the faulty timing chain tensioner
 

Suppose i got two timing chain tensioners in my hands and one of the two im told that is a faulty one, how can i tell which one it is?

You can't. Spring tension variable, which design? You've got two light bulbs in your hand, which one will burn out first.

No i mean if there is actually some way in understanding if a faulty one is actually faulty or the tech is playing games with me.

You can't really tell by looking. Is the spring tension correct, is there something else in the system not to standards. If there is the slightest doubt the best course is to replace it, then you know. The cost of finding out the hard way far exceeds the cost of replacement. It wouldn't hurt to get a second hands on opinion either.

are they both same length? the new design is slightly longer than the original.

I think the actual fault was with the solenoid thing that actually keeps the tension on the tensioner no? Even though the actual guides pay the price, isnt it not their direct fault? Been a while since I dealt with it.

There are two designs of tensioner, the longer of the two is the updated and only one available.

You can tell a weak tensioner from a new one, many of the tensioners that come out when we do a timing cassette are weak enough to be compressed easily with a couple fingers, whereas a new tensioner will require both hands to compress.