The shutoff valve seems logical and for sure the pressure relief spring will be checked. Can you have sufficient volume but not enough pressure? I don't think it's anywhere close to 14 pounds. Last time I plugged the return line on my other 126 it blew the line off and I got a diesel bath. This one can be plugged with my finger and no fuel will get by with little pressure and no clamp on the return line(new hose).