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SAE J347: Diesel Fuel Injector Assembly Type 7 (9.5 mm) Standard
Overview of SAE J347 🛠️
SAE J347 is a surface vehicle standard that specifies the dimensional requirements necessary for the mounting and interchangeability of a clamp-mounted fuel injector used in diesel engines. It covers type 7 injectors with a nominal 9.5 mm holder shank diameter and focuses solely on the interface between the injector and the engine. The internal construction of the fuel injector remains optional with the manufacturer. First issued in 1968, the standard was reaffirmed several times before being cancelled in November 2015 and superseded by ISO 2698.
Key Dimensional Requirements
The standard defines critical interface dimensions to ensure that injectors from different suppliers fit the same engine bore. The following table summarizes what is specified and what remains optional:
| Aspect | Specification |
|---|---|
| Holder Shank Diameter | 9.5 mm (nominal) |
| Shank Length (L) | Defined in Figure 1 of the standard |
| Engine Bore Details | Defined in Figure 2 (includes diameter, depth, etc.) |
| Fuel Inlet & Leak-Off Connections | Optional; not specified |
| Method of Hold-Down | Optional; not specified |
| Internal Injector Design | Optional; left to manufacturer discretion |
🔍 Engineering insight: By standardizing only the mounting interface, SAE J347 enabled interchangeability across engine brands while granting manufacturers full flexibility in the internal design of the nozzle holder. This approach reduced development lead times and simplified supply chains for engine builders.
Cancellation and Supersession by ISO 2698
Standard Cancellation Notice
SAE J347 was cancelled in November 2015 and has been superseded by ISO 2698. The SAE Technical Standards Board determined that the content of J347 is fully covered by the ISO standard, making the SAE document redundant. All new designs and procurement should reference ISO 2698 directly.
Engineers and specifiers are advised to transition to ISO 2698 to ensure compliance with current international requirements. The two standards are technically equivalent, so existing applications using J347 dimensions remain compatible.
Frequently Asked Questions
1. What is the exact scope of SAE J347?
SAE J347 covers only the mounting interface for a clamp-mounted diesel fuel injector type 7 with a 9.5 mm holder shank. It specifies the shank length and engine bore dimensions but leaves fuel inlet, leak-off connections, hold-down method, and internal injector design unspecified.
2. Why was SAE J347 cancelled?
The standard was cancelled in 2015 because its content is fully covered by ISO 2698. To eliminate redundancy and conflicting references, SAE declared the document obsolete and superseded by the international standard.
3. Can I still use SAE J347 for new designs?
It is not recommended. The standard is cancelled and considered outdated. For current design and procurement, refer to ISO 2698. However, existing products built to J347 are still compliant as the dimensions are equivalent to the ISO version.
⚠️ Common Pitfall
Do not rely on SAE J347 for new engine designs or injector specifications. Using a cancelled standard can lead to non-conformance with current industry expectations. Also avoid assuming that the standard covers more than the mounting interface—internal design and leak-off arrangement are not specified and may vary between manufacturers.
