If that's the case it all sounds very normal. Even on my 200K+ tensioner the cap is hard to put on with the spring's resistance. I thought the same thing first time I put mine back in. I even took it out and counted the total detents it could go thinking that with that pressure it surely must be going all the way in. But after wrestling with the cap and getting it tight I only counted about 5 or 6 clicks if I remember correctly.
Remember to take it apart and lubricate it and reassemble it EVERY time you take it out.