GMC 4000 Series Service Manual page 390

NOTE: The driven gear must be removed from
hub on pump shaft before the injection pump a s­
sembly can be removed from engine, by removing
three special bolts and washers.
12. Loosen and remove two driven gear-to-
hub bolts and special washers. (These are near top
position if engine is on No. 1 cylinder firing posi­
tion.) Use clean shop towel to prevent bolts and
washers falling in in gear train.
13. Remove shop towel and turn crankshaft
counterclockwise until third or bottom bolt and
washer is at the top and can be removed. Then
move crankshaft clockwise until pointer is again
at the T ,INJ." mark. Engine is now back in time.
14. Remove lower stud nut and washers at­
taching pump to engine front cover.
15. Remove upper stud nuts and washers at­
taching pump to front cover. Remove fuel injection
pump assembly (fig. 38).
NOTE: If engine is properly timed, it is not
always necessary to observe position of mark on
face gear (fig. 10) before removing pump. Position
of mark can be observed after pump removal; how­
ever, pump must be installed with face gear timing
mark in same position as when removed. Observe
position of timing mark immediately after pump
removal. If marks are positioned as in figure 10,
injection is beginning on #1 cylinder. If mark (4,
fig. ) is not visible as in figure
1 0
beginning on No. 4 cylinder.
INSTALLATION
If a new fuel injection pump assembly is being
installed, it will be necessary to transfer the fuel
line and oil line fittings from the removed pump
assem bly to the new pump. Observe the position of
each fitting as it is removed, and install it in same
position on new pump assembly.
CAUTION: Carefully clean any ac­
cumulated dirt from fittings before install­
ing in replacement pump assembly and
install dust caps to exclude any foreign
material when the fittings are installed.
Inspect gear teeth on injection pump drive
gear and driven gear before installing pump. Be
sure the mounting surface on pump flange and the
mating surface at engine front cover are clean.
Remove the cover from right-hand side of in­
jection pump so alignment marks on face gear and
ledge can be seen.
1. Set fuel injection pump driven gear inplace
through access opening in top of engine front cover.
Driven gear teeth must engage teeth on pump drive
gear and flat side of gear must be toward rear as
shown in figure .
1 2
2. Check position of rocker arms at No. 1 cyl­
inder to be sure No. 1 piston is on compression
G M C S E R V I C E M A N U A L
FUEL INJECTION SYSTEM— TORO-FLOW ENGINE
stroke. Observe "INJ." mark on crankshaft damper
assembly (fig.
pointer on front cover as shown.
injection pump assembly, look for mark on edge of
face gear. If mark is not visible, turn the pump
shaft until mark comes into view, then set the
mark on hub in alignment with pointer in pump
housing. Mark and pointer are shown in figure 10
(Items
on pilot at forward side of pump mounting flange,
then lift the injection pump assembly into position
on mounting studs (4).
on each of the three pump mounting studs and
tighten the nuts evenly to seat pump flange firmly
on cover.
hub in relation to elongated slot in driven gear (fig.
12). If necessary, change the position of gear so
threaded hole in hub is approximately centered in
slot in gear. The gear teeth can be lifted out of
mesh with drive gear to change gear position. Re­
ferring to the "Suggestion" under Step 2 of "Re­
moval" procedure, take precautions to prevent
accidental dropping of bolts and washers into en­
gine cavity.
, injection is
1 0
( , fig. 13) with special washer through driven gear
6
slot and into mounting hub, and tighten with fingers.
third bolt and washer can be installed with fingers.
Then move crankshaft clockwise until pointer lines
with "INJ." mark. Using a 7/8-inch wrench (fig.
13) hold pump hub timing mark in alignment with
pointer and tighten gear mounting bolts 35 to 40
foot-pounds torque.
earlier in this section.
installed on engine front cover assembly, it is sug­
gested that engine crankshaft be turned counter­
clockwise a few degrees, and then turned back until
the "INJ." mark on damper (fig. 10) is aligned with
pointer. This will assure tooth contact on drive
side of all gears. Make final check to be sure No.
cylinder is on compression stroke, then refer­
1
ring to figure
(9) with pointer (
through opening in pump housing. Mark (4) on face
gear will be in the position shown, to left of mark
(5), if the pump is properly timed to the engine.
new gasket. Also use new gasket and install gear
access cover on top of engine front cover assembly.
Install rocker arm cover.
ting on injection pump housing. Connect fuel return
) which must be indexed with the
1 1
3. Through opening in right-hand side of fuel
and 9).
8
4. Referring to figure 38, install seal ring (5)
5. Install plain washer, lock washer, and nut
. Check the position of threaded hole in pump
6
7. Start two of the driven gear mounting bolts
. Move crankshaft counterclockwise until the
8
NOTE: Refer to "Setting Injection Timing"
SUGGESTION: Before the gear access cover is
, check for indexing of timing mark
1 0
), and also view face gear (3)
8
9. Install side cover on pump housing using
10. Connect lubrication oil supply line to fit­
Sec. 6M
Page 379