That pump technology was abandoned by the manufacturers, but the mechanical pumps are not abandoned by the owners of the cars which are using them to ‘feed’ their carburetors.
The replacement of the carburetors with modern fuel injection systems which work more efficiently in higher pressures, made the usage of electric pumps eminent, because they can provide higher pressure fuel injection (3-4 bars) than the similar mechanical( 0.7 – 1 bars).
The mechanical pumps are installed within the engine block or within the cylinder head, driven from the crankshaft or the camshaft, respectively. They operate with a diaphragm, therefore characterized as ‘positive displacement’ pumps. The cam moves the pump lever and the lever moves the diaphragm, increasing the space of the chamber inside the pump resulting in fuel absorb. One way valves make sure the fuel flow goes only towards the carburetor.
A common problem is the rip of the diaphragm which results in fuel leak and low fuel pressure.
A significant difference between the mechanical and the electric fuel pumps is the fact that the mechanical, create lower pressure that draws fuel from the fuel tank while the electric ‘push’ the fuel from the tank to the engine.Therefore they are much safer than the electrics. Any leaks in the fuel line are easier to trace when there is an electric pump, but definitely more dangerous because the fuel line has high pressure and it will leak in bigger quantities.
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