BMW Cars 1999-06

Fuel Rail (Supply Manifold) & Injectors

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Removal & Installation



If possible, always replace fuel injectors with like units. Different manufacturers have been used for the fuel injectors, and though they function and test the same way their flow rate may vary slightly and the injectors should not be mixed on the same engine.


CAUTION
Because the fuel injection system develops significant fuel pressure, always inspect the injector O-rings and if equipped, the fuel rail feed line O-ring carefully. Whenever possible do not reuse the O-rings.

The O-rings must be replaced if they are:



Brittle
 
Cracked
 
Deformed
 
Compressed
 
Damaged, cracked cut or chafed
 

Always lubricate the injector O-rings and the fuel rail O-ring with fresh oil or petroleum jelly to ease assembly and to avoid chafing or damaging them.



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Fig. View of a typical BMW fuel injector's components

  1. Remove the upper intake manifold.
  2.  
  3. Disconnect the electrical connectors for the fuel injectors and place the harness aside, then remove the dampening valve vacuum hose at the front of the fuel rail.
  4.  
  5. The two hose clamps for the fuel rail return line are stamped to be tamper proof. To remove, use a locking pliers and attach then onto the clamp-s adjustment screw head securely. Turn the adjustment screw counterclockwise until the clamp is loosened. Loosen both clamps and slide to the middle of the fuel line.
  6.  
  7. Using a 12 mm line wrench, loosen the fuel rail feel line flare nut and once loose, slide the flare nut away from the fuel rail.
  8.  
  9. To avoid debris from entering the injector ports, If compressed air is available, using an air nozzle, and wearing eye protection, carefully spray compressed air around the base of the injectors. If excessive debris exists, spray the base of the injectors with an evaporating brake cleaner and spray again with compressed air. If compressed air is not available, spray the brake cleaner to clean as best as possible.
  10.  
  11. Using a 10 mm socket, short extension and a ratchet, remove the two fuel rail mounting bolts.
  12.  
  13. Use a clean shop towel folded over several times to form a small pad, and place on the corner of the valve cover. Then using a suitable and sturdy pry tool, slowly and carefully lift the fuel rail until the injectors are just removed from the manifold, then remove the fuel feed and fuel return lines away from the fuel rail and remove the entire assembly with the large vent hoses still attached and set aside.
  14.  

M20 Engine
  1. Properly relieve the residual fuel system pressure.
  2.  
  3. Remove the intake manifold support from the manifold and valve cover.
  4.  
  5. Disconnect the fuel injector electrical plug plate lead under the intake manifold.
  6.  
  7. Disconnect the two coolant temperature sensors. Pull up and remove the fuel injector electrical plug plate.
  8.  
  9. Remove the 4 mounting bolts and pull the fuel rail up and out of the intake manifold. Remove the fuel injectors from the fuel rail.
  10.  

To install:

  1. Check the O-rings on the injector and replace if necessary. Check that all the injectors are of like types. Lubricate the O-rings with fresh oil or petroleum jelly and install them on the fuel rail.
  2.  
  3. Install the fuel rail on the manifold and tighten the bolts to 6.5-8.0 ft. lbs. (9-11 Nm). Install the electrical plate and connectors.
  4.  
  5. Connect the temperature sensors and the fuel injector electrical plate. Install the intake manifold support and tighten the bolts to 15-17 ft. lbs. (20-24 Nm).
  6.  

M42 Engine
  1. Properly relieve the residual fuel system pressure.
  2.  
  3. Remove the upper section of the intake manifold.
  4.  
  5. Remove the electrical plug plate from the injectors. Disconnect the fuel lines from the fuel rail.
  6.  
  7. Remove the fuel rail mounting bolts and pull the fuel rail with injectors up and off. Remove the retainers and the injectors from the fuel rail.
  8.  



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Fig. Upper manifold retaining nuts and vacuum line-M42 engine



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Fig. These vacuum hoses must be secure when installing the manifold-M42 engine



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Fig. Fuel connections and mounting of the fuel rail-M42 engine

To install:

  1. Check the O-rings on the injector and replace if necessary. Check that all the injectors are of like types. Lubricate the O-rings with fresh oil or petroleum jelly and install them on the fuel rail.
  2.  
  3. Install the fuel rail on the lower manifold and tighten the bolts to 6.5-8.0 ft. lbs. (9-11 Nm). Connect the fuel lines. Install the electrical plug plate and the upper intake manifold.
  4.  

M44 Engine
  1. Properly relieve the residual fuel system pressure.
  2.  
  3. Remove the upper intake manifold. For specific details, refer to Section 3.
  4.  
  5. Detach the electrical connectors from the fuel injectors and place the harness aside, then remove the pressure regulator dampening valve vacuum hose at the front of the fuel rail.
  6.  
  7. The two hose clamps for the fuel rail return line are stamped to be tamper-proof. To remove, use a pair of locking pliers and attach them onto the clamp's adjustment screw head securely. Turn the adjustment screw counterclockwise until the clamp is loosened. Loosen both clamps and slide to the middle of the fuel line.
  8.  
  9. Using a 12mm line wrench, loosen the fuel rail feel line flare nut and once loose, slide the flare nut away from the fuel rail.
  10.  
  11. To avoid debris from entering the injector ports, If compressed air is available, using an air nozzle, and wearing eye protection, carefully spray compressed air around the base of the injectors. If excessive debris exists, spray the base of the injectors with an evaporating brake cleaner and spray again with compressed air. If compressed air is not available, spray the brake cleaner to clean as best as possible.
  12.  
  13. Using a 10mm socket, short extension and a ratchet, remove the two fuel rail mounting bolts.
  14.  
  15. Use a clean shop towel folded over several times to form a small pad, and place on the corner of the valve cover. Then using a suitable and sturdy prytool, slowly and carefully lift the fuel rail until the injectors are just removed from the manifold, then remove the fuel feed and fuel return lines away from the fuel rail and remove the entire assembly with the large vent hoses still attached and set aside.
  16.  
  17. Remove the fuel injector retaining clip from the fuel rail, then remove the injector from the fuel rail and remove the injector from the air vent hose.
  18.  



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Fig. Inspect the feed line O-ring and replace as necessary. Lubricate the O-ring with fresh oil or petroleum jelly before reassembly



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Fig. Using a line wrench helps to avoid rounding off a flare nut



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Fig. The fuel rail is held onto the manifold with two fasteners. A 10mm socket, extension and ratchet are used for this procedure



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Fig. Protect the valve cover with a soft protective cloth and carefully pry the injectors and fuel rail away from the manifold



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Fig. The injectors can be removed from the fuel rail once the assembly is lifted away from the intake manifold



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Fig. The injectors are held onto the fuel rail with a metal clip



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Fig. Remove the metal clip and . . .



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Fig. . . . then remove the injector. Lubricate the O-rings with fresh oil or petroleum jelly during reassembly

To install:

  1. The installation is in reverse order of removal noting the following items.
  2.  
  3. Inspect the injector O-rings and the fuel rail feed line O-ring carefully and replace as necessary. If possible do not reuse the
  4.  
  5. Lubricate the injector O-rings and the fuel rail O-ring with fresh oil or petroleum jelly before assembling them to avoid chafing or damaging the O-ring.
  6.  

M50, S50, M52 And S52 Engines
  1. Properly relieve the residual fuel system pressure.
  2.  
  3. Remove the ECM/DME control module housing cover screws on the right side of the firewall. Remove the rubber strips along the wire duct by pulling up. Remove the screws from the wire duct and pull it out. This will allow enough movement in the injector wires to remove the injector electrical plug plate.
  4.  
  5. Remove the oil filler cap and the valve cover trim. Remove the injector area cover.
  6.  
  7. Disconnect the fuel feed at the front of the fuel rail. Remove the two screws holding the injector electrical plug plate. Pull up and remove from the injectors.
  8.  
  9. Disconnect the fuel return line. Remove the two bolts holding the fuel rail and remove the fuel rail by pulling off with the injectors. Remove the injectors from the fuel rail.
  10.  



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Fig. Fuel feed hose connection to the fuel rail-M50 engine illustrated



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Fig. The fuel rail is on the right, the injector plug plate on the left as shown with the cover loosened showing the wiring. It is not necessary to uncover the wiring when removing the plug plate-M50 engine shown

To install:

  1. Check the O-rings on the injector and replace if necessary. Check that all the injectors are of like types. Lubricate the O-rings with fresh oil or petroleum jelly and install them on the fuel rail.
  2.  
  3. Install the fuel rail and tighten the bolts to 6.5-8.0 ft. lbs. (9-11 Nm). Connect the fuel lines. Install the electrical plug plate.
  4.  
  5. Install the fuel rail cover and the valve cover cladding with the oil filler cap. Install the wire duct and the rubber stripping.
  6.  

S14 Engine
  1. Properly relieve the residual fuel system pressure.
  2.  
  3. Remove the bolts from the fuel rail. Disconnect the throttle switch electrical plug.
  4.  
  5. Pull up and remove the fuel injector electrical plug plate.
  6.  
  7. Disconnect the fuel lines and pressure regulator vacuum hose.
  8.  
  9. Pull the fuel rail up and out of the intake manifold. Remove the fuel injectors from the fuel rail.
  10.  

To install:

  1. Check the O-rings on the injector and replace if necessary. Check that all the injectors are of like types. Lubricate the O-rings with fresh oil or petroleum jelly and install them on the fuel rail.
  2.  
  3. Install the fuel rail on the manifold and tighten the bolts to 6.5-8.0 ft. lbs. (9-11 Nm). Install the electrical plate and connectors.
  4.  

Testing



The fuel injectors are an electro-mechanical device comprised of two interrelated systems, one being mechanical, the other electronic. The injector has two electrical terminals, one which receives a constant battery voltage when the ignition is switched to the ON position. The injector is triggered by a pulsating ground signal from the ECM/DME control module. The rate and the amount of time that the control module supplies the ground signal occurs in milliseconds, thus because the fuel supply and pressure for the injector is relatively constant by virtue of the fuel regulator, the fuel mixture is basically controlled by the length of time the injector is opened.

The mechanical portion of the injector is comprised of a small needle and its seat. When the injector is triggered by the electrical voltage, the needle is lifted of its seat and fuel is sprayed through its outlet nozzle. If debris is allowed to enter the injector, the needle can fail to properly seal against the seat and cause the injector to leak fuel when it is not being triggered, causing a rich running condition.

If debris enters the injector's spray nozzle, or if the spray nozzle is develops an accumulation of carbon particles, the spray pattern of the injector can be affected causing a lean running condition. A significant build up of carbon on an intake valve or the injector can also act like a sponge, which will absorb the fuel spray, also causing a lean running condition.

Because the injectors can be affected by an accumulation of deposits, BMW offers a fuel system additive that can be used to help keep them free of deposits and it's a good recommendation to use the additive at least once a year.


WARNING
When using a fuel additive, follow the manufacturer's recommendations. Most additives are added to a full tank of fuel. Using an additive with an insufficient fuel level could damage the low fuel indicator sensor or other related fuel injection components.

If a lean or rich running condition exists, most likely the check engine light will be activated. When attempting to diagnose a rich or lean running condition, a good start is to remove and examine the spark plugs from each cylinder. Remove the plugs keeping them in order for each cylinder. When reinstalling the spark plugs, replace any plugs that have built up deposits, have become fuel fouled or damaged. If all of the spark plugs exhibit the same appearance, the running problem could also be related to one of the following:



Defective fuel pressure regulator
 
A restricted fuel filter or fuel line
 
A poor electrical contact or poor ground
 
Defective or disconnected oxygen sensor
 
Defective engine coolant or air temperature sensor
 
The fuel delivery system such as a low fuel pump output
 

If the spark plugs differ in their appearance, this may be an indication as to which injector may be malfunctioning.

There are companies that specialize in fuel injectors and using specific test equipment, the can flow test the injectors and may be able to flush them of deposits.

Audible Check

The injectors make an audible "clicking" noise as they are activated by the electrical pulses. Check for an audible "clicking" noise as follows:

  1. If necessary remove any trim covers surrounding the fuel injectors.
  2.  
  3. Place the transmission in Park (automatic) or Neutral (manual), set the parking brake and block the road wheels to prevent the vehicle from moving.
  4.  
  5. Start the engine.
  6.  
  7. Using a stethoscope or a long shank screwdriver with a composite handle, check each injector for a clicking noise. If using a suitable screwdriver, place the end of the shank onto the injector and carefully place the composite handle against your ear. A clicking noise should be heard. If a clicking noise is not heard, perform an electrical check of the injector's wiring, and if possible, check the resistance of the injector.
  8.  
  9. Repeat the above procedure for each injector.
  10.  

Cylinder Drop Method

The injectors make an audible "clicking" noise as they are activated by the electrical pulses. Check for an audible "clicking" noise as follows:

  1. If necessary remove any trim covers surrounding the fuel injector electrical connectors.
  2.  
  3. If necessary remove any trim covers surrounding the fuel injectors.
  4.  
  5. Place the transmission in Park (automatic) or Neutral (manual), set the parking brake and block the road wheels to prevent the vehicle from moving.
  6.  
  7. Start the engine.
  8.  
  9. Unplug the fuel injector electrical connectors, one injector at a time. When the connector is removed the engine idle speed should drop.
  10.  
  11. Repeat this procedure for each injector and note the amount the engine's idle speed drops. If the idle speed does not change when the injector's electrical connector is removed, check the voltage signal for the injector. If a voltage signal is present, check the injector and replace as necessary. If the injector is not found to be defective, check that cylinder's spark plug color to determine if the cylinder misfire is caused by insufficient or excessive fuel. If necessary check the ignition system operation.
  12.  

Resistance Check

WARNING
When performing a resistance check of the injector circuit, a digital ohmmeter should must be used to avoid component damage.

  1. Turn the ignition switch to the OFF position.
  2.  
  3. Remove any trim panels or components necessary to access the fuel injector's electrical connector.
  4.  
  5. Label and detach the injector's electrical connector.
  6.  
  7. Using an ohmmeter with suitable probes, probe the two electrical connectors of the injector. The injector should have continuity. If the ohmmeter indicates an open circuit, the injector must be replaced. Although the factory does not supply resistance values for their injectors, during our teardown when checked, the measured injector resistance was 16.4 ohms.
  8.  



Click image to see an enlarged view

Fig. Using a suitable set of jumper leads allows an inaccessible injector to be checked

Voltage Checks
Voltmeter

CAUTION
When performing a voltage check of the injector circuit, a digital voltmeter must be used. Otherwise the ECM/DME control module could be damaged.

  1. Remove any trim panels or components necessary to access the fuel injector's electrical connector.
  2.  
  3. Turn the ignition switch to the OFF position.
  4.  
  5. Using a digital voltmeter, if possible, install a suitable set of jumper leads into the injector's electrical connector, or carefully back probe the connector.
  6.  
  7. Turn the ignition switch to the ON position and attempt to start the vehicle by engaging the starter motor and check for a pulsating voltage signal.
  8.  
  9. Repeat the above procedure for each injector.
  10.  
  11. If a pulsating voltage signal is not present:
    1. Leave the ignition switch in the ON position.
    2.  
    3. Attach one lead of the digital voltmeter to a known good ground and check for battery voltage at one of the injectors electrical connector's terminals for each injector. If:

      Battery voltage is not present, check the main relay and wiring to the injectors.
       
      Battery voltage is present, check the ground signal wiring between the injector's connector and the ECM/DME control unit.
       

    4.  

  12.  



Click image to see an enlarged view

Fig. A piggy-backed set of jumper leads allows the engine to run while the injector's electrical circuit is tested

 
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