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Sparkplugs

MEANING OF REFERENCES

INSTALLATION RECOMMENDATIONS

CASE OF REPLACEMENT

MEANING OF REFERENCES

Thread diameter

	Thread Diameter	Key
A	18 mm	25.4 mm
B	14 mm	20.8 mm
C	10 mm	16 mm
D	12 mm	18 mm
E	8 mm	13 mm
G	1/2 mm	23.8 mm
J	12 mm	18 mm
AB	18 mm	20.8 mm
BC	14 mm	16 mm
BK	14 mm	16 mm
DC	12 mm	16 mm

Dessin de la bougie

L	Short insulation
M	Compact type
P	Prominent insulation
R	Integrated resistor
U	Surface discharge
Z	Integrated inductance

Thermal index

2	Hot

4
5
6
7
8
	85
9
	95
10
	105
11
12
13	Cold

Length of thread

E	19 mm
H	12.7 mm
L	11.2 mm
EH	Filetage seeds
	Cap L=19 mm
	Thread L=12.7 mm
F	Conical seat
	A-F typeb 10.9 mm
	B-F typeb 11.2 mm
	B-EF type 17.2 mm

Drawing of the spark plug

C	Oblique mass electrode
F	Conical seat
G	Fine nickel alloy electrode
GV	Palladium gold center electrode - Special shape
J	2 ground electrodes
K	2 ground electrodes
M	2 ground electrodes for MAZDA rotary engine or 18.5 mm insulator
T	3 ground electrodes
Q	4 ground electrodes
P	Platinum tip
S	Copper central electrode
U	Semi-surface discharge type
V	Ot-Palladium center electrode
VX	Central electrode Platinum
W	Tungsten electrode
X	Internal spark gap

SECTION OF A STANDARD SPARK PLUG

NGK MOUNTING RECOMMENDATIONS

ELECTRODE SPACING

It is sometimes necessary to adjust the electrode spacing because it does not always match the specific setting for each application.

The adjustment of the electrodes is essential for an optimal combustion !

REPLACEMENT OF A SPARK PLUG

1. Use a suitable spark plug wrench.
2. Wait for the engine to cool before removing the spark plug.
3. Turn the ignition cable cap slightly and remove it by pulling on the cap, not on the cable.
4. Remove the caps one at time so that they do not get mixed up
5. Make sure the cap and ignition cable are not damaged.
6. Loosen the spark plug by 1/4 turn and clean the dirt with compressed.
7. Remove the spark plug.

8. Clean the spark plug seat and refit a new s spark plug by screwing it in by hand without using grease on the threads.
9. VScrew in the spark plug with the recommended tightening torque
(see table opposite).
10. RReplace the ignition cable, making sure the cap is properly that the cap is properly attached.
11. For the other cylinders, repeat steps 4 to 10.
12. Check the condition of the ignition system.

TIGHTENING TORQUE (NGK data)

USE A TORQUE WRENCH

Cast iron cylinder head

Aluminium cylinder head


Ø	18 mm	14 mm	12 mm	10 mm	8 mm	18 mm	14 mm
N.m	35 - 40	25 - 30	15 - 25	10 - 15	-	20 - 30	10 - 25
m.kg	3,5 - 4,0	2,5 - 3,0	1,5 - 2,5	1,0 - 1,5	-	2,0 - 3,0	1,0 - 2,5
N.m	35 - 40	25 - 30	15 - 25	10 - 15	8 - 10	20 - 30	10 - 25
m.kg	3,5 - 4,0	2,5 - 3,0	1,5 - 2,5	1,0 - 1,5	0,8 - 1,0	2,0 - 3,0	1,0 - 2,5

// Ø 18 et 14 mm
1/2 - 2/3 turn
(180° à 240°)

// Ø 12 et 10 mm
1/2 turn
(180°)

// Ø 8 mm
1/3 turn
(120°)

The angles are given as an indication. Please refer to the recommended angle indicated on the candle box

A large part of the heat is dissipated through the parting line.

Too much or too little tightening is detrimental to good heat dissipation and can lead to engine damage.

CASE OF REPLACEMENT

SYMPTOMS

POSSIBLE CAUSES

SOLUTIONS

Used electrodes Lack of engine power Misfiring Increased fuel consumption	Exceeding the periodicity of replacement	▸ Replace the spark plug
Dry or wet fouling Mad ignition	Air/fuel mixture too rich Incorrect thermal range (too cold) Delayed ignition Incorrect eletrode spacing Oil consumption	▸ Adjusting the air/fuel mixture ▸ Checking the thermal index ▸ Check the ignition delay ▸ Check the distance between the electrodes ▸ Check oil consumption
Overheating Fused, welded electrodes	Incorrect thermal range Ignition advance Insufficient cooling Air/fuel mixture too lean Poorly tightened spark plug	▸ Check the spark plug recommendation ▸ Check the ignition advance ▸ Check for a cooling problem cooling ▸ Check the quality of the mixture ▸ Tighten the spark plug to the recommended torque with a torque wrench
Deposits Bad ignitions or no ignition	Poor fuel quality Poor oil quality Poor engine condition	▸ Check the fuel used ▸ Check the quality of the oil used ▸ Engine control
Broken or cracked ceramic Bad ignition or no ignition	Mechanical shocks Thermal shocks Engine vibrations Poor sealing Badly tightened spark plug	▸ Check the condition of the cylinder head gasket ▸ Check for vibration problems engine ▸ Tighten the spark plug to the recommended torque with a torque wrench
Torn off thread	Use of an unsuitable tool Too much torque applied	▸ Use a torque wrench ▸ Respect the recommended torque