Guide on Starting A Diesel With Bad Glow Plugs

April 23, 2022

Checking the glow plug condition in the diesel engine after failed to start the engine.

Glow plugs, of course, are components susceptible to wear over time. As such, there will come a time when your glow plugs will go wrong. Hence, you need to check them every 80,000 to 100,000 km. So, if you’ve been driving your car for several years, it will be best to have the glow plugs checked regularly at the recommended intervals to ensure that they are always in top-notch condition.

Imagine you’ve been driving the same diesel car for several years without any issue or problem. Yet, one day, you tried to start your vehicle, you had a hard time starting it. The next day became only a repeat of the previous day, and from then on, every time you started your car, you noticed black smoke coming out of your car’s exhaust pipe. So, you’re asking: Are these telltale signs that your engine’s glow plugs had gone bad? 

How to Start Your Diesel Engine with Bad Glow Plugs

You should not have any problem starting your engine if your glow plugs are in excellent condition. But if your glow plugs have gone bad, you only need to crank for five seconds. Then, allow five seconds to elapse. Afterward, you should crank again for five seconds and wait for five seconds. Just go on with these cranking intervals, and you can surely get your engine started after several tries.

The diesel engine, of course, doesn’t come with sparkplugs. Instead, they come with glow plugs, which are unique heating components. Without the heat generated by the glow plugs, the diesel engine will have a hard time starting, especially during cold weather. Nevertheless, a quick start will also depend on other factors like engine size, the efficiency of compression, and how quickly you can crank. 

If the engine is in good condition with excellent compression, it should start even if the glow plugs are bad or if the ambient temperature is moderate. But if the ambient temperature is somewhere below five centigrade, the engine will not start without the help of the glow plugs. 

The diesel engine finds it hard to start during cold weather because the boiling point of diesel is high. Moreover, the cylinder head and block are heat hogs, meaning they absorb much heat, rendering the combustion chamber cold. 

Since the glow plugs get positioned inside the internal combustion chamber, they could provide the needed heat to start the engine. They could generate heat to warm up the cylinder and combust fuel. Without glow plugs, your diesel engine will not start in cold weather.

Moreover, glow plugs enable your vehicle to run smoothly. If the weather is moderate, the defective glow plugs will strive and struggle to produce enough heat to increase the temperature inside the cylinder. But in icy weather, the faulty glow plugs will not function at all.

Besides, you might find it hard to start your diesel engine in average warm weather, and you need to crank more. If that happens, however, you can employ the following tricks to get your diesel engine running:

  • First, you can use a starting fluid (ether) to start the car. Yet, you should know how to use this fluid; otherwise, you might be doing more harm to your engine, or you might get yourself burned or injured. 
  • Second, you can ask your buddies to push your car. If it got a manual transmission, you could ask your friend to get your vehicle towed by his car. Then, jack up the pedal while your car gets pushed or towed. 
  • Lastly, you can heat the diesel engine. Your car might not start if the ambient temperature is below ten centigrade. So, one hack is to use a space heater under your diesel engine. Then, blanket your car with a tarp to jack up the engine’s temperature.

Symptoms of Bad Diesel Glow Plugs

The diesel glow plugs are susceptible to damage and wear. So, there will come a time when they would go bad after prolonged and continuous functioning. Hence, it will be helpful if you know the following symptoms of bad diesel glow plugs, so that when they appear, you will understand that the symptoms originate from defective glow plugs:

Poor Acceleration

Your vehicle will not run well if it has defective glow plugs. One telltale sign that your glow plugs aren’t working well is reduced performance from your engine. If you floor, for example, the accelerator, and the car still doesn’t generate much speed, something is wrong with your glow plugs. 

Nevertheless, it is not only bad glow plugs that cause poor acceleration. But if—aside from poor acceleration—you see other symptoms of bad glow plugs, the culprit is most probably bad glow plugs.

Difficulty in Starting the Engine

Since the glow plugs are there to quicken the starting of the diesel engine, if they are defective, you will surely experience difficulty in starting your car. Of course, the pressure and heat, along with the infused air in the cylinder, ignite the diesel fuel. Yet, the engine will experience more pressure if the glow plugs aren’t working well.

Black Smoke

Another indicator that the glow plugs are faulty is the black smoke that emanates from the exhaust pipe. Several reasons might be behind the emergence of this black smoke. Yet, it might indicate bad glow plugs because they dampen the diesel combustion. 

The combustion process, of course, doesn’t necessarily produce black smoke as a byproduct. So, if there is black smoke, it will indeed indicate that something is wrong with your car or that the glow plugs have gone faulty.

Check Engine Light

If the glow plugs are defective, it will engender the lighting of the check engine light. If you scanned via the OBD2 scanner, you would see that it entails a glow plug error code or related to it. One example of this code is PO380 which indicates the glow plug or heater circuit malfunctioning. Yet, there are many other trouble codes like PO382, PO383, and many more.

Is It Alright Even If The Glow Plugs Are Bad?

Glow plugs are subject to wear over time. If they go bad, they negatively affect the vehicle’s performance. The car might start, and you can drive it eventually. But it will not work like when it is working sound. As the glow plugs become less functional, you will need multiple tries to start it.

But if you want to reach higher speeds, you need to floor the gas pedal. Besides, if you live in a colder place, the engine won’t generate sufficient heat to start combustion when you start the engine. Moreover, making multiple attempts to start your car engine will be pretty irritating. 

Furthermore, bad glow plugs will compromise the fuel efficiency of your vehicle while increasing the pollution your car will belch out. So, it will help if you replace your glow plugs promptly when they have already gone bad.

How Much is the Glow Plug Replacement?

The cost of replacing the diesel glow plug is somewhere between $95 to $210. Each glow plug will cost you somewhere between $15 to $50. The labor will be somewhere between $80 to $160. The cost, of course, will depend on how many cylinders your diesel engine has. 

Since each engine cylinder has a glow plug, you will need four new glow plugs if your engine has four cylinders, even if there’s only one bad glow plug. If you only replace one plug, there is a strong likelihood that the unreplaced glow plugs will also go bad. 

Of course, the total replacement cost will also depend on your car’s model and make. Glow plugs, however, are less expensive than sparkplugs. So, if you know how to do it yourself or if you can find someone who charges less, you can decrease the replacement cost.


Car maintenance is necessary to keep a diesel engine running. The glow plugs, as mentioned above, is subject to wear and tear over time. So, you will need to replace them if they exhibit symptoms of being defective. If you happen to see any of the symptoms delineated above, you don’t need to dilly dally, for the more you delay in replacing the bad glow plugs, the more you are putting your car’s engine at risk of developing more problematic issues. 

Therefore, the best thing to do when you see those symptoms is to have your vehicle checked immediately and do the necessary replacement of defective glow plugs. In this way, you can prevent the onset of other issues concomitant with faulty glow plugs.