Triumph TR5 Lucas Fuel Pump
This unit was not a wonderfully designed piece of engineering. It is based on a windscreen wiper motor and is required to operate continuously at a much higher speed. The increase raises its running temperature to a point where, in high ambient temperatures it is likely to vaporise the fuel as it enters the pump housing. The incoming fuel then takes on the role of a coolant for the pump. If the fuel temperature is raised too high it will vaporise. The pump has no resistance when pumping fuel so the motor overspeeds. This is the wailing tone the pump makes as the engine stops working. Keeping the pump cool and subsequently the fuel within it, is of primary importance. The solution is a cooling coil that fits around the fuel pump motor. It carries diverted split fuel from the pressure relief valve around the pump motor before returning it to the fuel tank. The fitment of a fuel pump cooling coil is strongly recommended. The Lucas pump is not compatible with unleaded fuels and must be run with a suitable fuel additive. Should Lucas pumps become available suitable for unleaded fuel, refer to web site (or our sales office) and suffixed part number.
An alternative to the Lucas pump / cooling coil combination is the Bosch type replacement pump. This is of more modern design and extremely reliable if installed correctly (it’s also a lot quieter and compatible with unleaded fuels.)