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6-Cylinder Fuel Injectors Replacement
 
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Pelican Technical Article:

6-Cylinder Fuel Injectors Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$300

Talent:

****

Tools:

Set of sockets, 8mm, 10mm, flathead screwdriver, E10 inverter Torx, 17mm wrench

Applicable Models:

Mercedes-Benz E320 (2003-05)

Parts Required:

Fuel Injectors, fuel injector O-rings

Hot Tip:

Work with a cool engine and relieve fuel system pressure

Performance Gain:

Clean and even flowing fuel injectors

Complementary Modification:

Replace with performance injectors

In the early '90's Mercedes Benz still used the older CIS (Continuous Injection System) on even their flagship cars. These injectors have poppet valves in them that only open when fuel pressure is above 55psi. They would clog and develop bad spray patterns or be completely plugged. Further development led to electronic fuel injectors. Electronic fuel injectors allow greater control over fuel volume and emissions. However, these can fail the same way as the early injectors.

W211 models with a 6-cylinder engine utilize a fuel injector per cylinder. Over time injectors can become restricted or fail electrically. If you have an injector giving you a problem, I suggest replacing them in sets. This way you maintain an even flow from all the injectors. If you are removing the fuel injectors to replace the intake manifold and you plan to reuse the fuel injectors, replace all the fuel injector sealing O-rings.

It's a good idea to relieve fuel system pressure before beginning. This will minimize the amount of fuel spilled. The best way to relieve fuel system pressure is to remove the fuel pump fuse and run the vehicle until the engine stalls. See our tech article on fuel pump testing for more information.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Disconnect the battery. See our tech article on battery replacing.

Working at the engine cover (red arrow), pull off the two front sir duct hoses (green arrows).
Figure 1

Working at the engine cover (red arrow), pull off the two front sir duct hoses (green arrows).

To detach the ducts, pull them straight off the engine cover / air filter housing.
Figure 2

To detach the ducts, pull them straight off the engine cover / air filter housing. Then pull the front of the duct out of the radiator support and remove the duct from the engine. Repeat this step for each duct.

Lift up and remove the front engine cover.
Figure 3

Lift up and remove the front engine cover.

Then, pull the engine cover / air filter housing straight up to remove it.
Figure 4

Then, pull the engine cover / air filter housing straight up to remove it. The cover is held on by four metal clips that grab onto rubber mounts, with the front two shown (red arrows). The rear of the cover has two as well. Once detached, remove the engine cover / air filter housing from the engine. Remove the mass air-flow sensor. See our tech article on mass air-flow sensor removing.

Working at the right side valve cover, pull the breather hose straight off the breather cover to remove it.
Figure 5

Working at the right side valve cover, pull the breather hose straight off the breather cover to remove it.

Working at the rear of the intake manifold, pull the breather hose junction out of the intake manifold.
Figure 6

Working at the rear of the intake manifold, pull the breather hose junction out of the intake manifold. Pull it straight up to remove it. Once up, pull the hard line (red arrow) out of the breather hose and lay it aside.

To access the fuel injectors, you will have to remove the vacuum line (green arrow) from the wiring harness housing (red arrow).
Figure 7

To access the fuel injectors, you will have to remove the vacuum line (green arrow) from the wiring harness housing (red arrow). Then disconnect the necessary electrical connectors and lift the wiring harness housing up slightly.

Pull the vacuum line (red arrow) up to remove it from the housing.
Figure 8

Pull the vacuum line (red arrow) up to remove it from the housing.

Working at the left rear of the intake manifold, remove the 8mm bracket nut (red arrow).
Figure 9

Working at the left rear of the intake manifold, remove the 8mm bracket nut (red arrow). Then slide the bracket away from the harness housing (inset).

Just behind the bracket, cut the zip tie (red arrow) securing the harness to the engine.
Figure 10

Just behind the bracket, cut the zip tie (red arrow) securing the harness to the engine.

Working at the right side valve cover, disconnect the ignition coil electrical connectors by pressing the release tabs and pulling them straight out (red arrows).
Figure 11

Working at the right side valve cover, disconnect the ignition coil electrical connectors by pressing the release tabs and pulling them straight out (red arrows). Then cut the zip tie (green arrow) securing the wiring harness to the coil.

Working at the right side valve cover, disconnect the fuel injector electrical connectors by squeezing the release tabs and pulling them straight off (red arrows).
Figure 12

Working at the right side valve cover, disconnect the fuel injector electrical connectors by squeezing the release tabs and pulling them straight off (red arrows). Then disconnect the electrical connector at the EGR system (green arrow). Once all the connectors have been disconnected, press the plastic tab (yellow arrow) toward the right side fender and lift the wiring harness housing up off the fuel rail.

Back at the right side of the engine, remove the fuel pressure test port cap (red arrow).
Figure 13

Back at the right side of the engine, remove the fuel pressure test port cap (red arrow). Then cover the port with a rag and press the Schrader valve down to relieve fuel pressure. Reinstall the cap once the pressure is relieved.

Working at the left side of the engine, use a 17mm line wrench and remove the fuel line at the fuel rail.
Figure 14

Working at the left side of the engine, use a 17mm line wrench and remove the fuel line at the fuel rail. Once removed, cover the line and fitting on the fuel rail with a rag to collect excess fuel.

Next, remove four E10 inverted Torx fuel rail fasteners (red arrows).
Figure 15

Next, remove four E10 inverted Torx fuel rail fasteners (red arrows).

Then pull the fuel rail straight up and out of the intake manifold.
Figure 16

Then pull the fuel rail straight up and out of the intake manifold. Be careful not to damage a fuel injector when removing. If O-rings are stuck, you can lightly lever (red arrow) the fuel rail up using a pry bar. I like to lever between the edge of the valve cover and the fuel rail. Spray lubricant around the O-rings and allow it to soak in. This will make removing much easier. If there is dirt in this area, remove it before spraying the lubricant. It is very important that you lever directly up and not at an angle, if you lever at an angle, the O-rings on the fuel injectors may stick inside the intake manifold.

Once the fuel rail is removed, inspect the fuel injectors.
Figure 17

Once the fuel rail is removed, inspect the fuel injectors. Check that all of the O-rings (yellow arrow) came out with the injectors. If they did not (green arrow), you will have to remove them from the intake manifold using a hook tool (red arrow).If any of the O-rings fall into the intake manifold, you will have to remove the intake manifold to retrieve them. Once retrieved, reinstall the O-ring and the plastic retaining disc. Use a 9mm socket and press the O-ring on with the plastic disc last.

To remove individual fuel injectors, remove the retaining clip (green arrow) by sliding it off the fuel rail using a flathead screwdriver.
Figure 18

To remove individual fuel injectors, remove the retaining clip (green arrow) by sliding it off the fuel rail using a flathead screwdriver. Then pull the fuel injector straight out of the fuel rail in the direction of the red arrow. When reinstalling fuel injectors, replace the sealing O-rings and be sure that the retaining clips are properly seated on the fuel injector before attempting to install them. Press the fuel injectors into the fuel rail until the retaining clips snap into place (yellow arrow). Then press the fuel rail with the injectors into the intake manifold until they are fully seated. Then install the fuel rail fasteners and tighten. Reassemble the remaining items and check that there are no fuel leaks.

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