GMC 4000 Series Service Manual page 369

y' V
PROBABLE CAUSES /
1. Engine Stop Mechanism
X
Out of Adjustment or
Not Functioning
2. A ccelerator Linkage
A. Out of Adjustment X
B. Binding or Broken.
X
3. Inadequate Fuel Supply
A. Fuel F ilters Clogged X
X
B. Defective Fuel Supply
PumD
C. Overflow Valve or
X
Spring Defective
X
D. Fuel Tank Vent Plugged
X
E. Air Entering System
4. Fuel Injection N ozzles
A. N ozzles Defective,
X
Leaking, or Worn
B. Incorrect Nozzle
X
Opening Pressure
C. Incorrect Torque on
Nozzle Holder Bolts
D. Nozzle Valve Sticking X
E. Nozzle Seat Leaking, Dirty X
5. Adjusting Screws
A. Idle Screw Out of
Adjustment
B. High Speed Screw
Out of Adjustment X
6. Governor Springs
A. Outer Spring
B. Inner Sorine
7. D efective D elivery Valve X
8. Damaged or Defective
Hydraulic Head
X
9. Fuel Injection Pump
Out of Time with Engine X
FUEL SYSTEM TROUBLE D IAG N O SIS CHART
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X X
X X
X
X
X X
X X
X X
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X X
X X X
X X
X
X
X X
X X
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X X
X X
X X X
X
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/ v / i ° / RECOMMENDED REMEDY
Refer to "Diesel Engines" in this section for
X X
control linkage adjustments.
Make necessary adjustments or repairs to A c­
X X
celerator Linkage as instructed in "Diesel
Engines" in this section.
X X
Service or replace the fuel filter s as previ­
ously directed under "Diesel Engines" in this
section.
X X Overhaul or replace fuel supply pump.
Remove and disassem ble overflow valve. Re­
X X
place parts as necessary.
X
Clean vent or replace cup.
X X Make necessary repairs to elim inate air leaks.
Overhaul and/or adjust injection n ozzles. Pro­
X cedure for servicing nozzles is given later in
X
this section.
X X Remove nozzle, test and adjust as n ecessary.
Use torque wrench and check nozzle bolt torque.
X
Overhaul nozzle assem bly.
Clean nozzle seat and install new gasket.
Adjust as instructed under "Engine Tune-up."
Adjust as instructed under "Engine Tune-up."
X
Check and adjust governor springs referring
to procedure given in this section.
X
X X Replace delivery valve assem bly as directed
X
under "Fuel Delivery Valve Replacem ent" in
"Service Ooerations."
Replace fuel injection pump with properly c a l­
X X ibrated pump assem bly. Refer to pump replace­
ment instructions given in this section.
Refer to applicable instructions for timing the
injection pump given in this section under
X X X X
"Injection Timing."
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