1993 DGC 3.3 hard starting

My GC 3.3L has become hard to start, van runs fine once started, filter
and pump were replaced 2 years ago, about 50,000kilomters ago, this just
up and started.
Checked and cleaned all the relay connectors, didn't help, fuel pressure
is like 20# when it won't start but when it decides to start it goes to
40#+.
I have to turn the key on listen for pump to stop then turn it off then
on listen for pump to stop then about the third time the pump won't
start so I turn it over and sometimes it starts but most times it won't,
10 -15 second cranking and it won't start but turn it over and count to
3 then shut it off and do it again and sometimes it starts if not it
will on the next try.
Fuel pressure does not hold on a shutdown, it bleeds out.

Is this a back flow valve problem in the fuel pump?
Fuel pressure regulator?
Dirty injectors not closing?
How do I check to see which one it is?

Thanks

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System spec is 48 pounds. If you cannot attain/maintain that, the pump
and/or pressure regulator is/are faulty.

Pump and/or pressure regulator

If it were that, the engine would run very poorly (very rich).

 

Thanks for the reply Daniel,

Now the question is how to I go about testing the regulator or the
backflow of the pump?

I really don't want to pull the tank, been there 3 or 4 times 2 years
ago when I installed a brand new carter pump.

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