You'll have to take a look and see. It is located on the engine side of the injection pump. 17mm bolt with banjo fitting and fuel line running back to the filter housing. If it has another smaller bolt head on the tip end of the valve that is where you open it up to get at the spring.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"