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This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 34, Propulsion, powertrain and powertrain fluids.

This second edition cancels and replaces the first edition (ISO 21042:2018), which has been technically revised.

The main changes are as follows:

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The motor vehicle industry is increasingly being pressured by the world's regulators to improve fuel consumption whilst reducing exhaust emissions (particularly CO2 emissions). The challenge for automotive engineers is to balance the trade-offs between the technology to improve fuel consumption and that to reduce regulated emissions.

One such engine technology is the direct injection spark ignition engine also known as the gasoline direct injection (GDI) engine. Listed amongst the advantages of GDI are a significantly improved fuel economy and corresponding lower CO2 emissions than on comparable gasoline engines.

With this technology comes new fuel system components and new interfaces with the engine. One component of the GDI fuel system is the high-pressure fuel pump that supplies fuel to the common rail. This high-pressure fuel pump is usually driven by a separate cam lobe on the engine camshaft and is thus integrated into the engine housing.

This document provides design engineers with best practices (dimensional requirements) for the assembly of the GDI fuel pump into the engine.

GDI fuel systems typically operate in a pressure range of around 35 MPa and are labelled “high-pressure”. In the context of all injection systems, including diesel, this same pressure range is considered as medium pressure, as diesel injection operates at much higher pressures.