OM 617 chain tensioner

[Lajodi]

Hi all experts here!

I have a 617.912 engine in a Land Rover. The engine does not run well and I am going through it step by step now with the help of all the knowledge on this forum. Having dismantled the chain tensioner (as part of renewing chain/aligning camshaft correctly to crankshaft) I cannot see how it matches the description; "take care opening the cap as the spring is under tension and will come out". Behind my chain tensioner cap was no spring, but taking out the whole tensioner it seems to function correctly and certainly has a spring in it as it can be compressed with mild force. I have read about the ratchet function but there does not seem to be any of that on mine... Niether can I find any obvious way of dismantling it further. Any ideas please?