Date: Tue, 23 Jul 2013 14:41:11 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Fuel pump noise? Fuel filters.
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At 01:17 PM 7/23/2013, neil n wrote:
>Of the two spare pumps I have, each has a screen at the inlet. At the
>very least, this may provide some means of protection? Certainly would
>clog fast with a dirty tank and no pre pump filter.
The tank has a screen, inaccessible.
The pump has a screen, accessible to be washed out through the inlet fitting.
I just turned the ends off my dud pump on the lathe. I was hoping to
be able to show how the roller pump is constructed as it's quite an
elegant bit of kit, but this one is a solid block of rust. Too bad,
I was fantastically lucky in my choice of where to make the cut.
As a general description though, from the inlet end there's a fine
metal screen across the whole diameter of the pump housing leaving a
little chamber to accumulate crud. This can be flushed out with
Brakleen spray from the inlet end. Then the pump itself fills the
space for part of an inch, and includes the motor bearing on one
end. It operates something like a vane pump except with little
rollers to provide the seals instead of vanes. It's sealed to the
housing by an O-ring, so it takes in on one side and discharges on
the other, directly into the space occupied by the motor armature and
magnets (which is most of the overall size). At the far end is a
plastic cap also sealed with an O-ring. This contains the motor
brushes, the other motor bearing which is simply four little
extensions of the plastic, and a check valve built into the base of
the outlet nipple. This cap is pressed into the aluminum cup which
forms the rest of the housing and the lip of the cup is crimped around it.
The motor is lubricated and cooled strictly by the gasoline flowing
through it. The commutator and brushes operate immersed in gasoline.
The actual operating parts of the pump, the rotor and rotors, are
only maybe a fat eighth of an inch thick IIRC. The plate that forms
the pump chamber is made of a very fancy grade of hardened
not-sure-what with a gray finish. It is magnetic, and I can't
remember what if anything I concluded from a spark test many years
ago. I've still got the bit kicking around someplace. I doubt I'll
disassemble this one farther, it doesn't look like an enjoyable project.
Yours,
David
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