low temperatures can cause the fuel in the tank and fuel filter to gel and exacerbate the occurrence of clogs due to wax in diesel solidifying. Check for blockages in the fuel filters and treat with Diesel Winter Rescue to liquify the fuel, remove water and improve fuel lubricity.

Prevent fuel starvation due to icy temperatures, add EDT+ Winter Defense, which prevents gelling and enhances engine performance.

Improve your starting performance with scientifically tested fuel additives that give your engine the boost it needs to cope in cold conditions.

For cold start issues in your Duramax, we recommend the following products:

• Diesel Extreme: Improve fuel quality, clean injectors, and help restore engine performance.
• Everyday Diesel Treatment (EDT): Enhance fuel lubricity and cetane to enhance engine performance. 
• EDT+ Winter Defense: Prevent fuel from gelling with an excellent preventive measure for cold start problems.

Contact one of our experts for more information, or purchase our fuel additives online today!