We're going to remove the mystery and fear surrounding N54 fuel injector replacement.
The N54 engine is a very popular platform with enthusiasts because of the potential power that can be unlocked. The stock fuel system was designed by BMW to be overkill, and unlike other direct injection cars, you can still drive at highway speed with a high pressure fuel pump failure. While this is impressive, the N54 fuel system as a whole can be a trouble spot on aging cars. One of the most common failures with the N54 is fuel injectors.
N54 fuel injectors are a piezo-electric injector and have more in common with diesel injection than regular gas injectors. The reason for this is the piezo style injector uses a quartz crystal stack to control fuel flow vs a solenoids like most conventional injectors. This allows for a massive volume of fuel to be moved. The main failure on earlier injectors is clogs and foreign debris restricting flow. These injectors have a built-in filter which on earlier injectors is known to melt at high temperatures. Once the filter fails the injector can no longer function properly.
BMW redesigned these injectors numerous times to address these failures. While some vehicles are still warrantied to this date, many of these cars have received replacement injectors numerous times over the course of their service life. What is important to know, is the updated injectors cannot be mixed with original style injectors. Anything injector marked 10 or lower in the same cylinder bank will require all the injectors in the bank to be replaced.
FCP Euro currently sells an injector that BMW uses for warranty repair. The reason this injector exists is to reduce the cost of warranty repairs to the dealers before they are reimbursed for parts and labor by BMW and to reduce the number of failures reported. There are two numbers at this time that you can order which are 13538648937 or 13538616079. 13538648937 is associated with SIB 13 08 15 which is for the S63 engine. This injector originally received a material update which was an improved internal filter which should not melt like in early injectors. At the present both 13538648937 and 13538616079 are the same injector with the same material update. The only difference is a significant cost savings. We prefer to sell the lower cost and equal injector to save customers which cannot qualify for warranty a significant sum of our of pocket expense. We also have a detailed blog article about this if you would like more information via the link below:
Tools needed to complete this repair:
- 14mm flare wrench
- Injector puller tool set
- e-torx socket set
- ISTA or INPA
- OBDII to USB K+DCAN compatible cable
- 13538648937 or 13538616079 - Piezo GDI Fuel Injector (Index 12)
- 13537564751 or 13538651060 - Decoupling Element
This will vary based on the car you're working on but first step is to remove the cowl cover/air filter housing in order to gain access to the rear most injector feed line and injectors. In most cases this cowl will be in the way and prevent you from getting the hob complete. The cowl covers in most BMW's are held in with clips and expanding rivets. I recommend having tools on hand such as a flat head screw driver and expanding rivet pliers.
Now that the cowl cover is out of the way it's time to start removing components on the engine that are in the way. First, remove the ignition coil by pulling the lock tab up and pulling the connector out. Then pull the coil off the plug. I recommend removing all 6 at the same time. Also go ahead and disconnect the electrical connector on the fuel injector.
This next step you will need to do in thirds. Each injector is held down with a retainer bracket. The retainer bracket puts downward force on the injector and keeps it seated in the cylinder head. One retainer bracket is used per two injectors. This is why I say break it up into thirds. The retainer bracket is held in with an E10 socket. Once the bolt is loose use a magnetic pickup tool to easily grab the bolt and retainer bracket. At this point it's time to release the feed line from the high pressure fuel rail and the injector inlet. Use a 14mm open ended wrench, crowsfoot, or line wrench to release the nut. Please be careful as there is still pressure in the system. Use a rag to block off fuel spray at the fuel rail. Once the nuts are unthreaded completely remove the line as set off to the side. I recommend capping off the opening on the fuel rail to prevent foreign material from getting into the fuel system.
Before removing the injector take an air nozzle and clean any loose debris from inside the cylinder head where the fuel injector is seated. This will help prevent any sand or debris from falling into the engine when you remove the fuel injector. At this point you will be ready to remove the injector. I recommend the use of a small slide hammer to get this job done as the viton seal can make removal of the injector tough to do by hand. We use a Baum tool for this job which threads onto the injector inlet port. A few taps of the slide hammer easily removes the injector. It's worth the investment of the tool just for the convenience factor. Once the injector pops out prepare the new injector for installation.
A word of caution however is beware of injectors that are already loose. The only reason they would be loose is because they had been installed incorrectly previously. Based on our own research it seems many injectors under warranty were installed without the proper decoupling element. This is a problem as failure to install the decoupling element has been known to cause ovaling out of the injector hole in the cylinder head. If the injector is loose already and the decoupling element is missing you may have a problem. Inspect the cylinder head and the shape of the injector hole.
Before installing the new injector record the calibration numbers as you will need them later to perform a DME calibration for the new injectors. The top number on the injector is the energy calibration number and the lower number is the flow calibration number. After you record this number for the cylinder 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. At this point you can install the injector by placing it back in the cylinder head. It will bottom out on it's own. Don't worry about forcing to bottom out as when you reinstall the retaining clip the injector will bottom out. At this point reinstall the fuel feed line onto the injector and tighten the flare nut on the injector and the flare nut on the fuel feed line.
If you are replacing multiple injectors or all injectors repeat steps 2, 3, 4, 5, and 6 until you complete all injectors.
After installing the injectors replace the ignition coils and reinstall all electrical connectors. At this point you're ready to start the engine. It may take a moment for the engine to start after a long crank as the fuel system need to build pressure. Once it starts check for any fuel leaks. If there are no fuel leaks you're ready to perform a DME calibration for the new fuel injectors. You can use INPA, ISTA, or another scan tool which is capable of doing this type of work. Simply enter the required information into the tool enter the calibration numbers in the required format, and complete the calibration. At this point you are done and can put everything else under the hood back together. If you do not have the ability to perform the calibration you can drive the vehicle to a shop or dealer to have the calibration carried out. It is technically not harmful to the engine but what we can say for sure is the engine will not perform optimally until the calibration is complete.
Overall this is not a difficult job even though it may seem intimidating. It is much easier to remove the injectors with the proper puller tool and I highly recommend having one on hand to do this job.
Key torque specs for reassembly:
- Injector Retainer Bracket to cylinder head - 13 ± 2 Nm
- Feed line from injector to fuel rail - 23 ± 3 Nm (coat flare nuts threads with transmission fluid)