Yes indeed, it is a lift pump, usually for diesel. It is still on the spec for a NYC garbage truck, and it's plumbed with tees and checks to be used as a helper via switch on the dash. The end cap comes off to reveal a screen.

2014 Durango R/T
2004 Dodge Ram 3500 SRW SLT short quad Cummins 6 speed
1998 Dodge Durango SLT 5.2
1971 Plymouth Duster-
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