FUEL PUMP TECH
A modern petrol, diesel, or hybrid car would be useless without a means of getting the fuel from its tank to the engine. While various ingenious methods have been employed throughout history, the established set-up on modern cars comprises a low-pressure lift pump within the fuel tank, which incorporates a float/sender unit for the fuel level gauge, and a high-pressure pump within the engine bay.
The low-pressure pump’s purpose is to lift the fuel from the tank and pass it through a filter (either a pump-mounted strainer and/or a renewable canister fitted to the fuel line) and into the engine bay. For traditional indirect/port injected petrol engines, in which the fuel injectors locate behind the inlet valves, relatively low pressures are sufficient.
Modern direct-injection diesel and petrol (GDI) vehicles obtain impressive strainer and/or a renewable canister fitted to the fuel line) and into the engine bay. For traditional indirect/port injected petrol engines, in which the fuel efficiency and low CO2 emissions by controlling the fuel atomisation extremely accurately. To achieve this, a high-pressure fuel pump is driven via either the timing belt, or the camshaft. As 2000 BAR is a typical output, any DIYer must be respectful of potentially lethal consequences resulting from slackening a high-pressure fuel line, especially with the engine running.
What goes wrong?
Driving style makes no difference to fuel pump life. Fuel quality, service history and correct maintenance procedures are more influential factors. Apart from entering the otherwise sealed fuel system to replace the filter, a DIYer has little reason to disturb the circuit, unless there is a fault. Most issues tend to result in a low-pressure fault and log an associated fault code within the engine management. As with any fault diagnostics exercise, start with the simplest explanation, before suspecting more complicated components. As CM emphasises regularly, solving a problem by replacing parts blindly undermines the whole point of DIY car maintenance being effective and economical. The situation is especially prevalent with high-pressure pumps. Due to the very low tolerances employed therein, they are high-value parts and so it is inadvisable to replace one unnecessarily.
To guide us through the bestpractice methods of on-car diagnosing and replacing fuel pumps, leading remanufacturer and fuel injection specialist, Carwood, provided a 2016 Skoda Octavia vRS 2.0-litre diesel and talked us
