Testing fuel accumulator/checkvalve

[S-Class Guru]

Still looking for the cure to heat-soak lean-start condition on my 103.
The guys here keep mentioning fuel pressure loss in the accumulator/check valve.

I unhooked the fuel line inlet at the throttle body and stuck on a pressure gauge. Then I pressured the fuel pump up to 78 psi and walked away.
After 1 hour the pressure had dropped by 15 psi, to 63.
overnight, it dropped to 30 psi.

Is this acceptable for accumulator/check valve performance?

DG