Replacing Fuel Injectors: A Step-By-Step Guide For Your 2002 C240

If your 2002 Mercedes-Benz C240 is starting to run rough, getting horrible gas mileage, or displaying error codes, it may be time to replace the fuel injectors. This DIY maintenance guide will walk you through the process of changing the fuel injectors on your C240, so you can get your car running like new again.

Prepare the car for fuel injector replacement

Before you begin, make sure you have the right tools and parts for the job. For this task, you will need a Torx set and pliers, as well as new injectors and White Lithium grease.

First, you need to prep the car. Remove the fuse for the fuel pump and try to start the car. It will turn over and then die. Do this a few times to help drain excess fuel from the system. Also, open the gas cap to help depressurise the system.

Next, make sure the car has cooled down. You don't want to be working with gasoline when the car is hot. Have a fire extinguisher handy, as there will be some fuel spillage. Wear chemical-resistant gloves to avoid getting gasoline on your hands, and have plenty of paper towels or rags ready to help with the cleanup.

It's recommended that you perform the injector removal in a clear, open, and well-ventilated space. It may be a good idea to have an assistant around in case there are any problems.

Now, open the hood and remove the engine covers. First, remove the forward-most cover (the one with the star) by pulling it straight up. Next, remove the two plastic air intakes – they are both just friction fits and will pull off. Then, remove the main engine cover. There are four clips on it: two that you can see by the vacuum regulators and two underneath. Pull the cover straight up and off.

Remove the engine covers

To remove the engine covers of your 2002 C240, you'll first need to open the hood. You will then need to remove the forward-most cover, which has a star on it. This can be done by pulling it straight up. Next, you will need to separate and remove the two plastic air intakes, which are both friction fits and can be pulled off. Now, you can remove the main engine cover. There are four clips on it, two that you can see by the vacuum regulators, and two that are hidden underneath. Pull the cover straight up and off.

Disconnect the fuel rail

To disconnect the fuel rail on a 2002 C240, you will first need to prep the car. Remove the fuse for the fuel pump and attempt to start the car. Do this a few times to drain excess fuel from the system and open the gas cap to help depressurize the system.

Next, you will need to open the hood and remove the engine cover. There are four clips on it, two that you can see by the vacuum regulators, and two underneath. Pull the cover straight up and off.

Now, you will need to remove the larger rubber crossover hose between the vacuum regulators at the front of the engine, as well as the small rubber hose with a Y connector on the passenger side. Unclip the electrical connector by the driver's side vacuum regulator by squeezing the two metal ends together and pulling it off.

There is also a hard plastic line that runs along the top of the driver's side fuel rail that will need to be removed. This is for the EGR purge valve. Simply pull it out of its connectors and set it aside.

On the driver's side valve cover, there are two emission hoses that you will need to remove to give you more room to work. They just pull straight off. Check these as they can dry out and crack over the years.

Now, move to the passenger side and disconnect the single hose there.

If you are unsure how much fuel you drained from the system, you can open the Schrader valve at the end of the passenger side fuel rail to release more fuel. Make sure you have rags handy as there will be spillage.

Now you are ready to remove the four bolts holding the fuel rail and injectors in place. You will need an E10 female Torx socket for this. With everything loose, simply pull the rail and injectors up and out of the manifold. Be sure to put a few rags in the open holes in the manifold to prevent anything from falling into the engine.

• Have a fire extinguisher, chemical-resistant gloves, and plenty of rags or paper towels on hand.
• Perform the injector removal in a clear, open, and well-ventilated space.
• It may be helpful to have an assistant in case of any problems.
• Be extremely careful not to drop anything into the open holes in the manifold, as this can cause catastrophic damage.
• If you have had a severely leaking injector, it is a good idea to remove the coils and plugs to drain the combustion area of excess fuel.
• Make sure to disconnect the fuel pump fuse or relay before attempting any work on the fuel system.

Remove the fuel injectors

Before starting, ensure you have the right tools and parts for the job. For this task, you will need an E10 female Torx socket and a set of pliers. It is also recommended to have new injectors and white lithium grease.

Now, to remove the fuel injectors:

• Prep the car: Pull the fuse for the fuel pump and try to start the car. Do this a few times to help drain excess fuel from the system. Open the gas cap to help depressurise the system and allow the car to cool down.
• Safety first: Have a fire extinguisher, chemical-resistant gloves, and plenty of paper towels or rags on hand. Perform the injector removal in a clear, open, and well-ventilated space.
• Remove engine covers: Open the hood and remove the forward-most cover with the star on it by pulling it straight up. Then, remove the two plastic air intakes by pulling them off (they are friction fits). Finally, remove the main engine cover by pulling it straight up and off—it has four clips, two of which are visible by the vacuum regulators and two are underneath.
• Gain access to the fuel rail: First, remove the larger rubber crossover hose between the vacuum regulators at the front of the engine, along with the small rubber hose with a Y-connector on the passenger side. Next, unclip the electrical connector by the driver's side vacuum regulator by squeezing the two metal ends together and pulling it off. Then, remove the hard plastic line for the EGR purge valve that runs along the top of the driver's side fuel rail by pulling it out of its connectors and setting it aside. Finally, move to the driver's side and disconnect the two emission hoses on the valve cover—they just pull straight off. Check these, as they may need to be replaced.
• Remove the Torx bolts: Move to the passenger side and disconnect the single hose there. If you are unsure how much fuel you drained from the system, you can open the Schrader valve at the end of the passenger side fuel rail to release more fuel. Be sure to have rags handy to catch the spillage. Now, remove the four Torx bolts holding the rail and injectors in place using the E10 female Torx socket.
• Lift out the rail and injectors: With everything free, simply pull the rail and injectors up and out of the manifold. Be careful, as the injectors are just held in the manifold by O-rings and will pop out. Place a few rags in the open holes in the manifold to prevent anything from falling into the engine.
• Detach the electrical connector and metal clips: Remove the electrical connector on the injector by pushing in the two clips and pulling the connector off. Then, remove the metal clips holding the injectors to the rail—these can be pried or pulled off. Finally, wiggle the injector out of the rail, as it is now only held in place by the O-ring.

Install the new fuel injectors

Now that you have removed the old fuel injectors, it is time to install the new ones.

First, apply a small amount of White Lithium grease to the new O-rings that come with the injectors. Then, reinstall the injectors. The injectors are held onto the fuel rail by metal clips; you can pry or pull these off. Next, wiggle the injector out of the rail; it is just held in by the O-ring at this point.

Now, you can install the new injectors. Push the new injector into the fuel rail, ensuring that the O-ring is seated correctly. Then, push the metal clip back into place to hold the injector in the rail.

Finally, reconnect the electrical connector on the injector. It is a simple push-and-pull connector. Push in the two clips and pull off the connector.

Frequently asked questions