I'm currently diagnosing a hot start problem with my 1972 350sl.

I attached a fuel pressure guage to the line going to the cold start valve and turned on the ignition. The pressure went to 28psi and dropped to 14psi after about an hour. Is this acceptable? I have the MB manual for this engine but their pressure readings are stated in bars. What is the psi eqivillent?
Also I must say that I highly appreciate and respect the knowledge that the professionals and lay enthusiast convey through this forum. I do not take it for granted.
I consider my tinkering a hobby and it's usually a rewarding challenge to work on my cars and keep them running properly.
My inquiring on this forum is not intened to bypass local professional help. I do take my cars to a competent mechanic when I have to.
I also enjoy sharing my MB experiences with others through the various forums.
I just felt I had to mention this after reading a post that sounded like the person did not want to pay ( "get ripped off" as they put it) to have their 1998 E320 diagnosed at a MB dealership.
In my opinion working on the older vehicles with carbs and early fi systems is one thing, but the newer cars with all thier computers and electronics, how else does one expect to get a proper diagnosis of their problem?

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72 350SL #69
73 450SL Parts Car?
78 450sl Parts Car
79 450SLC - Sold
1985 280sl
87 190E 2.6 - Donated
90 300E-Junked
97 E420