Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a method and apparatus for
changing a fuel pump of an internal combustion engine of the
type having a fuel pump mounted on one side of the engine
and driven by a push rod which is reciprocated by an
internal camshaft of the engine.
In all V-8 engines produced by General Motors from the
year 1955 to the present, the fuel pump is mounted on the
right hand side of the engine at a location a short distance
from the front of the engine. The fuel pump is driven by
the usual single camshaft of the engine which extends long-
tudinally of the engine and is centrally disposed in the
engine. A push rod extends between the camshaft and an
actuator member of the fuel pump and reciprocates on rota-
lion of the camshaft. Because the camshaft is located in a
plane above the level of the fuel pump, the push rod is
disposed in a slanted position with the actuator engaging or
outer end being lower than the cam engaging. When the fuel
pump is removed for repair or replacement, the push rod
tends to slide toward the outside of the engine 90 that when
the fuel pump is being replaced, the push rod may have to
be reinserted into its operating position. Because of the
internal structure of the engine and the need to have the
outer end of the push rod held against the actuator of the
fuel pump while the fuel pump is moved into position for
bolting to the engine, many tedious and frustrating attempts
are usually required to properly relocate the push rod, and
thus the labor cots involved in repairing or replacing the
fuel pump are unacceptably high.
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In all of the above-ldentified ~1-8 engines of General
Motors, which include engines identified by the cubic inch
displacement volumes of 265, 283, 305, 307, 327 and 350,
there are provided at the front end of the engine a number
of threaded bores in the engine block, the bores being
closed by way of short bolts screwed into the block. The
bores, one of which intersects the passage through which the
push rod extends, normally do not serve any purpose but are
provided to allow for special engine mounting arrangements
or the mounting of accessories.
It is an object of the present invention to provide a
special screw means which can be used after the bolt
normally received in the bore intersecting the push rod
passage has been temporarily removed so as to gently hold
the push rod against displacement when the fuel pump is
removed for repair or replacement.
The screw means or holding device of the present
invention includes an elongated member of a length longer
than the threaded bore which extends into the engine block
from the front thereof and intersects the push rod con-
twining passage, the elongated member having an inner push
rod engaging end, an outer end for finger engagement when
turning the member into or out of the threaded bore, and an
intermediate threaded portion.
According to another aspect of the present invention
there is provided a method of changing the fuel pump of an
engine of the above described type, which method includes
the steps of removing the bolt from the threaded bore in the
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front of the block of the engine and hand threading into the
bore a push rod holding device having a push rod engaging
end and a threaded intermediate portion. The device is
tightened by hand only sufficient to press against the push
rod and thereby hold the push rod against movement in its
passage. The bolt means which secure the fuel pump to the
engine block are then removed, and subsequently the repaired
or replacement pump is placed in position with the inner
face thereof in engagement with the machined surface of the
block and the actuator thereof extending into the passage
and engaging the outer end of the push rod. The bolt means
are then rethreaded into the block to hold the fuel pump in
place. The holding device is then removed from the threaded
bore in the front of the engine and the bolt is replaced in
the threaded bore.
In the accompanying drawings which illustrate embody-
mints of the invention,
Figure 1 is a front view of an engine of the type in
which the present invention can be used in the changing of a
fuel pump;
Figure 2 is a side view of the engine of Figure 1 as
seen from the right hand side;
Figure 3, which appears on the same sheet as Figure 1,
is a partial sectional view through the engine of Figure 1,
cut away along the line 3--3 of Figure 2 to show the
relative position of the fuel pump, push rod and camshaft;
Figure 4 is a simplified, partial side view of the
engine with a portion cut away in the area of the fuel pump
to illustrate the position of the push rod;
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Figure 5 is a side vie of the holding device of the
present invention;
Figure 6 is a cross sectional view through a portion of
the engine as seen from the line 6--6 of Figure 1, but with
the holding device of Figure 5 in position;
Figure 7 is an enlarged cross section of a portion of
the threaded engagement between the holding device and the
engine block, and
Figure 8 is a side view of an embodiment of the holding
device which is an alternative to that shown in Figure 5.
In Figures 1 and 2, the reference number 10 denotes a
V-8 engine of a type used by General Motors in automobiles
and light trucks since 1955 and in which a mechanical fuel
pump if is mounted at a low position immediately adjacent
the front of the engine on the right hand side thereof. The
fuel pump is removably secured to the side of engine block
12 by means 13 which is in the form of a pair of bolts. The
engine block is cast iron, and an area 14 of the block
immediately under the fuel pump is machined. A gasket 19
is provided between an inner mounting surface of the fuel
pump and the machined area 14 of the block. A centrally
disposed camshaft 15, which extends the length of the
engine is driven by a crankshaft 16 of the engine. The
camshaft 15, in addition to operating intake and exhaust
valves (not shown) of the engine, drives the fuel pump 11 by
way of a push rod 17. The fuel pump when activated during
operation of the engine draws fuel by way of a line or
conduit 20 from a fuel tank of the vehicle and delivers the
fuel by way of another fuel line 21 to a carburetor (not
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shown) located in a central position on top of the engine.
In the manufacture of the engine, a plurality of bores are
provided at the front of the engine. The bores, which are
threaded and extend rearwardly from the front surface of the
engine, are provided to allow for special mounting arrange-
mints or for the attachment of special accessories, and
normally are closed by way of common USE bolts 23 which
are threaded into the threaded bores
As may be observed in Figure 3, the camshaft 15 is
disposed in a plane which is located above the fuel pump 11
so that the push rod 17 slants downwardly from a camshaft
engaging end 25 to an outer or fuel pump actuating end 26.
Immediately within the machined area 14 on which the fuel
pump 11 is mounted, the block it provided with an enlarged
opening 27 into which an actuating member or arm 28 of the
fuel pump extends. The actuating arm 28 is biased to an
outwardly extending position so that engagement of the act
tufting arm with the push rod normally pushes the push rod
in firm engagement with the camshaft, i.e., the push rod is
held in engagement at all times at opposite ends between the
actuating arm at its outer end and the camshaft at its inner
end. On rotation of the camshaft 15, an eccentric lobe 30
thereof pushes the push rod outwardly so as to push the
actuating arm towards the fuel pump. As the camshaft no-
tales further and the lobe turns to the opposite side of the
camshaft, the biased actuating arm is free to push the push
rod back. The push rod therefore experiences a reciprocal
tying action in a passage 31 within the block 12. The small
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pivoting action experienced by the actuating arm as it is
pushed toward the fuel pump by the push rod and it then
allowed to be biased back provides the pumping forces within
the fuel pump while the engine is running.
During the normal life of an engine of the type
described above, a malfunction, such as a rupture in the
pumping diaphragm or a break-down of the one-way valves
provided in the inlet and outlet of the fuel pump, usually
develops one or more times, and this necessitates the
removal of the fuel pump for the purpose of overhauling or
replacement by a new or rebuilt unit. To remove the
existing fuel pump, inlet or supply line 20 and the outlet
line 21 are disconnected. the securing means 13 in the form
of the bolts are then removed so that the fuel pump can be
pulled away from the engine. When the fuel pump is pulled
away from the engine and the actuator arm 28 disengages the
outer endow the push rod 17, which is about 5 3/4 inches
long, about 1/2 inch in diameter and weighs about five
ounces, and the push rod it free to slide downwardly in its
passage 31. As a result, when the replacement fuel pump is
brought into position the push rod must be moved back into
its normal position and this involves ensuring that the
inner end 25 of the push rod is moved into its proper
position relative to the camshaft, which is a difficult
procedure because the inner end of the push rod is
approximately 6 inches inside of the engine block and cannot
be seen while only a very short part of the outer end of the
push rod is accessible. Moreover, because the actuator arm
is spring biased ou~wasrd from the fuel pump, the actuator
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arm engages the push rod before the base of the fuel pump
engages the machined area I of the engine block. It then
becomes necessary to ensure that the push rod remains in its
proper place by its engagement with the spring biased
actuator arm as the fuel pump is pushed against the biasing
force of the actuator arm to its proper location against the
side of the engine. As this entire exercise becomes
virtually impossible to accomplish, various make-shift
tools, such as bent knives feeler gauges, strips of sheet
metal screwdrivers have been devised for use in an attempt
to insert something behind the fuel pump for holding the
push rod until the fuel pump substantially reaches its
mounted potion, An alternative approach which is tried as
well involves the use of a heavy grease around the push rod
to hold it in place as the fuel pump is moved into place,
but this is usually not successful because the engine heat
melts the grease and allows the push rod to become
displaced.
In the TV engines of the above described type, the
threaded bore 42 closed by the bolt 23, which is the upper
one at the front adjacent the fuel pump, intersects the
passage 31 as can best be seen in Figure 6. The distance D,
as shown in Figure 6, which is the distance from the front
face of the engine block to the front surface of the push
rod within the passage 31, is 1 inch. This is the distance
as measured axially through bore 42, which is provided with
internal threads 43.
Holding device 33 of the present invention, as isles
treated in Figure 3, consists of an elongated member which is
Lowe
formed of a material, such as aluminum, or other material
softer than the cast iron in the engine block. The outer
end of the elongated member is preferably of cylindrical
shape head 34 with a knurled outer surface of about 1/2 inch
diameter and 1/2 inch length. The cylindrical shape is
economical to produce in an item of the nature of holding
device, but of more importance, this shape is preferable to
a square or hexagonal shape so as to encourage tightening by
hand rather than with a wrench. The inner end of the
holding device includes a smaller cylindrical portion or
projection 36, which terminates in a flat smooth push rod
engaging end 35. As the threaded bore is 3/8 inch nominal,
the cylindrical portion 36 is of slightly smaller diameter
than the internal diameter of the internal threads 42 of the
bore. In the illustrated embodiment of Figure 5, the
diameter of the portion 36 is 1/4 inch OLD. The surface of
end 35 is separated from the cylindrical surface of portion
36 by way of a tapered surface to avoid any sharp edge.
An intermediate portion consisting of an unthreaded portion
39 immediately inside of the knurled head 34 and a threaded
portion 40 is nominally 3/8 inch with the threaded portion
being 3/8 US threads for reception in the internally
threaded 3/8 internally threaded bore 42. The threaded
portion 40 is separated from the inner cylindrical end
portion 36 by a tapered portion or shoulder 37. In the
illustrated embodiment of the holding device 33 shown in
Figure 57 the length of the inner cylindrical projection is
3/4 inch and the length of the tapered portion separating
the cylindrical end portion 36 and the threaded portion is
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1/16 inch. In the intermediate portion, the threaded port
Tony and -the unthreaded cylindrical portion are of a length
of about 3/8 inch and 5/16 inch, respectively.
As previously indicated, the distance from the front
face of the engine block to the push rod 17 in the passage
31 is 1 inch. Thus, when the holding device 33 is threaded
into the bore 42 a distance to bring the end 35 against the
push rod 17, only about 3/16 inch or about 2 1/2 to 3
threads of the threaded portion 40 are threaded into the
internal threads 43 of the bore 42. In 3/8 US threading,
the outside dimension of the threads, as shown at 41b in
Figure 7, is actually under-sized by about of 4/1000 of an
inch. In the illustrated embodiment of the invention of
Figures 5 to 7, at least the first 2 1/2 to 3 threads, as
shown at aye in Figure 7, are purposely made of a greater
under-size, say ~/1000 inch, this being illustrated in a
somewhat exaggerated form in Figure 7, so as to provide a
safety feature for preventing the holding device from being
tightened to tile extent that damage is caused to the push
rod 17, as will be described in more detail below.
According to the method of the invention, when it
becomes necessary to replace a fuel pump, the 3/8 inch bolt
is removed from the threaded bore, and the holding device 33
is threaded by hand into the bore 42 and it is tightened
only sufficiently tight to hold the push rod 17 against the
opposite side of passage 31 as shown in Figure 6. As the
holding device 33 is threaded into the bore 42, it contacts
the snide of the push rod at a point shown as 50 in figure 3.
If one attempts to unduly tighten the holding device 33, say
by turning it with pliers, the fact it it made of a
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relatively soft material and the threads which have entered
bore 42 are undersized the tips aye of the threads will
tend to strip away before sufficient pressure is applied to
damage the push rod or strip the internal -threads 43 of the
bore. Having inserted the holding device 33, the inlet and
outlet lines 20 and 21 are disconnected, and the bolts which
secure the fuel pump to the engine block are removed so that
the fuel pump can be taken from the engine. When installing
the new or reconditioned pump 11, the gasket 19 and gasket
go are applied to the pump, and after the actuator arm is
pushed against the outer end of the push rod, the bolts are
reinserted to connect the pump to the engine. The lines 20
and 21 are then reconnected, and at this stage the holding
device 23 can be removed and the normal 3/8 inch bolt
replaced in the bore 42.
In the alternative embodiment shown in Figure 8, the
holding device may be formed of harder metal. In this
embodiment the finger engaging portion is shown as being in
the form of a flat portion aye, which is more of the wing-
nut fashion. The threaded portion aye, which is inward from the cylindrical portion aye and separated from the inner
cylindrical portion aye by shoulder aye, is a normal 3/8 US
thread. The inner end 35 is formed, however, by a soft
insert 45, such as brass, to avoid damage of the push rod by
over-tightening of the holding device.
further alternatives and modifications to the above
described embodiments of the invention will be obvious to
those skilled in the art without departing from the spirit
of the invention as defined in the appending claims.
