top of page

How to Replace GDI Injector Combustion Seals

Anytime a gasoline direct injector (GDI) is removed from the engine, its combustion seals must be replaced. Here's why, and how, it's done.

Why GDI Combustion Seal Replacement is Critical

A commonly overlooked step of GDI injector replacements is that even when only one injector is serviced or installed, all of the injectors on that fuel rail must have their combustion seals replaced.

GDI injectors operate directly within the combustion chamber, where pressures often exceed 1,200 PSI and temperatures range from 1,000-2,800-degrees Fahrenheit. Reused or failed seals will result in combustion gas leakage and will erode the injector bore causing permanent and costly damage to the cylinder head and fuel injector.

In addition to the cooling system of the engine, GDI seals function as an added layer of protection against systemic heating of the engine components by preventing hot combustion gases from escaping the combustion chamber past the injector.

GDI combustion seal material is critical. Early model GDI systems used combustion seals made of 100% Teflon and were typically white in color. As GDI systems evolved, other materials were added to the Teflon to enhance longevity and sealing performance. Current model GDI combustion seals are typically black in color and are made of a combination of Teflon-base material with added carbon to improve heat resistance.

Replacement Tips, Procedure & Warnings

While replacing GDI combustion seals is not technically challenging, proper tools and procedures are necessary to ensure that the seals function properly.

To install the new seal, it is critical that the manufacturer-recommended GDI combustion seal replacement tool kit is used. An example of the tool kit is shown throughout the installation procedure section of this article.


1. Remove the old combustion seal using a single-edged razor blade. Using the blade, make a diagonal cut across the seal and pull the seal off the injector.

2. Inspect the groove carefully to ensure there is no dirt or carbon deposits on the sealing surface. Clean as necessary.


Warning. Do not use any lubricants or oils during this procedure. Lubricants and oils on the new seal can ruin its sealing capability and cause a leakage.

1. To install the new combustion seal, use the specific manufacturer-recommended GDI combustion seal replacement tool kit that includes an expansion cone, installation tool, and a compression cylinder. Sometimes, there may be more than one compression cylinder.

2. The new combustion seal will not fit over the injector unless it is expanded. To expand the seal, first place the expansion cone on the end of the injector so that the two are aligned. Next, place the combustion seal on the expansion cone.

3. Place the installation tool over the expansion cone.

4. Using the installation tool, push the combustion seal toward the injector as much as possible. In some cases the install tool can have two internal sizes and will need to be flipped to install the seal on the injector. Use the installation tool to push the seal over the tip of the injector so that it sits on the sealing groove of the injector. Remove the expansion cone.

5. After completing the previous step, the combustion seal will be extremely loose-fitting on the injector from being expanded during the previous step, as shown below. This is normal - but the seal must be resized back to its sealing dimensions using the compression cylinders. These compression cylinders have a progressive taper in them, allowing the seal to properly resize around the injector.

6. To begin resizing the combustion seal, use the larger compression cylinder. Push the compression cylinder over the seal fully, until it slides over the seal or bottoms on the injector. Remove this compression cylinder.

7. After completing the previous step, the combustion seal is closer to its original sealing dimensions, but still fits loosely, as shown below.

8. To finish resizing the combustion seal, use the smaller compression cylinder. Push the compression cylinder over the seal fully, until it slides over the seal or bottoms on the injector.

9. After completing the previous step, the combustion seal should be properly resized and installed in the injector's sealing groove, as shown below. The GDI combustion seal replacement procedure is complete.

Additional Information

Remember to Replace O-rings, Insulator Seals & Retainer Clips!

In addition to its combustion seals, three other components must be replaced when servicing a GDI injector. The below graphic outlines these additional components.

Do not overlook the replacement of the fuel inlet tube o-rings at the top of the injector, which seals the injector on the fuel rail. These o-rings require replacement any time the injector is serviced.

Some injectors also have special insulators and clips. Insulators reduce noise that the injector transmits into the passenger compartment as well as prevent water intrusion into the injector bore, which is exposed to under hood elements. Defective or compromised insulator seals can result in water intrusion and severe injector bore corrosion.

Some manufacturers also require replacement of the retainer clips that hold the GDI injector on the fuel rail any time the injector is replaced. Consult the vehicle-specific service manual to see if this is a requirement for your vehicle.

Hard to Find or Previously Dealer-Only Seal Kits

GB Remanufacturing offers a complete line of injector seal kits. Each seal kit includes the necessary o-rings and seals to properly reseal the injector, which is a recommended practice any time the injector is removed. Each kit services one injector and includes hard to find or previously dealer-only components. To learn more, contact the GB Reman sales team.


Curious to learn more? Visit our Knowledge Center, packed with fuel injection-related articles and topics to encourage a better understanding fuel injection systems and technologies.

bottom of page