Replacing Fuel Injectors In G20: Step-By-Step Guide

The Infiniti G20 fuel injector is a fuel metering device that sprays atomized droplets of fuel into the engine's intake manifold or directly into the combustion chamber. When the fuel injection system, including the fuel injectors, malfunctions, it can cause a rough idle, loss of power, or misfiring. A faulty solenoid may also cause a trouble code to be set in the PCM, resulting in the check engine light illuminating. Replacing a fuel injector involves relieving the pressure in the fuel rail, removing the injector, and installing a new one. The process requires specialised tools and knowledge of the engine and fuel system. The cost of replacing a fuel injector varies depending on the vehicle's location and the number of injectors being replaced.

When to replace the fuel injector

Fuel injectors are electronically-controlled valves that supply pressurised fuel to your engine. They are essential to maintaining peak performance in all driving conditions.

When to Replace Fuel Injectors

Rough idle, loss of power, or misfiring

Poor engine operation has many causes, but faults in the fuel injection system, including the fuel injectors, are high on the list of possibilities.

Odor of raw gas or visible leaks

If you notice any fuel odour around your car, the possibility of a leaking fuel injector should be considered. There should be no external leak from a fuel injector. If an externally-leaking injector is suspected, do not start your car due to the fire hazard.

Check engine light

Some fuel injection failures, for example, a faulty solenoid, may cause a trouble code to be set in the PCM and that will cause the check engine light to illuminate. The codes are read and the fuel injector is tested directly, as needed.

Major engine repairs, engine replacement, or lengthy storage

All fuel injectors will have deposits given enough mileage. These deposits can cause an imbalance in the performance of the injectors from cylinder to cylinder. When an engine is already disassembled, or if you are installing a new engine, that is a perfect time to service the injectors as a set. All injectors have tiny internal filter baskets. A professional injector service facility will clean each injector ultrasonically and replace these filters for a relatively low cost.

Preventative maintenance

You can also take preventative measures to prolong the life of your fuel injectors. Using high-quality (Tier One) gasoline may reduce deposits on fuel injectors.

How to remove the fuel injector

Firstly, ensure the engine is cold. Then, relieve the pressure within the fuel rail by briefly running the engine with the fuel pump fuse removed.

Next, remove the upper plenum on the intake manifold, along with any cables, hoses, or wiring that may restrict access. Detach the supply and return lines from the fuel rail, and then unlock and remove the electrical connectors from each fuel injector. Now, unbolt and remove the fuel rail from the intake manifold.

The injector(s) requiring replacement can now be removed from the fuel rail. Be careful not to let any debris enter the exposed openings. An O-ring seal usually holds the injector very firmly, so you may need to use a screwdriver to remove it.

Once the injector(s) have been removed, the fuel rail should be re-installed, and the supply and return lines re-connected. Finally, the engine can be run and carefully checked for leaks.

If you are removing the fuel injector from a BMW F30, the process is slightly different. First, expose the fuel injectors by removing the engine cover and the foam noise-reduction pad underneath. Then, disconnect the wiring from the cylinder head by lifting the locks on the ignition coils and unplugging the harness from each. Remove the ignition coils by pulling up on them.

Next, disconnect the VANOS plug and the high-pressure fuel pump from the wiring harness. Then, disconnect the fuel injectors by prying back on each injector where the wiring harness plug connects.

Before disconnecting the fuel lines, move a bracket off the back of the valve cover and remove it. Then, disconnect the high-pressure feed line from the pump to the rail, followed by the high-pressure and low-pressure lines from the engine.

Now, remove the fuel rail by loosening the four fasteners that mount it to the valve cover. Finally, remove the injectors using an injector removal tool. Place the tool onto the valve cover in the same orientation as the injector hold-downs, and thread in the brass pieces through the blue girdle, tightening them onto the top of the injectors. Tighten the girdle to the valve cover, and then back out the brass pieces using a pair of adjustable pliers or an adjustable wrench. If successful, the injectors will be pulled out by the brass pieces.

How to install the new fuel injector

Firstly, ensure the engine is cold. Then, release the fuel pressure by turning the car on and removing the 15A fuse that controls the fuel pump from the fuse box under the dash. The car will stall in around 10-15 seconds, at which point you should reinstall the fuse.

Loosen the bolts holding the cables on the accelerator bracket, and then move the cables out of the bracket. Next, remove the three bolts holding the bracket in place. Remove the two bolts on the bracket holding the evap solenoid, and then remove the two rubber hoses connected to it. Undo the plug that connects to the solenoid (it should be blue). Now, remove the bracket and set it aside.

Pull out the fuel pressure regulator vacuum hose from the intake manifold. Now, you should have enough room to remove the plugs from each injector. Once the plugs are off, move the harness out of the way. Pull the PCV out of the valve cover.

Locate the fuel pressure regulator. If possible, remove the hose from the back of the FPR. If not, you will need to unscrew it and pull the FPR out of the fuel rail. You will likely experience some fuel spillage, which is okay.

Now, locate the two fuel lines below the throttle body and remove the hoses. Remember to wear gloves and turn and pull at the same time.

There are two bolts holding down the fuel rail. If you can get a socket on them and loosen them, great; this will save you time. If not, you will need to move the intake manifold back about an inch to allow access. All the bolts are 12mm, and you will need to reach some from the bottom of the car.

Once the bolts are removed, pull the fuel rail out. To remove the injectors from the fuel rail, pull out the aluminum clip holding the injector in, and then remove the injector. Ensure that the O-rings remain on the injector and not in the fuel rail or engine head. Use a screwdriver to remove any O-rings that remain in the fuel rail.

Before installing the new injectors, put a little motor oil on all the rubber O-rings. Don't forget the aluminum clips. Reinstall everything in the reverse order, ensuring that the O-rings are not damaged.

Finally, run the engine and check carefully for leaks, before road-testing the vehicle.

Calibrating the new fuel injector

Release Fuel Pressure:

Before beginning any work on your fuel injectors, it's essential to release the fuel pressure in the system. Turn on your G20, locate the fuse box under the dash, and remove the 15A fuse that controls the fuel pump. The car will stall in about 10-15 seconds. Once stalled, reinstall the fuse.

Disconnect Components:

Loosen the bolts holding the cables on the accelerator bracket and move the cables out of the bracket. Remove the bracket by loosening its bolts and taking out the two bolts holding the evap solenoid. Disconnect the two rubber hoses and the blue plug from the evap solenoid.

Access the Fuel Injectors:

Remove the fuel pressure regulator vacuum hose from the intake manifold. Disconnect the plugs from each injector and carefully move the harness out of the way. Pull out the PCV from the valve cover.

Remove the Fuel Rail:

Locate the fuel pressure regulator and, if possible, remove the hose from the back. If not, carefully unscrew it and pull it out, being prepared for some fuel spillage. Disconnect the two fuel lines below the throttle body. To access the fuel rail, you may need to move the intake manifold slightly. Remove the bolts holding the fuel rail in place and carefully lift it out.

Replace Fuel Injectors:

Remove the old injectors from the fuel rail by pulling out the aluminium clip holding each injector. Ensure that the O-rings remain on the injector and not in the fuel rail or engine head. Install the new injectors by placing a small amount of motor oil on the O-rings and inserting them into the fuel rail. Don't forget to use new injector clips if required.

Calibrating the Fuel Injector:

Connect the fuel injector to the fuel rail, pump, and regulator, replicating the setup in the vehicle. Ensure you're using the correct regulator pressure for your G20. The injector should spray into a collection vessel, either a graduated cylinder or a test tube.

Measuring Injector Opening Time:

The injector opening time is crucial to measure. Actuate the injector several times at a consistent duration, for example, 1.5 milliseconds one thousand times. You can connect it to a controller and "fake" the speed signal to get it to inject. By plotting the amount of fuel delivered against injection duration, you can determine the injector opening time from the graph.

Measuring Open-Injector Fuel Flow Rate:

To measure the fuel flow rate, power up the pump and open the injector for several seconds. Ensure the injector doesn't overheat. Measure the amount of fuel delivered and the time it was held open. Calculate the fuel flow rate by dividing the weight of the fuel by the time. For example, 25 grams of fuel delivered in 10 seconds gives a flow rate of 2.5 grams per second.

Final Steps:

Reinstall the fuel rail and all other components in reverse order. Run the engine, carefully check for leaks, and take your G20 for a road test.

Remember, always exercise caution when working on your vehicle, and if you're unsure about any steps, consult a qualified mechanic.

Safety precautions

Before You Begin

• Ensure you have the right tools, including gloves and safety goggles, to protect your eyes and skin from fuel exposure and accidental injuries.
• Work in a well-ventilated area to avoid inhaling harmful fumes.
• Have a fire extinguisher nearby as a precaution.

Disconnecting the Battery

• Disconnect the battery to prevent electrical short circuits or sparks, which could ignite fuel vapours.
• Loosen the nut on the negative terminal first, identified by a minus sign (-) or black cover. Remove the negative cable and secure it away from the battery.
• Repeat for the positive terminal, marked with a plus sign (+) or red cover.
• Always disconnect the negative terminal first to avoid any electrical arcing.

Relieving Fuel Pressure

• Relieve the fuel system pressure to prevent fuel spray during the replacement process.
• You can do this by pressing a valve on the fuel line or pulling the fuel pump relay and cranking the engine for a few seconds.

Removing the Old Injectors

• Locate the fuel rail, which houses the injectors.
• Detach any electrical connectors from the injectors by pressing the tabs and pulling gently.
• Remove the bolts securing the fuel rail and gently wiggle it to break the seal.
• Expose the injectors by lifting off the fuel rail.
• The injectors are typically held in place with clips or retaining brackets, so carefully remove these fixtures without damaging them for reuse.
• Be cautious of any residual fuel that may spill during this process.

Installing the New Injectors

• Ensure the new injectors are the correct specification for your vehicle and inspect them for any damage.
• Check that the O-rings are intact and properly lubricated to create a good seal and prevent fuel leaks.
• Carefully insert each injector into the fuel rail, ensuring they are properly seated.
• Reattach the retaining clips or brackets to secure the injectors in place.
• Align the fuel rail with the engine and press down gently but firmly to seat the injectors.
• Reinstall the bolts to secure the fuel rail, tightening them to the manufacturer's specifications using a torque wrench.

Post-Replacement Procedures

• Reconnect the battery by first attaching the positive cable to the positive terminal, then the negative cable to the negative terminal.
• Tighten the nuts with a wrench to ensure secure connections.
• Double-check all connections and seals before starting the engine.

Testing the New Injectors

• Start the engine and allow it to idle for a few minutes.
• Observe the engine's behaviour and listen for any unusual noises that might indicate a problem.
• Inspect the area around the injectors for any signs of fuel leaks, which could suggest a poor seal or improper installation.
• Take the vehicle for a short drive to assess its performance, paying attention to the engine's responsiveness, acceleration, and overall smoothness.

Remember to refer to your G20's manual for specific instructions and always exercise caution when working with the fuel system to ensure a safe replacement process.

Frequently asked questions