Hi all,

Yes a main pump can still pump gasoline to the rail and flow as long as the pump stays running.

It can do this with a fail check valve on the main pump outlet but will not hold pressure immediately after shutting off. It can also be a slight restriction to the pump to keep the pump primed, per say, even though it’s almost a positive displacement pump but has only guided rollers.
One more reason for a feed pump besides tank level.
Trash around the rollers does not help the capacity either.
The check valve was about $11 back in my day but probably about $18 now but has to comes with a new pump for the above reasoning.

He can take it off the present pump and check it by trying to blow through it in both directions. In one direction it will not or should not any air pass.

The spring In these can wear on one side and the spring collapses and it goes bye-bye.
It can have trash inside there. The tank filter sock is the only thing that protects the main pump.
The main pump can also wear excessively and that trash, from inside the pump, hits the check valve.
Both are rare but I have lost one check valve so I know about the collapsed spring. It’s not a theoretical guess, for me this time, but a fact. (:)

The check valve can cause all kinds of issues, if you don’t know the pressure in the rail or if it’s being held in the rail after shut down.
So Art is correct, the in-tank fuel pump probably has been out for a long time and now the end result is no fuel!

A long “on going” bad thing can lead to a “no going” worse thing!
(:-). 85 posts and counting.

Phil