How does one do a leak off test.

thanks guys,gonna see if i can sort out the problem

hi guys im charles from south africa

hi everybody i need help,my freelander td4 2005 model wont start,she will start if you pull start her or start her with quick start,diagnostic test said low fuel pressure,ive changed the lp pump and filter,she still doesnt want to start,she kicks over but wont start,once started she runs...