How to Replace GDI Fuel Injectors

Since Gasoline Direct Injection (GDI) is the preferred fuel delivery technology used on most recent vehicles, makes sense learning how to replace these new type of fuel injectors.

The goal of this article is offering you a step-by-step procedure to assist you during this important maintenance regardless of the level of experience you have with GDI injectors.

These instructions are a general outline of what needs to be done to replace GDI injectors. As you can see this is not for the faint of heart. Proper tools are critical, which most hobbyists will not have. This article will at minimum give you an idea of “can I do this myself”.

What tools do You need?

Depending on your application, you may need the following items at hand:

  • An appropriate scan tool compatible with your car make and model
  • Compressed air gun
  • A suitable GDI puller compatible with your high-pressure fuel injectors design
  • Bore cleaning brushes
  • A slide hammer puller is also advisable. Seal sizer kit, consisting in seal expander (cone) and sizer tool
  • Slotted and Phillips screwdrivers
  • Ratchet and socket set ranging from 8mm to 24mm.
  • A set of metric combination wrenches (6mm to 19mm)
  • Assorted pliers of different sizes
  • Screw trays
  • Lint-free towels
  • LED flashlight
  • Safety goggles and appropriate gloves.
  • Fire extinguisher

GDI Tools

In addition to the aforementioned tools, you may also need:

  • Replacement DI fuel injectors
  • Fuel injectors o-ring seals kit
  • Intake manifold gasket and/or seals

Safety always comes first

Gasoline direct injection systems work with pressures in excess of 4,500 psi. That’s why complying with safety protocols it’s so crucial. Aside from the suggestions of the Occupational Safety and Health (OSH) guidelines, keep in mind the following recommendations:

  • Disconnect the negative terminal of the battery to prevent the fuel pump from pressurizing the system.
  • Use the manufacturer procedure to relieve fuel pressure from the system
  • With the help of the scan tool, double-check that fuel pressure was properly released before continuing

Step-by-step procedure for replacing GDI injectors

GDI Fuel Injector

These instructions should be taken as a reference, whenever possible follow the original manufacturer procedure to replace fuel injectors.

CAUTION: it’s extremely important to relieve fuel pressure as indicated in the previous section BEFORE continuing.

1. Let the engine cool down

Most direct injection vehicles have aluminum cylinder heads and aluminum/composite plastic intake manifold. These materials are extremely sensitive to temperature thus we strongly suggest letting the engine to completely cool down before starting.

2. Disconnect vehicle battery

Disconnect the negative terminal of the battery using the appropriate open-ended wrench. Modern vehicles can turn on the electric fuel pump automatically so it’s important to don’t skip this step.

3. Double-check that you have everything at hand

Unlike conventional Multiport Fuel Injection systems, direct injection often requires special tools during the disassembling process. In that regard, obtaining an OEM repair manual for your specific vehicle is a good idea. Check the recommended tools and be sure to have everything at hand before starting.

PRO TIP: don’t skip this step. Some applications force you to buy OEM tools to remove fuel injectors. Save yourself of unnecessary hassle, you may lose gaskets, seals, and even injectors if you ignore this warning.

4. Take pictures before starting

It’s always good to have pictures of electrical connectors, vacuum hoses, and accessories location and orientation. This step may save you a lot of time even if you are a seasoned mechanic. It might be helpful to take pictures at each step. This will give you something to refer to later.

5. Depressurize fuel system (IMPORTANT)

Vehicles fitted with GDI systems require special attention during this step since they work with high pressures. Never underestimate the risk of a pressurized GDI system. Follow the manufacturer's procedure to release the fuel pressure to the letter. Always wear safety goggles and never forget to double-check with the help of a scan tool that fuel pressure was successfully released.

PRO TIP: don’t skip this step. You may get injured in case you forget to fully depressurize GDI system pipes.

6. Remove any necessary component to access injectors

  • Use adequate hand tools to disconnect accessories, sensors, plates, vacuum lines, electrical harnesses, and connectors. Refer to your vehicle repair manual for detailed instructions
  • Carefully remove the intake manifold
  • Remove the intake manifold gasket

PRO TIP: It’s a good practice to cover the intake manifold inlets with a lint-free cloth or rag to prevent any tool/bit/dirt from accidentally falling inside the engine

7. Carefully remove the high-pressure fuel rail and fuel pipe

  • Use adequate pliers to disconnect fuel injectors electrical plugs
  • Carefully remove the fuel pipe.
  • Use the appropriate tool to loosen the fuel injector rail
  • Carefully remove the fuel rail, take special care with fuel injector’s connectors

PRO TIP: depending on your application you may require one or more special tools to remove the fuel rail. Do not attempt to force out the fuel rail since you could damage it.

8. Remove old fuel injectors using the proper extractor

This is the step that definitely separates GDI systems from familiar fuel injection systems. It’s extremely important to proceed with maximum care during injectors removal and use manufacturer recommended tools for this purpose.

*Using compressed air get rid of debris, dirt, and any other material surrounding fuel injectors. Remember, unlike conventional injectors, DI injectors deliver fuel directly to the combustion chamber. You must ensure that no dirt enters the engine. In fact, if you want big trouble let a screw fall into the hole.

Using an adequate fuel injector removal tool carefully loosen each injector.

  • Gently pull injectors taking special care to not forcing them on their way out.

PRO TIP: depending on your application you may need a slide hammer tool to remove injectors. Only use such a tool as a last resource in case injectors are too tightened. Be aware that knocking DI injectors with a slide hammer will probably damage them thus you won’t be able to reuse those injectors.

9. Recondition old injectors (OPTIONAL)

Using appropriate extraction tools ensures that you can remove GDI injectors without damage allowing you to reuse them. If that’s the case, you will need to recondition injectors by replacing the necessary seals.

  • Cut off the Teflon seal at the tip of the injector
  • Remove the upper o-ring and separator
  • Replace fuel injector’s internal filter (if any)
  • Now, using the special cone part of the seal sizer kit, expand the new Teflon seal. Do not lubricate the seal with oil or grease
  • Place the cone on the injector tip and carefully push the Teflon o-ring into the injector’s groove
  • Next, use the sizer sleeve to press the dry Teflon seal into the groove. This is the most important step, take your time to avoid damaging the seal
  • Replace the upper seal and separator
  • Repeat the procedure for each injector. Double-check all seals, especially Teflon seals

Keep in mind that this type of injector is installed directly in the cylinder head. Any mistake during lower seal installation may lead to compression and fuel leaks.

GDI Injector

10. Reinstall injectors in the cylinder head

Regardless of whether you have chosen to reuse old injectors or if you have decided to order a new set at Mike's Carburetor Parts, you must reinstall them making sure no dirt gets into the engine. In that regard is strongly suggested to:

  • Perform a thoughtful cleaning of injectors’ seats using bore cleaning brushes
  • Spray an appropriate GDI cleaner with no lubrication agents
  • Dry the injectors’ bores with clean, oil-free, compressed air
  • Gently reinstall each injector. It’s important to avoid damage to the Teflon seal during this step. Compress again the seal with the sizer tool if necessary
  • Once you reinstalled all injectors you can use a small amount of engine oil to lubricate the upper seals. Avoid oil to reach the cylinder head or the lower Teflon seal
  • Reconnect each injector electrical plug

11. Reinstall high-pressure fuel rail

  • Line up injectors with their respective holes in the fuel rail and then firmly press down until the o-rings are fully seated.
  • Tighten injector rail bolts, it’s advisable to use a torque wrench to ensure proper tightening according to OEM specifications.
  • Reconnect fuel pipe.

PRO TIP: some car makers recommend replacing the fuel pipe during this step. Refer to your vehicle’s repair manual for further information.

12. Reinstall intake manifold and other components

  • Replace intake manifold gasket.
  • Using the appropriate tools reinstall the intake manifold. Tighten it evenly to avoid vacuum leaks.
  • Reinstall all accessories, brackets, plates, vacuum lines, wiring harnesses, and components.
  • Reconnect the negative battery cable

13. Verify that no fuel or vacuum leaks are present

  • Pressurize the fuel system by turning the ignition switch to ON position and/or using the scan tool.
  • Perform an initial fuel leak test.
  • If everything goes as expected, then start the engine.
  • Wait until the idle stabilizes and then use the flashlight to perform a second inspection for fuel leaks.
  • If the idle doesn’t stabilize it could be an indication of vacuum leaks. Double-check that you didn’t miss to reconnect MAF or MAP sensor before removing the intake manifold.

14. Check DTCs and perform a test drive

  • Clean any data trouble code present in memory
  • Perform a complete test drive to allow the fuel system to fully pressurize to its normal value
  • Check again DTCs as well as fuel leaks

These instructions are a general outline of what needs to be done to replace GDI injectors. As you can see this is not for the faint of heart. Proper tools are critical, which most hobbyists will not have. This article will at minimum give you an idea of “can I do this myself?”.

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