Fuel Pumps

Fuel Pumps Explained

The fuel pump is a critical component in the combustion process, it's job explained in a nutshell is to provide petrol / diesel to the engine, but there's a lot more to it than that.

There are two types of fuel pumps, mechanical or electric.

Mechanical fuel pumps are driven by the camshaft, or by a special shaft driven by the crankshaft. The way in which this pump works is via its own cam lobe, and is remarkably similar to the internal combustion process just without the ignition. When fuel enters the pump the cam lobe is at its peak, opening the internals via an actuating lever that follows the cam surface, this lever pulls down a internal centre diaphragm to allow the maximum volume of fuel inside, when the inlet value seals and all the fuel is inside, the internal fuel is pressurised by the cam lobe being at its lowest and the actuating level returning to its resting state forcing the fuel out of the exit valve.

Electrical fuel Pumps are remarkably similar to mechanical ones apart from the camshaft being replaced with a solenoid / electromagnet. The electromagnet pulls an iron rod back which in turns pulls the diaphragm open allowing the maximum fuel inside, when the rod & diaphragm are at their peak of travel, all fuel is onboard, and inlet valve is closed the rod forces open a set of contacts breaking the current to the electromagnet and relaxing the pull on the diaphragm, which in turn pressurises and forces fuel out of the exit value.