Why is my fuel pressure gauge shacking?

Hi guys i just tried a electric fuel pump on my old 318 now i have a stroked 426 from hughes and i used this pump http://www.racepumps.com/tech.html, the first time when i start my engine i adjust the fuel pump regulator at 7psi and it worked well then the gromet from my old gauge was damage and i loss fluid now i have a new gauge from russel but as you can see it dont show me the real pressure i will try to clean this stuff first and will let you knew what i find out thx Peter