Signs of Failing Diesel Glow Plugs
Diesel engines operate at high temperatures, and glow plugs keep your diesel engine’s operating temperature sufficiently high. Should diesel glow plugs begin to fail, the engine won’t run as efficiently and may not even start in current conditions.
What Are Diesel Glow Plugs?
Diesel glow plugs are a heat-generating element found in diesel engines. Your diesel vehicle’s engine has a glow plug for each cylinder in the engine. The plug may be in the pre-chamber (for pre-chambered diesel engines) or in the actual combustion chamber (for direct-injection engines).
What Do Diesel Glow Plugs Do?
A diesel glow plug might be thought of as a spark plug on steroids. The two are different components and can’t be substituted for each other, but they perform a similar function. Diesel glow plugs just do it to a much higher degree (pun intended).
The function of a spark plug is to create a spark and heat that will cause ignition within an engine’s combustion chamber. These plugs work well in gasoline engines, but they don’t create enough heat for diesel engines.
Diesel glow plugs likewise create heat, but they generate much more than a spark plug does. This extra heat is necessary because diesel engines operate at much higher pressures than gasoline ones do.
Diesel glow plugs are absolutely necessary when starting a diesel engine in cold weather. If you’re driving through the Rockies during winter, for example, a diesel vehicle likely won’t start if glow plugs aren’t working.
These plugs aren’t just for cold-weather driving, though. Even when driving in Nevada during summer, the cylinder block and cylinder head draw a significant amount of heat away from the combustion chamber because they’re metal. Diesel glow plugs replenish the heat that is lost through conduction.
What Are Signs of Failing Diesel Glow Plugs?
Should one or more of your vehicle’s diesel glow plugs begin to fail, there are four main signs that you may notice.
Engine misfires are often the most common sign that a glow plug has failed, but a failed glow plug isn’t the only potential cause of a failed glow plug. When a glow plug doesn’t produce sufficient heat, misfires can occur within engine chambers.
Any engine misfire will result in a loss of power because at least one cylinder doesn’t combust properly. Loss of power is most likely to be noticed during acceleration, and you might also see a drop in fuel efficiency.
Hard starts can also develop if a glow plug isn’t functioning properly, for the glow plug is instrumental in heating up the cold engine. You’re most likely to notice this during cold temperatures and when your vehicle has sat unused for some time.
Black exhaust smoke can also emit from your exhaust when a glow plug fails. This is a sign of a problem within the combustion chamber.