96 SLS Fuel supply problem

4.6l Seville SLS No start, I have run pressure test on fuel line (56 psi) falls to about 10 psi in 10 min. Have done fuel relay bypass test to pressure up the fuel rail. Have also done the fuel relay test by turning on the ignition and checking continuity between 3 and 5 on the relay and it shows continuity all the time, swaped it out with the AC compressor relay and same result. Where can I go from here?