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How to Know if Your Glow Plugs Are Bad

October 23, 2014
By Jeffery White

With winter just around the corner here in Calgary, it’s going to be more important than ever that your diesel engine has glow plugs supporting it. Though diesels have many advantages over gasoline engines, their lack of spark plugs means they often need glow plugs in order to start. When winter comes, diesel can congeal if temperatures get below about 4.5°C. At that point, glow plugs are used to heat the engine so you don’t experience any issues.

One of the first ways you’ll notice, then, that your glow plugs are bad is if your diesel engine doesn’t start promptly in cold weather or if it takes you several tries before it does. Odd sounds you wouldn’t normally hear when you turn the key may also mean an issue exists with your glow plugs. Even if the normal sounds you hear are just louder or more pronounced, faulty glow plugs may be at the root of it.

If you get it up and running, pay attention to how it drives. If the engine sputters, jerks, or it makes louder sounds than you’re accustomed to, your glow plugs are probably on their last legs. Sometimes the engine will start just fine, but you’ll experience these issues when you start actually driving the vehicle, which is why it’s so important to keep a weathered ear at all times.

Sometimes these issues may be similar to what would occur if you were low on diesel. Other times, the earliest warning signs are extremely subtle, like if your vehicle seems to skip every few minutes.

Of course, the dashboard of your diesel should also feature a notification that your glow plugs are struggling (it usually appears as squiggly lines). Obviously, when this light goes on, your plugs are in trouble. However, sometimes, the light will come on intermittently. You could even miss it if you weren’t paying attention. In the winter, then, make sure you’re constantly checking in on this light (while driving safely). If you catch glow plugs before they absolutely need to be replaced, you can avoid a number of problems, like being stranded in a Calgary winter without an engine that functions properly.

Fortunately, glow plugs are very affordable and the labor involved in replacing them is not costly. The important thing is understanding the above warning signs and knowing when it’s time to get your diesel engine in front of a professional. While winter is generally when problems occur, it’s just as important to be vigilant in warmer weather too.

The information on this page may have changed since we first published it and is for informational use only and is no substitute for actual professional advice. If you’d like to establish a relationship, reach out to us and we’ll tell you how we can make it official.