GMC 4000 Series Service Manual page 361

Sec. 6M
Page 350
ENGINE FUEL SYSTEM— DIESEL
1 F uel Injection Pump
A ssem bly
2 Pump D isch arge Line
3 B lee d e r Plug
4 Secondary F ilte r
5 F ilte r Clamp Bolt
6 F ilte r Mounting
Bracket
Figure S — Secondary Fuel Filter and Connecting Lines
of filter assembly.
2. Loosen nut connecting line (2) to elbow on
filter, then loosen filter clamp bolt (5). Raise fil­
ter (4) in the bracket to provide access to drain
If filter becomes excessively restricted, it will result in loss of
engine power and could result in expensive fuel injection pump repair.
Therefore, it is important to service fuel filters at specified intervals.
G M C S E R V I C E M A N U A L
7 F ilte r D rain Plug
8 C lips
9 Fuel Suction Line
(To Pump)
10 F uel Pump A ssem b ly
11 F uel Supply Line (To
Injection Pump)
T-5558
plug (7) and nut connecting line (11) to elbow at
bottom of filter.
3. Remove bleeder plug (3), then remove drain
plug (7) and drain filter into receptacle.
CAUTION: Use care to prevent dirt
from entering fuel lines when replacing
filter.
4. Clean fittings at bottom of filter of dirt,
then disconnect line (11) at elbow. Disconnect line
(2) from filter elbow, then remove filter assembly
from bracket (6). Remove inlet and outlet elbows
from filter assembly.
5. Install inlet and outlet elbows in new filter.
Position new filter assembly at bracket (6) with
word "TOP" upward. Connect line (11) to elbow at
bottom of filter, and connect line (2) to elbow at top
of filter.
6. Tighten fuel line nuts, check drain plug (7)
for tightness, then position filter in clamp and
tighten filter clamp bolt (5). Remove vent (bleeder)
plug from top of fuel filter and fill filter with
CLEAN fuel. Install plug loosely, start engine, and
run at idle. Watch for fuel to flow at plug (3). When
bubbles cease to appear and fuel flows steadily,
tighten plug (3) securely.