What's wrong?

Well, we wanted to test all of our ten fuel injectors but we did not trust the manometer.
The injector has to make a cracking sound while opening at appr 300 bar (4 351 psi) but each time we tested it cam not always back to zero so at last we decided to stop and order a new manometer.
The injector blows into the bucket.
We have to be careful because everything is in fresh paint....