Why Are Diesel Engines Difficult to Start When They Are cold?

Diesel motors are quite a bit harder to start when cold due to multiple different factors:

• Battery Strain
• Battery Output
• Oil Density
• Gas “Gelling”
• Electrical Resistance

An average battery runs optimally at 80 degrees Fahrenheit.  This is the temperature at which the battery holds 100% charge, but when temperatures get colder, the battery begins to slowly lose function.  At 0 Degrees for instance, an average car battery carries approximately 46% available power.

If operating items such as the heater, lights, radio, or other electricity requiring options in your vehicle, you further reduce the batteries available power towards starting your engine.  If you think your battery may be your problem, you can take it in to a local automotive repair shop and have it tested.

Another leading pair of issues to cold-starting difficulty is your gas / oil density.  As the temperature drops, your oil and gas become thicker, and harder for your engine and fuel pump to move around.  This is just more added stress to the starting process, and with the battery in mind, causes your engine to be nearly five times harder to start than it would be at 80 degrees Fahrenheit.

A few simple solutions to these problems include:

• Keeping a Full Fuel Tank
• Use Glow Plugs or Block Heaters
• Store Vehicle in a Warmer Area
• Winter Diesel Fuel Additive

By keeping your fuel tank full, you further prevent the chance of moisture entering the tank, and freezing, which can block your fuel lines and prevent starting.

If you are able, be sure to store your vehicle inside of a warmer area, such as a heated shed, or garage.  This will greatly increase your starting ability.  However, if you are unable, purchase glow plugs, or a block heater and set it on a timer to warm your engine a few hours prior to your expected starting time.

Lastly, use a winter diesel fuel additive to make your gas burn more efficiently, helping to prevent gelling within your engine.  If your engines pistons are already overly-gelled, take your vehicle to a local automotive mechanic, and have them cleaned and/or rebuilt.

For more automotive answers to commonly asked questions, as well as tips from professionals, visit Scottsdale Muffler & Automotive’s Blog.