The fuel delivery system changed three times during the Midget's production life: a mechanical AC-type pump on the earliest cars, an electric SU pump introduced from the Mk2 onward, and a different mechanical pump arrangement on the Triumph-engined 1500. The pump type, mounting location, and fuel line routing differ in each case.
948cc and Early 1098cc Mechanical Pump
The earliest Midgets fitted with the 948cc engine, and the early 1098cc Mk1 cars, used a mechanical AC-type fuel pump driven from the engine camshaft and mounted on the side of the block. This pump arrangement is shared with the contemporary Austin-Healey Sprite of the same period and the Morris Minor.
Replacement mechanical pumps for these earliest cars are available, and where the original block has been retained but a later electric pump is to be fitted, a blanking plate is required to seal the original mechanical pump aperture.
1275cc Electric SU Pump
From the Mk2 onward, an electric SU fuel pump replaced the mechanical arrangement, mounted in the rear of the car ahead of the fuel tank and isolated from the body by rubber grommets. This pump configuration was carried over into the 1275cc Mk3 and remained in use throughout 1275cc production. The pump is secured to a bracket by a strap, with rubber grommets isolating it from chassis vibration and a separate breather hose system routed through grommets in the boot floor. Fuel is drawn from the tank through a copper main feed pipe running beneath the floor, supported by clips along the chassis rail.
From the pump, a copper pipe delivers fuel forward to the carburettors, with flexible hose sections at the pump connections.
SU Pump Replacement Options
The original SU pump can be replaced with either a new traditional points-type SU unit, a reproduction equivalent, or a modern solid-state electronic pump that fits in the original location. The solid-state version offers improved reliability and consistent fuel delivery without the points wear and characteristic ticking of the original mechanical SU. A performance pump offering higher flow rates is also available for cars with modified engines requiring greater fuel delivery.
1500 Mechanical Fuel Pump
The 1500 reverted to a mechanical fuel pump, this time of Triumph design, mounted on the side of the block and driven from the engine camshaft. The pump is secured to the block by two studs, with a spacer and gasket between pump and block. The earlier pump type and the later replacement differ in their stud length and spacer arrangement, and the correct combination must be specified when ordering. The fuel line system on the 1500 is more complex than the 1275cc, with an intermediate pipe section, connecting hoses with specific clips, and a carburettor feed pipe that splits to serve both carburettors. Each section of the fuel line is a separate component.
Fuel Lines
Complete copper fuel line kits are available for both the 1275cc and 1500cc, providing all the hard pipe sections needed for a full fuel line renewal. These kits are pre-formed to the correct bends and lengths, making installation straightforward. Renewing the complete fuel line set is recommended during any restoration, as the original copper pipes can develop fatigue cracks at bending points, particularly where they are routed over or around chassis members and suspension components.
Fuel Ancillaries and Safety
In-line fuel filters, fuel hose in various bore sizes, fuel regulators, and stainless steel braided fuel hose are available as ancillary items. A fuel cut-off kit provides an additional safety measure by allowing the fuel supply to be shut off in an emergency, particularly valuable on cars used for competition or stored for extended periods. An in-line fuel filter fitted between the pump and carburettors will catch any tank sediment or pipe debris before it reaches the carburettor jets, preventing the running issues caused by partial blockage.