In the early days of motoring, fuel was fed by gravity from the tank to the carburettor. This worked satisfactorily with high bodywork and a side draft or updraft carburettor, and had the advantage of simplicity, although it was considered normal practice to switch the petrol off after stopping the engine, in case the needle valve stuck. Ford's Model T was notorious for suffereing from fuel starvation on steep hills with the under seat tank, if you were a bit low in fuel, and the last year of production and their Model A moved the tank to behind the instrument panel (a common location on many contemporary cars).
But lower bodywork, and a dawning concern for separating the petrol tank from the passenger compartment led to the tank in most cars moving to the rear of the vehicle by the early thirties. The issue then was how to get fuel to the carburettor. Early methods included pressurising the tank either with a hand pump or from the exhaust (or both), but this was replaced by the Vacuum tank, where an auxiliary tank of about two litres placed on the upper firewall behind the engine was filled automatically by manifold vacuum. This was an effective but expensive and not entirely trouble free solution.
The development of petrol resistant rubber by about 1930 made possible relatively cheap diaphragm fuel pumps. These took two tracks - mechanical ones and electrical ones.
Mechanical pumps were simpler and cheaper to make, but required substantial changes to the engine - changes to the crankcase casting, an eccentric on the camshaft etc. This meant that they tended to be used by manufacturers with high production numbers, especially in the US, where 6v electrical systems continued for longer.
Small scale manufacturers, including Rover, adopted electric pumps, as these required no changes to the engine, and presumably they were happy enough to continue not providing a place on the engine for a mechanical pump until the introduction of the 2.0 diesel in 1957, and this may have been because of the pressure and volume requirements for the diesel. This continued on with derivatives of that engine. The six, derived from a 1940 design, as was the 1.6 and 2.0 petrol engine, retained the electric pump.
In tank electric pumps were a much later development, the result of hot engine compartments packed tight that increasingly caused vapor lock issues.
John
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol
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