NOTE: A leaking fuel injector or high-pressure fuel line may cause
a rough idle, Black smoke, poor engine performance, poor fuel
economy and fuel knock. Since a leaking high-pressure fuel
line may cause the same symptoms, check for leaking high
-pressure fuel line before checking fuel injector.
1) To determine which injector or line is malfuntioning,
start engine and check each cylinder output using scan tool. If scan
tool is not available, start engine and engine allow to idle. Loosen
high-pressure fuel line nut at each fuel injector in turn and listen
for a decrease in engine speed. Tighten high-pressure fuel line nut to
30 ft. lbs. (40 N.m). Go to next step.
2) To check for a leaking high-pressure fuel line, start
engine and allow engine to idle. Inspect high-pressure fuel lines and
connections for signs of fuel leakage by placing cardboard over high-
pressure fuel line and connection. Note if leak is being detected by
fuel being sprayed onto the cardboard. If leak exists, repair leak by
tightening high-pressure fuel line nut to 30 ft. lbs. (40 N.m) or
replacing high-pressure fuel line as necessary. If high-pressure fuel
line is replaced, bleed air from fuel system. See FUEL LINE BLEEDING
under FUEL SYSTEM in REMOVAL, OVERHAUL & INSTALLATION - TRUCKS -
DIESEL article. If no leaks are found, go to next step.
3) Remove suspect injector. See FUEL INJECTOR under FUEL
SYSTEM in REMOVAL, OVERHAUL & INSTALLATION - TRUCKS - DIESEL article.
Test injector with a diesel fuel injector tester. Follow tester
instructions. Replace fuel injector if fuel injector opening (pop)
pressure is not 4250-4750 psi (299-334 kg/cm
). Replace injector if
any leaks are noted at 291 psi (20 kg/cm ) less than opening (pop)
pressure. Inspect injector for burrs, cracks, wear and plugging. Check
spray pattern. If any problems are noted, replace injector.
FUEL INJECTION PUMP TIMING
Improper fuel injection pump timing may result in low power,
excessive smoke and poor fuel economy. To check fuel injection pump
timing, see FUEL INJECTION PUMP TIMING in ADJUSTMENTS - TRUCKS -
DIESEL article.
INTAKE MANIFOLD AIR HEATER
NOTE: Intake manifold air heater is used to heat incoming air
before entering each cylinder. Warming of incoming air aids
in engine starting and improved driveability during cold
ambient temperatures. Engine Control Module (ECM) uses input
signals from various sensors for controlling intake manifold
air heater relays.
SUMMARY
If no faults were found while performing basic diagnostic
procedures, proceed to SELF-DIAGNOSTICS - JEEP, TRUCKS & RWD VANS
article. If no diagnostic trouble codes are found in self-diagnostics,
proceed to TROUBLE SHOOTING - NO CODES - DIESEL article for diagnosis
by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent
diagnostic procedures.
CYLINDER BLOCK
* PLEASE READ THIS FIRST *
NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
BLOCK CLEANING
Only cast cylinder blocks should be hot tank cleaned.
Aluminum cylinder blocks should be cleaned using cold tank method.
Cylinder block is cleaned in order to remove carbon deposits, gasket
residue and water jacket scale. Remove oil galley plugs, freeze plugs
and cam bearings prior to block cleaning.
BLOCK INSPECTION
Visually inspect the block. Check suspected areas for cracks
using the Dye Penetrant inspection method. Block may be checked for
cracks using the Magnaflux method.
Cracks are most commonly found at the bottom of the
cylinders, the main bearing saddles, near expansion plugs and between
the cylinders and water jackets. Inspect lifter bores for damage.
Inspect all head bolt holes for damaged threads. Threads should be
cleaned using tap to ensure proper head bolt torque. Consult machine
shop concerning possible welding and machining (if required).
CYLINDER BORE INSPECTION
Inspect the bore for scuffing or roughness. Cylinder bore
is dimensionally checked for out-of-round and taper using dial bore
gauge. For determining out-of-round, measure cylinder parallel and
perpendicular to the block centerline. Difference in the 2 readings
is the bore out-of-round. Cylinder bore must be checked at top, middle
and bottom of piston travel area.
Bore taper is obtained by measuring bore at the top and
bottom. If wear has exceeded allowable limits, block must be honed
or bored to next available oversize piston dimension.
CYLINDER HONING
Cylinder must be properly honed to allow new piston rings to
properly seat. Cross-hatching at correct angle and depth is critical
to lubrication of cylinder walls and pistons.
A flexible drive hone and power drill are commonly used.
Drive hone must be lubricated during operation. Mix equal parts of
kerosene and SAE 20w engine oil for lubrication.
Apply lubrication to cylinder wall. Operate cylinder hone
from top to bottom of cylinder using even strokes to produce 45 degree
cross-hatch pattern on the cylinder wall. DO NOT allow cylinder hone
to extend below cylinder during operation.
Recheck bore dimension after final honing. Wash cylinder
wall with hot soapy water to remove abrasive particles. Blow dry with
compressed air. Coat cleaned cylinder walls with lubricating oil.
DECK WARPAGE
Check deck for damage or warped head sealing surface. Place
a straightedge across gasket surface of the deck. Using feeler gauge,
measure clearance at center of straightedge. Measure across width and
