Hi Les, I had the same concern with mine. I did the leak down test that we have in the service manual to determine whether it was the check valve in the regulator; or the check valve in the fuel pump. Mine was apparently the fuel pump check valve, although I still haven't changed out the pump. Service manual says that quick loss of pressure indicates the check valve in the press. reg., and a slow loss indicates check valve in the fuel pump(this is of course after determining that it's not leaking through an injector).
It doesn't seem to be a problem for us, as it starts up OK, but perhaps it would start instantly instead of a second or two if I changed out the fuel pump. Didn't you just get a new 55 pump? Mine leaks down to near zero pressure, but holds just enough(maybe 1/2psi) to keep fuel in the lines. How long should a healthy check valve hold fuel pressure? A week, a month; I don't know.[/QUOTE]
From the Manual
7. Pressure should not fall below 2.5 bar (36 psi) after 30 minutes.
8. If pressure falls below 2.5 bar (36 psi) within 30 minutes, it must be determined if a fuel injector, the check valve within the fuel pump, or a fuel tube/line is leaking.