SHIM
SELECTION
USE THIS CHART WITH
METHOD 2.
I
,
DISTANCE ADD
MEASURED THESE
STEP
4
SHIMS
0.1
0.01
0
0.2
0.014
0.3
0.01
8
0.4
0.022
0.5
0.026
0.6
0.030
INJECTION
we in Inches)
DISTANCE
I
ADD
MEA:FtD
I
HHnlIiE
0.038
0.042
1.0
0.046
0.050
FIGURE
41.
SHIMMING THE PILOT
With shims and seal in place insert the pump into
cylinder block mounting pad, and insert mounting
screws. Torque the mounting screws (tighten alter-
nately) to
18-21
ft.-lb.
(24-28
Nrn).
Install the fuel inlet line and governor linkage. Bleed
the pump, and then install the fuel outlet line (see
INSTALLA
TION
section).
PSU
OR
MODEL
50
INJECTION
PUMP
The
PSU
or model 50 injection pump (Figure
42)
is
used on Onan
2-
and 4-cylinder water-cooled diesels.
Pumps that are almost identical, with only two injec-
tor line outlet ports, are used on the
two
cylinder
models.Thefunction of the pump asadistributorand
its location on the service side of the engine are the
same on both
2-
and 4-cylinder engines.
Repair
Internal repairs on the injection pumps require spe-
cial tools and step-by-step procedures for disassem-
bly and reassembly.
Replace wifba newpump anypump
G
that troubleshooting procedures
prove to
be
malfuncffoning.
Do
not attempt unaufho-
rized repair procedures
on
injection
pumps.
FIGURE
42.
INJECTION PUMP
Pump Operation
The pump face gear mates with and is rotated by a
drive gear on the engine camshaft, Figure
43.
The
face gear, pilot ring, and the reciprocating plunger in
the pump are rotated continually to assure positive
fuel distribution.
A
multi-lobed cam on the camshaft
rides on atappet assembly in the pump and drives the
plunger up and down.
OPERATING
LEVER
b
fm
A-
I
ll
T
MULTI-LOBE
CAM
FIGURE
43.
INJECTION PUMP TO CAMSHAFT
RELATIONSHIP
44
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