Sylvie Willis
The Mercedes-Benz W126 is a series of S-Class automobiles manufactured between 1979 and 1992. Fuel injectors deliver fuel into the air stream as it enters the combustion chamber. If your car is running poorly, the injector should be checked. Removing and replacing fuel injectors on a W126 involves several steps, including disconnecting the battery, relieving fuel rail pressure, removing electrical connections, and carefully lifting the fuel rails. It is important to ensure that the injector holders are free of grime and that the engine is clean before beginning the process.
How to Remove Fuel Injectors W126
| Characteristics | Values |
|---|---|
| Tools Required | 3/8 drive ratchet, extension, 10mm socket, 5mm allen socket, 12mm combination wrench, two 14mm combinations, 17mm combination wrench, sil-lube |
| Step 1 | Disconnect the battery to eliminate potential spark hazards during repairs |
| Step 2 | Relieve the fuel rail pressure via the Schrader valve |
| Step 3 | Remove each injector electrical connection |
| Step 4 | Remove the air cleaner box and tubes |
| Step 5 | Remove the 2 large 17mm fuel lines from the side of the fuel distributor |
| Step 6 | Pull off the air distribution tube from the hose that goes to the other side under the distributor and all 4 injector holders |
| Step 7 | Disconnect the fuel line from the fuel injector |
| Step 8 | Use the 5mm allen socket to remove the hold-down bolt on the injector clip |
| Step 9 | Tighten each injector clip down till you have all 4 back in, then start putting the injection lines back on the fuel injectors |
| Step 10 | Reconnect all the lines and vacuum tubes back on in reverse order |
| Step 11 | Reconnect any electrical connections then turn the key on for 30 seconds before starting |
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What You'll Learn
Disconnect the battery to eliminate potential spark hazards
Disconnecting the battery is a critical step when removing fuel injectors from your car. This simple action eliminates potential spark hazards, ensuring your safety and peace of mind during the process. It is a preventative measure that should not be overlooked.
To begin, locate the battery in your car. It is usually found in the engine bay, often towards the front of the vehicle. Once you have identified the battery, proceed to disconnect it. You will need to disconnect the negative terminal, which is typically marked with a '-' symbol or a black cover. Use a wrench or a pair of pliers to loosen the nut that holds the cable in place, and then carefully detach the cable from the terminal. Ensure that the cable does not touch any metal parts of the car, as this could lead to an accidental spark.
It is important to note that some modern cars may have a positive terminal disconnect, so be sure to consult your car's manual or seek advice from a qualified mechanic if you are unsure. Additionally, if your car has any advanced electronics or security systems, they may be affected by disconnecting the battery, so it is always a good idea to consult an expert or refer to your car's documentation before proceeding.
By disconnecting the battery, you eliminate the risk of sparks that could potentially ignite flammable vapors or fluids, such as gasoline or oil, commonly found in the engine bay. This simple step adds an extra layer of safety, protecting you and your vehicle from potential harm. It is always better to be cautious when working with any electrical system in your car, especially when it comes to the fuel system.
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Loosen the fuel lines at the distributor
Before removing the distributor cap, tag the lead to the cylinder used for timing and mark its position on the distributor body. It is almost always No. 1 cylinder, but on some cars, another cylinder is used. If you are having difficulty removing the fuel lines, try applying a penetrating oil to the threaded connectors to help loosen them. You can let the oil sit for a few hours or overnight to give it time to work. Fuel line pliers can also be helpful for removing threaded fuel lines. These pliers grip the fuel line and allow you to apply force to release the locking mechanism without damaging the line or connector.
If you are working with metal fuel lines, you can try using two wrenches to help loosen the connectors. Use one wrench to hold the fuel line in place and another to turn the connector counterclockwise to loosen it. Be patient when removing stuck fuel lines, as it can be time-consuming. Take your time and work carefully to avoid damaging the fuel system. If the fuel lines are damaged or corroded, it is a good idea to replace them while you have the fuel system apart. This will help ensure that the fuel system is functioning properly and prevent future issues.
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Remove the air distribution tube
To remove the air distribution tube, you will need to pull it off the hose that goes to the other side under the distributor and all four injector holders. Be warned that if you have never changed these out on your W126 before, the tubes and air distribution hoses will break into tiny pieces. You can replace all the rubber, including the ones for the idle control valve, for under $100.
Before you begin, it is recommended that you clean your car to make it less painful to work on. One method is to use a low-pressure "spot-free rinse" setting at a coin-operated car wash to move the gunk off the engine.
To begin the removal of the air distribution tube, first, remove the air cleaner box and tubes. Then, remove the two large 17mm fuel lines from the side of the fuel distributor. Next, pull off the air distribution tube from both the hose that goes to the other side under the distributor and all four injector holders.
After completing the removal, you can replace all the rubber, including the ones for the idle control valve.
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Disconnect the fuel line from the injector
Disconnecting the fuel line from the injector of a W126 can be a tricky process. It is important to proceed with caution as fuel leaks can be dangerous. Before beginning, ensure that you have the necessary tools and safety equipment, such as a fire extinguisher, and work outdoors in a well-ventilated area.
First, remove the air cleaner box and tubes. This will give you access to the fuel lines. Next, remove the two large 17mm fuel lines that are connected to the side of the fuel distributor. You may need to loosen the lines at the distributor to make it easier to manoeuvre around them. Once the fuel lines are loose, you can focus on the fuel cluster. Remove the metal line that runs from the pump to the filter to the accumulator, ensuring that all fittings are 17mm.
The under-hood lines are nylon hoses with rubber shielding, making them particularly difficult to remove. To do so, disconnect all of the fittings, which should also be 17mm. Then, remove the 10mm bolt that secures the holding bracket to the distributor. Place a rag or towel over the air intake to catch any shavings or debris.
Finally, once the fuel line is disconnected from the fuel injector, use a 5mm Allen socket to remove the hold-down bolt on the injector clip. This will complete the process of disconnecting the fuel line from the injector.
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Remove the injector electrical connection
To remove the injector electrical connection, you must first disconnect the battery to eliminate potential spark hazards during repairs. Next, relieve the fuel rail pressure via the Schrader valve located on the fuel rail. This will spit out fuel when the centre pin is pressed, so have a collection device ready to catch it.
Once the fuel pressure has been relieved, you can remove the injector electrical connection. The exact process for this will depend on your specific engine, so it is recommended to watch a YouTube video that demonstrates the process for your particular engine.
After removing the electrical connection, you can move on to removing the injector rail hold-down fasteners. There are usually four of these, one in each corner, holding the injector fuel rails to the intake manifold. Most 2004+ engines use 10mm fasteners, while pre-2004 engines typically have 7/16" heads.
Finally, carefully lift the fuel rails from the engine, front and rear, at the same time. Be prepared to collect any fuel that may still be in the rail, as it may drip.
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