GMC 4000 Series Service Manual page 386

CAUTION: As supply pump is remov­
ed the governor inner spring guide (1,fig.
35) and spring spacers are free to fall out
of place. Exercise necessary care to pre­
vent loss of these parts. Plug the fuel line
openings to prevent dirt from entering.
OIL SEAL REPLACEMENT
If the fuel supply pump is in satisfactory oper­
ating condition and does not require disassembling
for other repairs, the oil seal (9, fig. 35) may be
replaced without disassembling the pump. Pry out
old seal assembly and press new seal into bore
with the seal lip pointed toward the pump gear. Use
sealer sparingly at outer circumference of seal to
prevent leakage.
If the pump has been disassembled, a suitable
punch may be inserted through bore in insert to
drive the seal assembly out of the insert.
FUEL SUPPLY PUMP DISASSEMBLY
Key numbers in text refer to figure 35, unless
otherwise indicated.
1. Remove governor outer spring guide (11)
from pump assembly.
2. Remove the five screw s and lock washers
( ) which attach cover to insert (4). Tap the insert
6
lightly with plastic hammer to separate insert
from cover. Remove gears from insert.
3. Remove relief valve retainer screw (7) and
remove spring and relief valve assembly
fig. 31).
SUPPLY PUMP COMPONENT INSPECTION
Key numbers in text refer to figure 7.
1. Inspect for wear in gear cavities in pump
insert (1). Also look for evidence of worn surface
or scoring on cover ( ) area at which contact is
1 0
made with gears.
2. Note condition of the oil seal in pump in­
sert. New oil seals are available for service use.
3. Examine relief valve parts. Use new parts
when assembling pump if any of the components
are defective. Relief valve (9) should pass fuel
through center in only one direction.
4. Inspect idler gear shaft pin (2) which is a
p ress fit in bore in insert. If pin is worn, scored,
or loose in bore, obtain a new insert and pin a s­
sembly.
INSTALLATION
Key numbers in text refer to figure 35.
1. Check governor, inner and outer springs to
make certain the inner spring guide (
spacers are in place. Outer spring guide (11) must
be in place at pump insert (4).
2. Place gasket ( ) on cover flange with bolt
8
holes aligned.
G M C S E R V I C E M A N U A L
FUEL INJECTION SYSTEM— TORO-FLOW ENGINE
1
2
3 Governor Outer (Low
4 Pump Insert
5 Pump Cover
and 9.
( 8
) and original
1
Governor Inner (High 6 Insert to Cover Screws
and Lock Washers
Speed) Spring Guide
7 Relief Valve Retainer
Flat on Pump Drive
Screw
Shaft
8 Gasket
Speed)Spring 9 Oil Seal
10 Pump Idler Gear Pin
11 Outer (Low Speed)
Spring Guide
Figure 3 5 — Fuel S u p p ly P u m p R e m o v e d from
Injection P u m p A s s e m b ly
Figure 3 6 — Fuel Injection P u m p H yd ra u lic
H e a d A s s e m b ly Replacem ent
Sec. 6M
Page 375
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