The 1500cc fuel delivery system is fundamentally different from the 1275cc. Instead of a rear-mounted electric pump, the 1500 uses a block-mounted mechanical AC Delco pump driven from the engine camshaft. The pump is secured to the block by two studs, with a spacer and gasket between the pump body and the block face. The cam lobe inside the engine pushes a lever on the pump body, which operates the pump diaphragm to draw fuel from the tank and push it under pressure to the carburettors.
Carburettor Specification
Two mechanical pump variants were used during 1500 production, distinguished by their stud length and spacer arrangement. The correct variant is determined by the engine number.
When fitting a replacement pump, the gasket and spacer must be installed in the correct order and orientation, an incorrectly fitted spacer can alter the pump lever geometry, reducing the diaphragm stroke and therefore the fuel delivery rate.
Fuel Lines
The 1500’s fuel line system is more complex than the 1275cc arrangement. An intermediate pipe section connects the pump to a fuel delivery pipe, which splits at the rear carburettor to serve both carburettors. Flexible hose sections with specific clips connect each rigid pipe section. Each component of the fuel line is a separate part, and when ordering, the complete routing should be understood before individual sections are specified.
Fuel Pump
A solid-state electronic fuel pump is available as an alternative to the mechanical unit, fitting in the original block-mounted position and eliminating the mechanical wear points of the original diaphragm pump.