Overview
ISO 21042:2018 provides dimensional and tolerance guidance for the installation and integration of the high-pressure fuel pump in gasoline direct injection (GDI) engines. The standard focuses on the engine-side flange interface and mounting characteristics required for robust, repeatable assembly. It does not prescribe the external pump housing shape or the precise location of fuel connections, which vary by pump supplier and application.
Why this matters: correct flange dimensions, bolt patterns and connector compatibility reduce integration risk, improve interchangeability between suppliers and simplify service and assembly procedures.
Key Topics
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Engine flange interface and tolerances
- Preferred bore and mounting details include D1 = 35H7 and options for D2 = 32H7 or 26H7 where applicable.
- Bolt size: preferred M8 (M6 optional) and common mounting pitch values (e.g., 66 mm preferred; alternatives listed).
- Bore depth and effective screw depth: minimum bore depth values are given (e.g., 12 mm min.), and a practical minimum effective screw depth of around 15 mm is recommended to match material quality and bolt size-final values to be agreed between pump supplier and engine manufacturer.
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Pump intrusion / height and guiding
- The document addresses the pump intrusion (lower housing height) and guiding cylinder for the tappet to ensure correct mechanical engagement with the camshaft lobe.
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Low-pressure connector requirements
- Low-pressure inlet tube diameters: 8 mm (5/16") or 9.5 mm (3/8").
- Connectors shall comply with ISO 13948-2:2016 (type C) or SAE J2044. If SAE J2044 is used, bead radii must avoid sharp edges and ensure a minimum 0.25 mm annular flat for the female connector.
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High-pressure connector requirements
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Lubrication on assembly
- Ensure the pump plunger and tappet are supplied with lube oil during assembly. If assembled top-down, provide a drain or evacuation feature to remove oil and debris.
Applications
- Engine designers integrating a cam-driven high-pressure pump into cylinder heads.
- Pump suppliers preparing mounting interfaces for OEM engines to achieve interchangeability.
- Manufacturing and service teams needing clear dimensional references for assembly, inspection and maintenance.
Practical benefits: reduced rework at prototype and production stages, improved parts interchangeability, and clearer supplier–OEM agreements on interface design.
Related Standards
- ISO 18418-1 - Medium pressure fuel supply connections (GDI)
- ISO 2974 - 60° female cones for high-pressure injection components
- ISO 13948-2:2016 - Low-pressure (push-on) connections
- SAE J2044 - Quick connect coupling for liquid fuel systems
- ISO 18418-2 and ISO 19724 - related fuel system assembly and cleanliness guidance
For implementation, refer to the full ISO 21042:2018 document and coordinate final dimensions and material suitability between pump suppliers and engine manufacturers.