1989 Ram B150 not holding fuel pressure
 

I have a 1989 Throttle body injected 5.2L B150
I have to crank this van for about 10 seconds before it will fire up. I put a fuel pressure gauge inline and this is what I found:
System does not hold pressure. With key in "on position" no pressure is formed. While cranking, no pressure is formed, but the injectors drip and van eventually fires up. While running, it shows 15psi (which according to manual, is good). As soon as I shut it off, all pressure is lost.
So, what component is responsible for holding and maintaining pressure in this TBI system? I already replaced the fuel filter for good measure. I am assuming it is either my fuel pump or the fuel pressure regulator. Would love it if someone could shed an explanation on what is going on. Thanks

There is a check valve built into the fuel pump. I suspect that is leaking and is the source of your problem.

Damn! I didn't want to have to drop the tank to replace the pump. Is this for sure the problem?

Can anyone else verify that this is likely the problem before I go dropping the tank?

bumped