Land Rover Discovery Owners & Service Manuals

Land Rover Discovery: Misfueling protection device

Passive Misfueling Protection Device System

Passive Misfueling Protection Device System

  1. Filler neck
  2. Flap
  3. Reset slots
  4. Spigots
  5. Reset tool
  6. Spring

The passive misfueling protection device system comprises a mechanically operated flap which is triggered when the smaller diameter filler nozzle tube, used on petrol pumps, is inserted in the filler neck. The shut off flap is actuated and blocks the sensor port on the fuel pump nozzle, causing it to automatically switch off. The shut off flap is locked in this position by a latch mechanism, once it has been activated.

The tool is used to reset the misfueling protection device if triggered. The tool is inserted into the filler opening as far as possible with the spigots pointing upper most. Once the two spigots on the tool are located in the slots it can be pulled outwards, releasing a latch and allowing the shut off flap to be opened by its own spring pressure.

The shut off flap is colored yellow so that it is clearly visible within the entrance of the fuel filler pipe when activated, the shut off flap has a 'Handbook' symbol on it.

A 25 mm diameter diesel fuel pump nozzle will not activate the misfueling protection device because the nozzle stops against two molded lugs.

However, if a 21 mm diameter unleaded petrol pump nozzle is inserted into the housing, its smaller diameter allows it to pass the two molded lugs. The nozzle strikes two pins on the inside of the filler housing which move forward. This movement rotates the shut-off flap which is then held in place when the nozzle is removed by the latch mechanism.

Active Misfueling Protection Device System

Normal State

Normal State

  1. Sensing tabs in normal state
  2. Misfueling protection flap closed

Open State

Open State

  1. Sensing tabs in open state
  2. Misfueling protection flap open

The misfueling protection device consists of a mechanically-operated flap and three fuel nozzle sensing tabs. When a 25 mm diameter diesel fuel filler nozzle tube is inserted into the fuel filler pipe, the three sensing tabs depress releasing the flap into the open position. If a smaller 21 mm diameter filler nozzle tube, used on unleaded petrol pumps, is inserted in the fuel filler pipe, the three sensing tabs will not depress and the flap will not release, so this blocks the fuel nozzle from entering the filler pipe.

Adaptor Funnel

Adaptor Funnel

If the vehicle travels to a market where differentiation of fuel nozzle size or if the vehicle runs out of fuel and must be refilled at the road side using a reserve can, then an adaptor funnel is provided to allow the misfueling device to be temporarily overridden.

The adaptor funnel will be located either in the glovebox or in the luggage compartment alongside the tool kit.



  1. Coolant inlet connection
  2. Fuel inlet connection
  3. Coolant outlet connection
  4. Fuel outlet connection

The LP fuel cooler is located in the engine compartment. The fuel cooler is connected to the engine cooling system.

The fuel cooler is designed to cool fuel returning from the HP pump before it is sent back to the fuel tank via the return line.


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