The 1275cc fuel delivery system uses a rear-mounted electric SU fuel pump that draws fuel from the tank through a copper main feed pipe running beneath the floor. The pump is secured to a mounting bracket by a strap, with a rubber grommet isolating it from vibration. The pump’s characteristic ticking sound, a rapid clicking when the ignition is first turned on, slowing to intermittent ticks as the carburettor float chambers fill, is a reassuring sign that the fuel system is functioning correctly. Silence from the pump area when the ignition is switched on indicates either a failed pump, a blown fuse, or a wiring fault.
Float Chambers Specification
From the pump, a copper pipe delivers fuel to the rear carburettor, with the front carburettor fed from a connecting pipe on the rear float chamber lid. Flexible hose sections at the pump connections isolate vibration and accommodate the slight movement of the pump on its rubber-mounted bracket. These flexible sections are a common failure point on older cars, the rubber perishes from inside, and fuel-resistant replacement hose should be used.
1275cc Fuel Pumps Overview
A solid-state electronic replacement pump is available as an alternative to the original mechanical SU unit. The electronic pump provides consistent fuel delivery without the mechanical wear points of the original, no contact points to pit, no diaphragm to fatigue, and no rollerball valves to clog. It fits in the original location using the existing mounting strap and connections.