
14-92
FUEL
SYSTEM
• A broken injection pump timing mechanism spring
will cause the timing to be fully advanced resulting
in torque loss, a fuel knock and possible engine over
heating.
An improperly operating KSB (cold start) solenoid
will cause white smoke during engine warm-up. The
KSB solenoid is not serviceable.
A defective or non-adjustable fuel injection pump
can cause starting problems or prevent the engine
from revving up. It can also cause:
• Engine surge at idle • Rough idle (warm engine)
• Engine miss under load
• Low power
• Excessive fuel consumption
• Poor performance
• Low power
• Black smoke from the exhaust • Blue or white fog like exhaust
• Incorrect idle or maximum speed A worn fuel injection pump plunger can effect fuel
pressure and the amount of fuel injected. This results in reduced engine power. In most cases, if the injec
tion pump is delivering fuel from one outlet, it will deliver fuel from all outlets. If the internal plunger is defective, the fuel injection pump must be re
placed.
Engine power is also effected by the governor set
ting and performance. Do not attempt to adjust the governor. If the governor seals on the external adjustment screw are broken, the fuel rate may
be out of adjustment. The warranty of the injec tion pump and the engine may be void if the
seals have been tampered with or removed.
FUEL
INJECTORS
A leaking fuel injector can cause fuel knock, poor
performance, black smoke, poor fuel economy and
rough engine idle. If the fuel injector needle valve
does not operate properly, the engine may misfire and produce low power. A leak in the injection pump-to-injector high pres
sure fuel line can cause many of the same symptoms as a malfunctioning injector. Inspect for a leak in the
high pressure lines before checking for a malfunc
tioning fuel injector.
WARNING:
THE
INJECTION PUMP SUPPLIES HIGH
PRESSURE
FUEL
OF
APPROXIMATELY
59,000
KPA
(8,000
PSI) TO
EACH INDIVIDUAL INJECTOR
THROUGH THE HIGH
PRESSURE
LINES. FUEL UN
DER
THIS AMOUNT
OF
PRESSURE
CAN
PENE
TRATE THE SKIN AND CAUSE PERSONAL INJURY,
WEAR
SAFETY GOGGLES
AND
ADEQUATE PRO
TECTIVE CLOTHING. AVOID CONTACT
WITH
FUEL
SPRAY
WHEN BLEEDING HIGH
PRESSURE
FUEL
LINES.
WARNING:
DO NOT
BLEED
AIR
FROM
THE
FUEL
SYSTEM
OF A
HOT ENGINE.
DO
NOT ALLOW FUEL
TO SPRAY ONTO THE EXHAUST MANIFOLD WHEN
BLEEDING
AIR
FROM THE FUEL SYSTEM.
To determine which fuel injector is malfunctioning,
run the engine and loosen the high pressure fuel line nut at the injector. Listen for a change in engine
speed (Fig. 14). Tighten the line nut. If engine speed
drops,
the injector was operating normally. If engine
speed remains the same, the injector is malfunction
ing. Test all injectors in the same manner one at a
time.
Fig. 14
Inspecting
Injector Operation
Once an injector has been found to be malfunction
ing, remove it from the engine and replace it. Refer
to Diesel Engine Service Procedures for injector re moval and installation.
FUEL
SUPPLY
RESTRICTIONS
CAUTION:
Do not
operate
the
engine
if the
fuel
sup ply
line
has
a
restriction
of
more
than
12.7
kPa
(3.75
in
Hg).
Refer
to
Lift
Pump
Test.
Fuel supply line restrictions can cause starting
problems and prevent the engine from revving up.
The starting problems include; engine miss under load, low power and blue or white fog like exhaust.
Test all fuel supply lines for restrictions or blockage.
Flush or replace as necessary. Bleed the fuel system
of air once a fuel supply line has been replaced.
FUEL/WATER
SEPARATOR
FILTER
A blocked or clogged fuel/water separator filter can
cause starting problems and prevent the engine from
revving up. It can also cause engine miss under load,
low power and blue or white fog like exhaust. The maximum allowable fuel pressure drop across
the fuel/water filter separator is 21 kPa (3 psi).

•
FUEL SYSTEM
14-93 There is a drain at the bottom of the separator fil
ter (Fig. 13). Place a drain pan under the drain tube. With the engine not running, hold the drain open
until all water and contaminants have been removed and clean fuel exits the drain. Dispose of mixture in
drain pan according to applicable regulations.
If excess water gathers in separator/filter in a short
time,
the fuel tank must be removed, drained and cleaned.
HIGH
PRESSURE FUEL LINE RESTRICTIONS
High pressure fuel line leaks can cause starting
problems, poor engine performance and engine miss under load. Restricted high pressure lines can cause starting problems, poor engine performance, engine
miss under load and black smoke from exhaust.
WARNING:
USE
EXTREME
CAUTION
WHEN
IN
SPECTING
FOR HIGH
PRESSURE
FUEL
LEAKS.
IN
SPECT
FOR HIGH
PRESSURE
FUEL
LEAKS
WITH
A
SHEET
OF
CARDBOARD.
HIGH
FUEL
INJECTION
PRESSURE
CAN
CAUSE
PERSONAL
INJURY
IF
CONTACT
IS
MADE
WITH
THE
SKIN.
Start the engine. Move the cardboard over the high
pressure fuel lines and check for fuel spray onto the cardboard. If a high pressure line connection is leak
ing, bleed the system and tighten the connection. Re
fer to the 5.9L Diesel Service Procedures section for air bleeding procedures. Replace damaged, restricted
or leaking high pressure fuel lines with the correct replacement line.
CAUTION:
The
high pressure
fuel
lines must
be
clamped securely
in
place
in the
holders.
The
lines cannot contact each other
or
other components.
Do
not
attempt
to
weld high pressure
fuel
lines
or to
repair lines
that
are
damaged. Only
use the
recom
mended lines when replacement
of
high pressure
fuel
line
is
necessary.
KSB
SOLENOID
The KSB solenoid will click when it is energized
and de-energized. If the solenoid does not click when 12 volts is sup
plied to it, replace the solenoid.
MECHANICAL
LIFT
PUMP
An improperly operating lift pump can cause low
engine power. Inspect the fuel supply line to the
pump for restrictions, kinks or leaks. Fuel leaking
from the weep hole (Fig. 15) in the pump casing in
dicates a leaking pump diaphragm. The lift pump is not repairable and must be replaced as an assembly.
CAUTION:
Do not
operate
the
fuel
system
with
a
suction restriction
of
more than
95 MM Hg (3.75
inch Hg). Refer
to
Lift
Pump Test.
Fig.
15
Lift
Pump
Low lift pump output can be caused by a worn ec
centric on the engine camshaft. A properly operating lift pump will pump a minimum volume of 0.75 liter (0.70 U.S. quart) of fuel in 30 seconds at engine
cranking speed.
The maximum allowable pressure drop across the
fuel filter is 21 Kpa (3 psi). As the filter removes contaminants in the fuel, the pressure drop across
the fuel separator filter will increase. Frequent re
placement of the separator filter can indicate a worn lift pump. Refer to the Maintenance Schedule at the
front of this manual for recommended replacement intervals.
LIFT
PUMP
TEST
(1) Disconnect fuel inlet tube at the lift pump. (2) Install T-fitting between disconnected fitting
and lift pump inlet. Connect vacuum gauge to T-fit
ting.
WARNING:
USE
EXTREME
CAUTION
WHEN
EN
GINE
IS
OPERATING.
DO NOT
STAND
IN
DIRECT
LINE
WITH FAN.
DO NOT PUT
HANDS
NEAR
PUL
LEYS,
BELTS
OR FAN. DO NOT
WEAR
LOOSE
CLOTHING.
The vacuum gauge will not indicate a vacuum un
til the lift pump begins to operate at full capacity.
(3) Operate engine at approximately 1500 rpm for
30 seconds. Vacuum should not exceed 12.7 kPa (3.75
in. Hg).
(4) If vacuum exceeds 12.7 kPa (3.75 in. Hg) check
fuel tube for restriction. A partially clogged in-tank fuel filter can also cause excess vacuum.

14-100
FUEL
SYSTEM
•
DIESEL
FUEL
INJECTION
SYSTEM DIAGNOSIS
SYMPTOM CAUSE
ACTION
Starting problem Improper
fuel
Drain
fuel
tank,
flush
system,
fill
with
proper
fuel.
Change
filter
Empty
fuel
tank
or
fuel
tank
vent
blocked
Fill
tank, bleed system, check
tank
vent
Air in
fuel
system Bleed
fuel
system
Voltage not supplied to
fuel
solenoid or
fuel
solenoid
inoperative
Correct voltage supply problem or
replace solenoid
Clogged
fuel
filter
Replace
fuel
filter
Restricted or blocked
fuel
supply lines Remove restriction or replace lines
Leaking
injection
lines, damaged lines or
loose
connections Replace damaged lines or tighten
connections as necessary. Bleed
fuel
system
Wax buildup in
fuel
filter
(cold
weather
only) Replace
fuel
filter,
use recommended
diesel
fuel
Incorrect
injection
pump to engine timing Adjust
injection
pump timing
Malfunctioning air heating system Repair air heating system
Injection
sequence does not correspond
with
firing
order Install
fuel
injection
lines in correct order
Malfunctioning
KSB
valve Replace
injection
pump
Low or uneven engine compression Repair as necessary
Restricted or blocked
fuel
injection
lines Remove restriction or replace lines
Fuel
injection
pump malfunction or not adjustable Replace
fuel
injection
pump
Engine
Surge at
idle
Empty
fuel
tank
or
fuel
tank
vent
blocked
Fill
tank, bleed system, check
tank
vent
Air in
fuel
system Bleed
fuel
system
Low
idle
speed Adjust
idle
speed
J9H4-22

•
FUEL
SYSTEM
14 - 101
DIESEL FUEL
INJECTION
SYSTEM DIAGNOSIS-CONTINUED
SYMPTOM
CAUSE
ACTION
Engine
surges
at
idle
Fuel
injection
pump malfunction or
not adjustable Replace
fuel
injection
pump
Rough
idle
when engine Is warm Improper
fuel
Air in
fuel
system Drain
fuel
tank, flush system,
fill
with
proper
fuel
Bleed
fuel
system
Low
idle
speed Adjust
idle
speed
Injection
pump
rear
support bracket loose Repair as necessary
Restricted or damaged
injector
nozzle
Repair or replace as necessary
Injection
sequence does not correspond
with
firing
order Install
injection
lines in correct order
Low or uneven engine compression Repair as necessary
Fuel
injection
pump malfunctioning
or not adjustable Replace
fuel
injection
pump
Engine
mines under lead Improper
fuel
Drain
fuel
tank, flush system,
fill
with
proper
fuel
Empty
fuel
tank
or
fuel
tank
vent
blocked
Fill
tank, bleed system, check
tank
vent
Air in
fuel
system Bleed
fuel
system
Clogged
fuel
filter
Replace
fuel
filter
Restricted or blocked
fuel
injection
lines Remove restrictions or replace lines
Restricted or blocked
fuel
supply lines Remove restrictions or replace lines
Leaking
injection
lines, damaged lines or
loose
connection Replace damaged lines or
tighten
connections as necessary. Bleed
fuel
system. 1
J9114-23

14
- 102
FUEL
SYSTEM
—
•
SYMPTOM
CAUSI
ACTION
lupin*
mimes under Im4 Incorrect
injection
pump
timing
Adjust
injection
pump
timing
Restricted
or
damaged
injector
nozzle
Replace
or
repair
as
necessary
Restricted
or
blocked
fuel
injection
lines Install
fittings
proper positions
Fuel
Injection
pump malfunction
or
not adjustable
Replace
fuel
injection
pump
lew power Improper
fuel
Drain
fuel
tank, flush
system,
fill
with
proper
fuel
Empty
fuel
tank or
fuel
tank vent blocked
Fill
tank, bleed
system,
check tank vent
Control lever not going
to full throttle
position Adjust
throttle
linkage
Clogged
fuel
filter
Replace
fuel
filter
Intercooler
internally
blocked
or
leaking
Check
pressure
drop
across
intercooler.
If
pressure
drop is more than
4
in.
Hg,
clean
or replace
as
necessary.
Restricted
or
blocked
fuel
supply lines
Remove
restrictions
or
replace lines
Injection
pump overflow
fitting
switched
with
inlet
fitting
Install
fittings
in
proper positions
Leaking
injection
lines, damaged lines
or
loose
connections
Replace
damaged
lines
or
tighten
connections
as
necessary.
Bleed
fuel
system
Incorrect
injection
pump
to
engine
timing
Adjust
injection
pump
timing
Restricted or
damaged
injector
nozzle
Repair
or replace as
necessary
Clogged
or
restricted
air filter
Remove
restrictions
or
replace
filter if
necessary
Air
fuel
control
tube broken
or
leaking
Repair
or replace
as
necessary
Low
manifold pressure
Check
and repair turbocharger operation.
Check
intercooler and
air
pipes
for
blockage
Injection
sequence
does
not correspond
with
firing
order Install
fuel
injection
lines in correct
order
Low
or
uneven
engine
compression
Repair
as
necessary
Restricted or blocked
fuel
injection
lines
Remove
restrictions
or
replace lines
Incorrect
injection
pump
to
engine
timing
Check
injection
pump
to
engine
timing
Fuel
injection
pump malfunction
or
not adjustable
Replace
fuel
injection
pump J9114-253
DIESEL
FUEL
INJECTION
SYSTEM
DIAGNOSIS-CONTINUED

FUEL
SYSTEM
14-103
DIESEL FUEL
INJECTION
SYSTEM DIAGNOSIS-CONTINUED
SYMPTOM
CAUSE
ACTION
Excessive
fuel
consumption improper diesel
fuel
Use
correct
fuel
for conditions. Refer
to
owner's manual
Incorrect injection pump timing
Adjust
injection pump timing
Restricted or damaged
injector
nozzle Repair or replace as necessary
Clogged
or
restricted air
filter
Remove
restrictions or replace air
filter
if
necessary
Injection sequence does not correspond
with
firing order install
fuel
injection lines in correct order
Intercooler internally blocked
or
leaking
Check
pressure drop
across
intercooler.
If
pressure drop
is
more than
4
in. Hg,
clean or replace as necessary
Low
idle misadjusted
Adjust
idle stop screw
Malfunctioning
KSB
valve
Replace
injection pump
Incorrect injection pump to engine timing
Adjust
injection pump to engine timing
Fuel injection pump malfunction or
not adjustable
Replace
fuel
injection pump
Unabie to shut engine off Voltage to
fuel
solenoid
interrupted
or
fuel
solenoid
inoperative Correct voltage supply problem or
replace
solenoid
Either poor
performance,
black moke
or
low power Improper
fuel
Drain
fuel
tank, flush
system,
fill
with
proper
fuel
for conditions. Refer to owner's
manual
Air
in
fuel
system
Bleed
fuel
system
Intercooler internally blocked
or
leaking
Check
pressure drop
across
intercooler.
If
pressure drop is more than
4
in. Hg,
clean
or
replace
as
necessary
Restricted or blocked
fuel
injection lines
Remove
restrictions or replace lines
Incorrect injection pump timing
Adjust
injection pump timing
Restricted or damaged
injector
nozzle
Repair
or replace as necessary
Clogged
or restricted air
filter
Remove
restrictions or replace
filter
if
necessary
Air
fuel
control tube leaking or broken Repair or replace as necessary
Low
manifold pressure
Check
and repair turbocharger operation
Injection sequence does not correspond
with
firing order Install
fuel
injection lines in correct order
—
Low
or uneven engine compression
Repair as necessary
J9114-255

14-104
FUEL
SYSTEM
• DIESEL FUEL INJECTION SYSTEM DIAGNOSIS-CONTINUED
SYMPTOM
CAUSE
ACTION
Either poor performance,
black
smoke
or low
power
Injection
pump
to engine timing
Fuel injection pump malfunction or
not adjustable
Check
injection
pump
to
engine
timing
Replace
fuel
injection pump
White or blue fog-like exhaust in full-load range Improper
fuel
Drain
fuel
tank,
flush
system,
fill
with proper
fuel,
change
filter
Empty
fuel
tank or
fuel
tank vent blocked
Fill
tank, bleed
system,
check tank vent
Air
in
fuel
system
Bleed
fuel
system
Clogged
fuel
filter
Replace
fuel
filter
Restricted
or blocked
fuel
injection lines
Remove
restriction or replace lines
Restricted
or blocked
fuel
supply lines
Remove
restriction or replace lines
Wax
buildup in
fuel
filter
(cold weather
only)
Replace
fuel
filter,
use
recommended
i
diesel fuel.
Inspect
fuel
heater electrical connector for
damage.
Incorrect injection pump to engine timing
Adjust
injection pump timing
Injection pump overflow fitting switched
with inlet fitting Install fittings in
proper
positions
Fuel injection pump malfunction or
not adjustable
Replace
fuel
injection pump
Incorrect lale speed
Low
idle misadjusted
Adjust
idle
stop
screw
Fuel injection pump malfunction or
not adjustable
Replace
fuel
injection pump
Engine
does
not rev up Improper
fuel
Drain
fuel
tank,
flush
system,
fill
with proper
fuel,
change
filter
Empty
fuel
tank or
fuel
tank
vent blocked
Fill
tank, bleed
system,
check
tank vent J9114-26

•
FUEL
SYSTEM
14-105 DIESEL FUEL INJECTION SYSTEM DIAGNOSIS-CONTINUED
SYMPTOM
CAUSE
ACTION
Engine
does not rev up Control lever not
going
to
full
throttle
position
Adjust
throttle
linkage
Air
in
fuel
system
Bleed
fuel
system
Intercooler internally blocked or leaking
Check
pressure drop
across
intercooler.
If pressure drop is more than 4 in. Hg,
clean or replace as necessary
Clogged
fuel
filter
Replace
fuel
filter
Restricted or blocked
fuel
supply lines
Remove
restrictions or replace lines
Wax
buildup in
fuel
filter
(cold weather only)
Inspect
fuel
heater
electrical
connector
for
damage.
Replace
fuel
filter,
use recommended diesel fuel.
Incorrect injection pump timing
Adjust
injection pump timing
Injection pump overflow
fitting
switched
with
inlet
fitting
Install fittings in proper sequence
Low
or uneven engine
compression
Repair
as
necessary
Fuel injection pump malfunction or
not adjustable
Replace
injection pump
Infection pump runs hot Overflow blocked
Clean
overflow orifice or replace
fitting
J9114-254