Trouble description: Main engine fuel injector pressure testing machine not working well. Yesterday I tested

Trouble description: Main engine fuel injector pressure testing machine not working well.

Yesterday I tested some valves and it was working. But today I checked the first valve and pressure is not going above 29 bar in the display.

Measures taken: Checked air side including pressure gauge, regulating valve.. all found Ok and I am able to increase pressure to 6.5 bar.

Parameters (Normal/Present): 450 bar / 29 bar

Present Status: There is a loud braying sound when I try to increase air pressure. The pump is continuously pumping fast and oil is gushing out of the recirculation outlet.