Removed and disassembled the injection/metering pump today to determine
cause of oil leak. There is a seal on the output adjustment shaft that
was
compressed and hard (looked baked) and obviously not sealing (used pump
from
Atkins).
One interesting note - the output adjustment (arm normally connected to
the
throttle linkage) is not a proportional control; it is basically a two
position setting, low flow at low end (idle), and high flow for anything
just above idle position. So in our application where we just tie it
off,
the arm position is not critical, anything about 10-15 degrees or so off
the
low stop is as high a flow setting as it is going to get.
Not able to determine the internal porting, but it does not appear to be
positive displacement to each of the 4 ports.
Al
(snip)
the oil entrance is right behind the relieve hole on the other side of
the
shaft bore, coming out of the cover wall.
Oil will leak out when the shaft is bad. Under normal condition, there
can
be no pressure buildup in the pump, because it is all open to the crank
case
via the oil inlet and relieve hole. BTW, the shaft has a flat section on
its
running surface toward the pump for oil feed.
The actual pump does not have a drive plate. The picture shown on the
ACRE
site has no resemblance with the physical design of the real pump. There
are
even functional differences. The most significant functional difference
is
that the piston makes two strokes per revolution.
Richard Sohn
N-2071U
unicorn@gdsys.net
-Al Gietzen wrote:
Just a further note on the metering pump; that seal for the adjustment
shaft
is apparently hard to come by, so I found that two 1/16 x ¼ i.d. x 3/8
o.d.
O-rings side by side in the groove solved the problem just fine.
Also, as noted below, the position of the adjustment arm is not critical
as
long as it is somewhere off the bottom end. A nice way to anchor it is
to
remove the arm, turn it over, place it back on the shaft and mark where
it
hits the stop pin. Then cut off the arm, notch it to fit the pin, and
reinstall it (still turned over from the original position, of course).
See
attached photo. It results in positioning the adjustment about half way
between the stops.
Al
While we are on the subject Richard had one disassembled at Rotary
Roundup.
Here is one of Al's pictures and one of mine showing the pump
disassembled.
BTW I don't recommend this 2 rotor 13B pump for use on a three rotor. Not
enough apex seal
cooling and lube oil for all three rotors.
Paul Lamar
Brett & Tiana wrote:
I've just recently replaced all three seals in my (12A) metering pump. I
found that the shaft seal that had been put there months earlier by a friend
was leaking again.
It was a new neoprene seal of the same 1/4" OD and 1/16th" cross-section as
mentioned previously, but only held up for two weeks before leaking again.
This may have been exacerbated by the fact that I'm running 2-cycle oil from
a reservior rather than the heavier 4-cycle oil from the pan.
On the advice of another RX7 guru I switched to a metric size Viton seal
(marginally larger OD, not certain of actual OD in mm), which was a slightly
tighter fit. I also replaced the old and brittle end cap seals using Viton
13/16" OD X 1/16" cross-section o-rings. (Yes, they will conform to the
diamond-shaped seal grooves on the pump body.)
Almost 2 months later there is no sign of a leak. Hope this helps.
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/
Copyright 1998-2004 All world wide rights reserved.