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Injector Fitting Instructions/Assembly Guide

Fuel suitability

ASNU injectors are designed for operation with gasoline based fuels up to E98, and are able to operate long term on fuels containing MTBE or ETBE. For other fuels such as Methanol-M100, please contact us to discuss suitability, as alternative seals and O-rings may be required.



It is necessary to lubricate both the upper and lower O-rings and any manifold seals before installation into both the engine and the fuel rail. We recommend the use of a clean, non-silicon based motor oil. Ensure the oil does not contaminate the internals of the injector or the spray plate assembly.


For certain turbocharged applications, the sealing tolerances for the injector to manifold/cylinder head have been changed to ensure a leak free installation at higher than stock boost levels where the OE seals can cause leaks.

If, during maintenance, the injectors are removed and are to be refitted, fresh O-rings should be used. Spare O-rings can be purchased from ASNU’s approved Distributors or Service Centres.


When fully assembled into a cold engine, the injector must be free to rotate around its’ axis with a small amount of longitudinal movement (0.5 to 1.5mm). This ensures that the injector is not damaged by over compression when thermal expansion of the injector and related engine components occurs. We advise checking your fuel rail manufacturer's instructions for compatibility with our injectors if you are not using an ASNU fuel rail.



A minimum filtration of 10 Microns is required for short term operation <3000 miles. For long term operation >3000 miles a filtration level of 5 Microns is advised. The life of the in-line fuel filter is to be determined by the user in response to environmental conditions and fuel quality. Failure to adhere to these limits may result in a drop in injector flow / performance and damage to the injector itself.


Service Life and Storage

To maintain the performance and tight operating tolerances of the injector, it is advised to send your injectors to ASNU Service Centres to check their operation and be cleaned if necessary. We recommend replacing the O-rings during their service.


Chemical cleaners may damage the injector and should not be used. Injectors that have been unused for some time such as with stored vehicles or spare parts should be checked before operation.

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