Manual - Chapter 5 - Fuel & Oil

17: Fuel system electrical components: removal, examination and refitting

Fuel injection relay

  1. This controls the supply of current to the various components of the system and can be tested only by substituting a new component. It is situated in the electrical components box under the rear of the fuel tank and is removed and refitted as described in Chapter 10.

Airflow meter

  1. This unit is situated in the top half of the air filter housing. Refer to Section 15 for details of removal and refitting.
  2. No information is available to assist the ordinary owner to test this component; in the event of a fault arising the machine should be taken to an authorised BMW dealer or similar expert for checking. Do not attempt to test it using self-powered test circuits or testing equipment: it may be seriously damaged by the application of incorrect voltages.
  3. If the unit is found to be faulty, it must be renewed; note that the mounting bracket is available separately if it has been cracked or otherwise damaged.
  4. The air temperature sensor situated in the meter intake is very sensitive and must not be disturbed; it can be renewed only as a part of the meter assembly.

Throttle position switch

  1. This component is mounted on the rear end of the throttle butterfly shaft. If it is to be removed, on K100 RT and K100 LT models, first detach the fairing left-hand knee pad to permit adequate working clearance.
  2. Disengage the retaining wire clip and unplug the connector, then unscrew the two retaining screws and withdraw the switch.
  3. On refitting, position the switch on the butterfly shaft and tighten the retaining screws lightly. Check the throttle cable adjustment and rotate the switch so that a distinct click is heard from it just as the throttle cable slack is taken up and the butterflies begin to open; hold the switch in that position and tighten the retaining screws securely. Refit the connector plug, ensuring that the wire clip locks securely into place.
  4. There is no information to assist the ordinary owner in testing this component; in the event of a fault arising the machine should be taken to an authorised BMW dealer tor checking. Do not attempt to test it using self-powered test circuits or testing equipment; it may be seriously damaged by the application of incorrect voltages.
  5. If the unit is found to be faulty, it must be renewed.

Fuel injection control unit

  1. 11 Unlock and raise the seat, then withdraw bath side panels. See Chapter 7. Withdraw the cover from the front storage tray, also any items contained in it.
  2. Gripping the tab at its front end, pull the black plastic cover sideways out of the control unit storage compartment.
  3. Inserting a slim-bladed screwdriver through the access hole in the floor of the storage tray, release the locking catch by pressing it to the rear, then unplug the control unit connector plug from the rear end first and pull it out to the side.
  4. The control unit is secured in its compartment by the rubber mountings on the left-hand side, and by a locking pin on the right-hand side; to extract the locking pin, grip its flattened end with a pair of pliers and pull it upwards. The control unit can be removed from the storage tray while it is in place on the machine. or the two can be removed together and separated, if necessary. Ensure that the rubber mountings are located securely in their grooves on reassembly, and check that the locking catch snaps back into place as the connector plug is refitted.
  5. The unit cover is retained by clips around its edge and by the two rubber mountings on the left-hand side. If the unit has become saturated with water it may be permissible to remove the cover to assist in drying out. but at all other times the cover must not be disturbed. If the unit is thought to be faulty, take the machine to an authorised BMW dealer tor expert attention. Do not undertake any form of testing or repair work with anything other than the BMW test equipment. If the unit is faulty, it must be renewed.
  6. The unit is extremely sensitive and must never be knocked, dropped or otherwise mishandled. Note that it can be upset even by tools or similarly heavy objects rattling around in the storage tray; any items carried in the tray should therefore be either very light in weight (as recommended by BMW) with all tools carried in the tail compartment, or they should be well-wrapped in thick cloth so that they cannot move or vibrate when the machine is in motion.


17.1 Location of fuel injection relay


17.5 Note air temperature sensor in mouth of airflow meter - do not disturb


17.6 Throttle position switch is situated on rear end of butterfly assembly - note adjusting screws (arrowed)


17.12 Removing fuel injection control unit - withdraw compartment cover as shown ...


17.13 ... then disconnect control unit connector plug


17.14a Control unit is retained by locking pin on right-hand side and by ...


17.14b ... rubber mountings on left - note that these also retain unit cover, but that the mounting shown is incorrectly fastened - always check that cover is secure