Hello,
Does anyone know what this sound might be? I had to change an injector, so I took this chance to remove all my injectors and clean all the dirt and grime on them, but now when I prep the fuel pumps, it does this weird squeaky noise. I haven’t seen anything leak tho.

 

The squeak is likely air trapped in the fuel system, or the pump working harder after reinstalling the injectors. If there are no leaks and the engine runs normally, it’s harmless and should stop once the system is fully pressurized.