The working end or pump section is known as a "Roller Cell" pump. Very
common in fuel applications. It is a positive displacement pump meaning
that once filled with fluid, in order for the pump to turn, the fluid has
to move. Since gasoline is poor lubricant, rollers are used to seal the
parts instead of vanes as would be more typical in hydraulic applications.

The displacement principle is similar to gear type pumps. As the rotor
section turns in that oval or off set housing, the displacement of the
chamber on the suction side is larger than the output side. The fluid
fills the chamber and as the rollers move, the fluid is pushed or squeezed
into the smaller displacement on the pressure side.

The motor including the brushes and armature are immersed and cooled by
the fuel. The lack of oxygen is the only keeping the works from igniting.
This is why running the tank low or having a restricted suction side is
not a good thing. You also should never remove a pump and try testing it
on the bench. You can become handless.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Don Spence
Sent: Wednesday, July 25, 2007 6:02 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Fuel pump mechanism question

Anthony has posted a photo of a disassembled pump. Can someone
explain how this pumps fuel? Are the innards immersed in the fuel as
it transits the pump? what provides the pumping action?

> Date:    Tue, 24 Jul 2007 10:05:33 -0500
> From:    Anthony Kimmons <akimmons@GMAIL.COM>
> Subject: Re: Vapor lock? Static electricity? Help!
>
> I just cut open my fuel pump that was new, but had been sitting in my
> van (installed) for a couple of years. Wondered what had made it stop
> working.
>
> Posted a picture here if anyone is interested-
> http://www.anthonykimmons.com/vanagon
>
> I could  see nothing wrong with it. Looked pretty new. Seemed clean,
> but would not turn.
> Still not sure what caused it to fail.