How To Test 7.3 Powerstroke Glow Plugs? (Step By Step)

Having engine issues such as – taking a long time to start, engine misfiring & getting smoke from the exhaust are great indicators of faulty glow plugs. 

If you’re wondering how to test 7.3 Powerstroke glow plugs, this article is for you. In this article, I’ll be guiding you on how to test them with & without removing them at all. 

Glow Plug: What is It & What Does It Do?

Diesel engines require a high temperature to ignite properly. Though the engine can produce enough heat in the summer, it fails terribly in the cold weather. 

In cold weather, the diesel engine can’t produce enough heat & takes help from the glow plugs. Glow plugs generate massive amounts of heat for a few seconds & help the engine to ignite. 

Whether you have a 4, 6, or 8 cylinder engine, each engine cylinder has a glow plug on top of them. If any of the glow plugs become faulty, the whole engine system malfunctions. 

Note: Glow plugs and spark plugs aren’t the same. Spark plugs continuously produce heat while the engine is running & the glow plugs produce heat once in a while for the engine to get started. 

Testing 7.3 Powerstroke Glow Plugs:

You can test your 7.3 Powerstroke glow plugs in two ways – removing them from the cylinder & without removing them. Stay tuned as I’ll be explaining both of the procedures steps by step. 

How To Test Glow Plugs Without Removing Them

You can easily test your glow plugs without removing them from the engine. According to your truck model, all you’ll need is a car LED bulb & a basic screwdriver kit. 

Firstly, attach two wires to the LED bulb as you’ll be connecting them to the battery & glow plugs (one by one). Now follow the steps mentioned below to check your glow plugs:  

  • Step 1: Connect one bulb wire to the positive part of the battery & keep the remaining wire in your hand. 
  • Step 2: Check whether the bulb is working via touching the ground with the second wire; it’s good if the bulb lights up. 
  • Step 3: Touch all the glow plugs with the second wire one by one & inspect the brightness of your bulb. 

Result Part: 

  • The glow plugs causing full brightness of the bulb are good
  • The glow plugs causing dim brightness of the bulb are weak.
  • The glow plugs causing zero brightness of the bulb are bad

You should always replace the weak & bad glow plugs for optimum engine performance. 

How To Test Glow Plugs By Removing Them 

This segment is for you if you want to check the glow plugs by detaching them from the engine. It’s relatively harder than checking glow plugs kept in the cylinder. 

I hope you know well how to detach the glow plugs first. If so, let’s get started with the basic instructions of detaching glow plugs along with how to test them: 

  • Step 1: Remove the air filter 
  • Step 2: Remove the main connector from the engine harness
  • Step 3: Remove the bracket mounting towards the valve cover
  • Step 4: Remove the valve cover & valve cover gasket 
  • Step 5: Unclip the clippers of glow plugs
  • Step 6: Carefully remove them. You can use a plastic suction tube to aid this process. 
  • Step 7: Take your multimeter & set the resistance at 200ohm
  • Step 8: Test each of the glow plugs. If you find any readings other than 0.5 to 2.0, your glow plug is faulty. 

Make sure to set the multimeter correctly, or else you’ll get wrong readings while testing your glow plugs. 

How Often Should You Test Your Glow Plugs?

Most glow plug’s lifespan is around 100,000 miles. That being said, you should test & replace your glow plugs after every 100,000 miles of driving. 

Cost Of Replacing Glow Plugs in 7.3

Each glow plug costs around $10 & a full set of eight glow plugs costs $70 to $80. That’s it; now add an extra $75 to $150 per hour of labor cost if you’re getting the replacement done from an auto shop. 

Frequently Asked Questions – FAQ 

Do I Need Glow Plugs To Start My Engine?

You do need glow plugs to start your engine – but not always. Glow plugs are a must for your engine in the cold weather when the engine itself can’t produce enough heat at the start. 

Should I Replace One Defective Glow Plug or The Entire Set?

Glow plugs are very cheap. If you find one of the glow plugs being faulty, chances are – others are on the way to death as well. That’s why it’s better to replace the entire set of glow plugs instead of just the faulty one. 

How Do I Know If My Glow Plugs Are Bad? 

Your engine will take more time than usual to start & you’ll hear weird noises from the engine. Besides, white smoke (white & black) from the exhaust & engine misfiring are also symptoms of bad glow plugs. 


You can test your glow plugs with/without detaching them from the engine. Still, I wouldn’t recommend newbie or not-so-knowledgeable users to detach their glow plugs to test them. 

I hope this article served enough value knowing how to test 7.3 Powerstroke glow plugs. Now you can test them on your own without rushing to your nearby auto shop.

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