Isuzu N-Series. Manual - part 475

Engine Mechanical (4HK1-TC)   6A-5

Crankshaft 
Tuftriding is given, while on the No. 1 balance weight
imprinted is the grade of each journal diameter.

EGR System
Based upon data, including water temperature, engine
speeds or engine loads, it is controlled via Engine
Control Module (ECM) to purify exhaust by recycling
part of it. 
Its main components include an EGR valve, an EGR
cooler and various sensors.

Connecting Rod Cap Bolt
The angular tightening method of the connecting rod
cap bolt further increases reliability and durability.

Common Rail-type Electronic Control Injection
System
The common rail-type electronic control injection
system is composed of a fuel supply pump that sets the
target pressure of high-pressure fuel and supply it, a
fuel rail that measures such high-pressure fuel and an
fuel injector that turns it into a fine spray and injects it.
Each is controlled via ECM based upon various
signals, while injection timing or fuel injection quantity
is controlled under every possible driving condition.

Fuel Injector 
The fuel injector is a 7-hole nozzle that adjusts fuel
injection quantity or injection timing by opening or
closing an electromagnetic valve on the head of the
fuel injector.
ECM corrects the dispersion of fuel injection quantity
between fuel injectors according to ID code data in
memory. At the replacement of fuel injectors, ID code
data should be stored in ECM.

Fuel Filter with Sedimenter
It is a fuel filter with sedimenter that gets rid of water by
making use of the difference in specific gravity between
light oil and water, which comes with an indicator that
notifies you that it is filled with water.

Preheating System
The preheating system consists the ECM, the glow
relay, glow plugs and the glow indicator lamp. The
preheating system is operated when the engine coolant
temperature is low, and make the engine easy to start.

Lubrication System
It is an oil filter with full-flow bypass, which uses a
water-cool oil cooler and oil jet to cool the piston.

Functional Inspection
Inspection/adjustment of valve clearance

1. Inspection of valve clearance

a. Remove the cylinder head cover.
b. Remove the fuel injector harness assembly.
c. Loosen the terminal nuts alternately to remove.
d. Remove the leak-off pipe.

e. Rotate the crankshaft to make the No.1 cylinder

meet the compression top dead center (TDC).

Notice:
There are 2 timing marks on the crankshaft pulley. 
Mark (1) is near the cylinder block and is used to bring
the 4HK1-TC engine to TDC.
Mark (2) is not applicable to this engine.
Be sure to use mark (1) when bringing the engine to
TDC.

• Insert a 0.4 mm (0.016 in) thickness gauge into

a clearance between the rocker arm and the
bridge to check it and adjust it if needed.

Caution:
Adjust while being cold.

Valve clearance

mm (in)

Intake valve

0.4 (0.016)

Exhaust valve

0.4 (0.016)

N6A6002E

N6A6003E

6A-6   Engine Mechanical (4HK1-TC)

2. Adjustment of valve clearance

Caution:
Adjust valve clearance carefully so that the bridge
contacts the end of the 2 valve stem.

a. Completely loosen all of the bridge and rocker

arm adjusting nuts and adjusting screws (8 nuts
and 8 screws).

b. Place a 0.4 mm (0.016 in) thickness gauge

between the No. 1 cylinder rocker arm end and
the bridge cap.

c. Tighten the rocker arm adjusting screw until the

thickness gauge is snug (not tight) between the
rocker arm end and the bridge cap.

d. Tighten the rocker arm lock nut.
e. Tighten the bridge adjusting screw until the

bridge contacts the valve head.

f. Tighten the bridge lock nut.
g. Check that the thickness gauge is still held

snugly between the rocker arm end and the
bridge cap. If it is too tight, slightly loosen the
bridge adjusting screw and lock nut to restore
snugness. 

h. Remove the thickness gauge.
i. Repeat Steps b through h for the remaining

cylinders.

Tighten:
Bridge lock nut to 22 N

⋅m (2.2 kg⋅m/16 lb⋅ft)

Legend

1. Rocker Arm
2. Bridge Cap
3. Bridge

 

a. With a thickness gauge kept inserted,

tighten an adjusting screw of the bridge
lightly and make sure that the tip of the
adjusting screw touches the end of valve

stem and the movement of the thickness
gauge has become tight.

b. Then, check if the end of the valve stem on

the opposite side is unstable or hits
diagonally. If so, loosen the bridge adjusting
screw a little so that the end of the valves on
both sides may touch properly.
Valve bridge clearance: 

± 0.1 mm (0.0039

in) or less

c. After making an adjustment so that the end

of the valves on both sides may touch
properly, tighten up an adjusting screw nut
of the bridge with a minus driver so that the
bridge adjusting screw may not rotate.

Tighten:
Adjusting screw nut to 22 N

⋅m (2.2 kg⋅m/16 lb⋅ft)

Caution:
If the adjusting screw of the bridge is poorly adjusted,
the bridge would tilt and be pushed down and seized,
which may damage the bridge guide, for example.
Thus, adjust it accurately.

Tighten:
Rocker arm adjustment screw nut to 22 N

⋅m (2.2 kg⋅m/

16 lb

⋅ft)

Bridge adjustment screw nut to 22 N

⋅m (2.2 kg⋅m/16

lb

⋅ft)

Adjustment table

N6A6004E

Cylinder  No.

1

2

3

4

Valve 
arrangement

IN EX IN EX IN EX IN EX

No. 1 cylinder
Compression 
TDC

{

{

{

{

No. 4 cylinder
Compression 
TDC

×

×

×

×

N6A6005E

Engine Mechanical (4HK1-TC)   6A-7

• If the No. 1 cylinder is the compression

TDC, adjust a valve clearance with { mark
given on the table and if the No. 4 cylinder is
the compression top dead center, that with 

×

mark. 

• Attach the harness assembly to the fuel

injector.
Tighten the harness bracket with the
designated torque.

Tighten:
Harness bracket to 48 N

⋅m (4.9 kg⋅m/35 lb⋅ft)

• Attach the terminal nuts to the fuel injector.

Tighten:
Terminal nuts to 2 N

⋅m (0.2 kg⋅m/17 lb⋅in)

Notice:

• Tighten the terminal nuts alternately in order to

prevent imbalance in tightening because they are
unified.

• Do not tighten the nuts too tightly because it leads to

damage to the terminal studs.

• Install the cylinder head cover.

Refer to “Cylinder Head Cover.”

Compression pressure inspection

• Warm up the engine.
• Remove a minus terminal of the battery and

remove all the glow plugs.

• Remove the harness connector for the fuel injector

built on the lower head cover (no fuel will be
injected).

Caution:
When the harness connector is removed, ECM judges
that it broke down and DTC is recorded. Upon
completion of measurement, never fail to clear memory
of ECM.
(For how to clear memory of ECM, refer to Section 6E)

Legend

1. Fuel Injector Harness Connector

 

• Install the minus terminal of the battery.
• Turn on the starter to emit foreign matter within the

cylinders.

N6A6006E

N6A6007E

N6A6008E

6A-8   Engine Mechanical (4HK1-TC)

• Install an adapter and a gauge of a compression

gauge of the special tool.

Compression gauge set: 5-8840-2008-0
(Compression gauge: J-26999-12, 
Gauge adapter: EN-46722)

• Turn on the starter to inspect compression

pressure.

• Measure each cylinder one by one.

Caution:
To keep engine speed at 220 rpm or more, use fully
charged batteries.

• Remove a compression gauge of the special tool.
• Remove a minus terminal of the batteries.
• Install a harness connector for the fuel injector built

on the lower head cover.

• Install all the glow plugs.

Tighten:
Glow plugs to 20 N

⋅m (2.0 kg⋅m/15 lb⋅ft)

• Install a minus terminal of the batteries.

A list of defective phenomena

• Engine does not turn over.
• Engine turns over but does not start.
• Excessive black exhaust smoke.
• Excessive white exhaust smoke.
• Engine knocking.
• Abnormal engine rotation.
• Abnormal battery charging.

Compression pressure

MPa (kg/cm

2

/ psi) /

220 rpm

Standard

2.60 – 2.89 (26.5 – 29.5 / 

377 – 419)

Limit

1.96 (20.0 / 284)

Differences among 
the cylinders

294 kPa (3.0 kg/cm

2

 / 43 

psi)

N6A6009E