Replacing Fuel Injectors In Your Classic Bmw 381 I

Changing the fuel injectors in a 1984 381i BMW is a complex process that requires specific tools and knowledge of car mechanics. The first step is to relieve the fuel system pressure and disconnect the fuel rail pressure testing cap, placing a rag underneath to absorb any spilled fuel. Next, the fuel supply line must be released by pressing the plastic collar and sliding the fuel line off the fuel rail. The fuel injector harness strip can then be released using a flathead screwdriver. After this, the four fuel rail fasteners can be removed, and the fuel rail pulled straight up and out of the cylinder head. To remove individual fuel injectors, the retaining clip must be slid off using a flathead screwdriver, and the injector pulled straight out. Before reinstalling, the sealing O-rings should be replaced and lubricated. The new injectors can then be installed, ensuring they are properly seated, and the fuel rail fasteners and injector retaining clips can be reattached. Finally, the fuel injector electrical connector must be reconnected, and any fuel leaks checked for.

Removing the engine cover and exposing the fuel injectors

To remove the engine cover and expose the fuel injectors of a 1984 BMW 381i, follow these steps:

First, grip the front of the engine cover and pull up to pop it off the front locating pins. Then, grab it by the right side and pull up to pop it off the last pin. For pre-2013 engines, there are also two vacuum lines on the passenger's side of the cover that need to be disconnected before you can remove the cover.

Next, remove the foam noise-reduction pad underneath the plastic engine cover. Simply pull up on it to remove it from the engine.

Now, move on to the engine cowl. Use a 10mm socket to rotate the fasteners at the back of the cowl by a quarter turn. Then, remove the plastic rivets securing the cowl near the fenders.

With the forward cowl pieces removed, the strut brace is exposed. To remove this, first, remove the two plugs from the rear cowl's center to reveal the strut brace's firewall mounting bolts. Then, pull the rubber strut covers off and remove the bolts with an E18 socket. Pull the brace out. To remove each strut cover, you will need to remove a plastic rivet.

After that, remove the cover that sits below the brace using a 10mm socket to remove its seven bolts.

Now, you can begin disconnecting the wiring from the cylinder head. Each cylinder has an ignition coil, a fuel injector, and a ground wire. Lift the locks on the ignition coils and unplug the harness from each of them. Then, pull up on the coils to remove them from the cylinder head.

Next, use an 8mm socket to remove the nuts that secure the two ground wires to the valve cover.

After that, disconnect the VANOS plug (the large round connector in the middle of the valve cover). To do this, push in on its two tabs and pull up. Then, use a flat-blade screwdriver to open the clip securing its wiring to the valve cover, and fold the plug and harness away from the engine.

Just beneath the VANOS plug is the high-pressure fuel pump. Disconnect it from the wiring harness too.

Finally, disconnect the fuel injectors. Space is tight here, so use a pick or a flathead screwdriver to pry back on the injector where the wiring harness plug connects. Prying on the injector will release the locking tab on the harness connector and allow you to pull it out.

With the engine cover removed and the fuel injectors exposed, you can now begin the process of removing the fuel injectors.

Disconnecting the wiring from the cylinder head

Step 1: Remove the Engine Cover and Expose the Fuel Injectors

Start by removing the engine cover to access the fuel injectors. On some models, you may need to disconnect vacuum lines from the engine cover. Once the cover is removed, you will see a foam noise-reduction pad underneath. Remove this pad to expose the engine further.

Step 2: Disconnect the Wiring from the Cylinder Head

Each cylinder has an ignition coil, a fuel injector, and a ground wire. To disconnect the wiring, follow these steps:

• Lift the locks on the ignition coils and unplug the harness from each of them.
• Remove the ignition coils by pulling them off the plugs.
• Disconnect the electrical connector on each fuel injector.
• Use a suitable socket (8mm or 10mm) to remove the nuts securing the ground wires to the valve cover.
• Disconnect the VANOS plug (the large round connector in the middle of the valve cover) by pushing in on its tabs and pulling it up.
• Open the clip securing the VANOS plug's wiring to the valve cover using a flat-blade screwdriver, and fold the plug and harness away from the engine.
• Disconnect the high-pressure fuel pump from the wiring harness.
• For the fuel injectors, use a pick or a flathead screwdriver to pry back on the injector where the wiring harness plug connects. Prying on the injector will release the locking tab, allowing you to pull out the connector.

Step 3: Remove the Fuel Injectors

Before proceeding, ensure you have a container or rag to catch any fuel spillage. Now, you can proceed with the following steps:

• Move a bracket off the back of the valve cover and remove its bolts.
• Disconnect the high-pressure fuel line from the pump to the rail, and then from the rail itself.
• Remove the high-pressure and low-pressure fuel lines from the engine.
• Loosen the fuel lines from the injectors.
• Remove the fuel rail by taking out the fasteners that mount it to the valve cover.
• Use an injector removal tool to remove the injectors. Place the tool onto the valve cover in the same orientation as the injector hold-downs.
• Thread the brass pieces of the injector removal tool through the girdle and into the tops of the injectors. The brass pieces are reverse-threaded, so be sure to leave them loose until the injectors are secured.
• Tighten the girdle to the valve cover, then use adjustable pliers or an adjustable wrench to back out the brass pieces, which will pull out the injectors.

By following these steps, you will successfully disconnect the wiring from the cylinder head and be ready to install the new fuel injectors.

Removing the fuel injectors

The following steps outline the process of removing the fuel injectors from a 1984 BMW 381i. This process will require some specific tools and parts, so it is important to gather everything before beginning. The tools needed include a flathead screwdriver, a set of sockets (10mm, 14mm, 17mm, 18mm), an injector removal tool, and a rag. The parts required are new fuel injectors and fuel injector O-rings.

Begin by relieving the fuel system pressure. Locate the fuel pressure test port cap and remove it, then place a rag under the port. Use a small flathead screwdriver to press the Schrader valve and release the fuel pressure. Ensure the rag is wrapped around the screwdriver to minimise fuel spillage.

Next, work at the centre of the fuel rail and remove the fuel supply line. To do this, press the plastic collar towards the fuel line and then slide the fuel line off the fuel rail. If the collar does not press in far enough, pull the fuel line towards the front of the vehicle, hold it in place, and then press and hold the collar while sliding the fuel line off. Place the disconnected fuel line on the valve cover, wrapped in a rag, to collect any excess fuel and keep dirt from entering the line.

Now, release the fuel injector harness strip from the fuel injectors. Use a large flathead screwdriver to gently pry up at each fuel injector to release the spring clips that hold the electrical harness. Be sure to lever straight up and keep the flathead next to the fuel injector connector you are releasing. Work your way down the injector electrical harness and disconnect each fuel injector.

Remove the four 10mm fuel rail fasteners and then pull the fuel rail straight up and out of the cylinder head. Be careful not to damage the fuel injectors during this step. If the O-rings are stuck, use a flathead screwdriver to gently pry the fuel rail up. It is recommended to pry between the edge of the valve intake manifold and the fuel rail.

To remove individual fuel injectors, slide off the retaining clip using a flathead screwdriver. Then, pull the fuel injector straight out of the fuel rail. If the injectors are difficult to remove, use silicone spray to lubricate the injector holes, which should help them slide out.

Tips for Reinstallation

When reinstalling the fuel injectors, it is important to replace the sealing O-rings before installing the new injectors. Lubricate the sealing O-rings with silicone grease that is safe for use on rubber to help the injectors slide into the cylinder head with ease.

Evenly press the fuel rail with injectors into the cylinder head, ensuring that all injectors are properly seated. Check that the mounting tabs are sitting flat on the cylinder head, then install the fuel rail fasteners and tighten them. Install the fuel injector retaining clips, ensuring they are fully engaged and sitting in the groove in the fuel injector, snapping onto the fuel rail. Reassemble the remaining items and check for any fuel leaks.

Installing the new fuel injectors

To install the new fuel injectors, you will need the following tools:

• Injector puller tool set
• Magnetic pick-up tool
• OBDII to USB K+DCAN compatible cable
• BMW Fuel Injector Removal Tool
• Scan tool

And the following parts:

• BMW N54 (Index 12) Fuel Injector Kit
• Decoupling elements
• Decoupling rings
• Fuel injector O-rings
• Fuel injector Teflon seals
• Steel fuel lines

Step 1: Remove Cowl, Rubber Gasket, and Engine Cover

Remove the cowl cover/air filter housing, which will give you access to the rearmost injector feed line and injectors. On most BMWs, the cowl cover is held in with clips and expanding rivets, so you will need tools such as a flat-head screwdriver and expanding rivet pliers.

Step 2: Disconnect and Remove Coil and Wiring Harness

Remove the ignition coil by pulling the lock tab up and the connector out. Then, pull the coil off the plug. It is recommended to remove all six at the same time. Also, disconnect the electrical connector on the fuel injector.

Step 3: Remove the Securing Bracket and High-Pressure Fuel Line

Remove the retaining bracket, which is held in with an E10 socket. Once the bolt is loose, use a magnetic pickup tool to grab the bolt and retainer bracket.

Use a 14mm open-ended wrench, crowsfoot, or line wrench to release the nut. Use a rag to block off fuel spray at the fuel rail. Once the nuts are removed, completely remove the line and set it off to the side. Cap off the opening on the fuel rail to prevent foreign material from getting into the fuel system.

Step 4: Remove the Injectors

Before removing the injector, use an air-gun nozzle to clean any loose debris from inside the cylinder head where the fuel injector is seated. This will prevent any sand or debris from falling into the engine when you remove the fuel injector.

You are now ready to remove the injector. A small slide hammer can be used to get this job done; the Viton seal can make removal of the injector tough to do by hand. A few taps of the slide hammer easily removes the injector. Once the injector pops out, prepare the new injector for installation.

Step 5: Record the Injector Calibration Numbers and Install New Injectors

Before installing the new injector, record the calibration numbers; you will need them later to perform a DME calibration for the new fuel injectors. The top number on the injector is the energy calibration number, and the lower number is the flow calibration number. After you record the number for the cylinder that the injector is being installed into, install a new decoupling element and remove the protective cap on the tip of the injector. The cap can be difficult to remove as it keeps the Viton seal compressed and the tip clean. Simply twist back and forth as you pull it off.

You are now ready to install the injector by placing it back into the cylinder head. Don't worry about forcing it to bottom out; when you reinstall the retaining clip, the injector will bottom out on its own. Reinstall the fuel feed line onto the injector, tighten the flare nut on the injector, and the flare nut on the fuel feed line.

Step 6: Reassembly and DME Calibration

After installing the injectors, reinstall the ignition coils, retaining bracket, and all the electrical connectors. Now you're ready to start the engine. It may take a moment for the engine to start after a long crank; the fuel system needs to build pressure. Once started, make sure to check for any fuel leaks. If there aren't any fuel leaks, you're ready to perform a DME calibration for the new fuel injectors. You can use INPA, ISTA, or another scan tool capable of DME calibration. Enter the required information into the tool, enter the calibration numbers in the required format, and complete the calibration.

Step 7: Final Steps

If you do not have the ability to perform the calibration, you can safely drive your car to a shop or dealer to have the calibration carried out for you. Technically, it's not harmful to the engine, but the engine will not perform optimally until the calibration is complete.

Reconnecting the electricals and coding the injectors

Now that you have installed the new injectors, it is time to reconnect the electricals and code the injectors.

First, flop the VANOS plug back over the valve cover and plug it in. Then, connect the injector connectors and the high-pressure fuel pump. Refit the ignition coils to the spark plug tubes and plug them in. Slide the ground wires over their studs and thread on the nut used to secure them. Use an 8mm socket to tighten the nuts.

Now everything concerning the engine should be reconnected unless your vehicle is pre-2013, in which case the two vacuum lines that run to the engine cover are still disconnected. Place the engine cover over the engine just to reconnect the lines if your car requires it. Then head into the cabin and break out the scan tool.

The high-end scan tool required for this job, like the MX808, can go into the engine computer and recode the injectors. Turn the ignition on and plug in the scan tool. Select the "service" option, and then select the "injectors" option. After that, select "BMW" and let the tool read the car's computer to get its VIN. Once it has the VIN, it'll bring up several parameters about the vehicle. Select "yes" and let the tool communicate with the engine computer. When it's done reading, select "Hot function" and then "Injection quantity compensation."

The tool will reread the computer and give you the previous codes for each of the old injectors. For the next two prompts, select "continue" and then "no." Now you'll have four options, and you need to choose the option "F4: Enter new adjustment values."

From here, enter which cylinder you're adjusting and then what the injector code for that cylinder is. Once you've entered the injector codes, save the new values and then start the vehicle.

Quickly get to the engine bay to check for any possible fuel leaks from all of the fittings. Shut the car down and fix any leaks that are present. If there aren't any leaks, continue to reassemble the engine bay.

Frequently asked questions