How many spark plugs does a Mercedes Benz E320 have?

In this blog, we will find out the number of spark plugs used in the different generations of the Mercedes Benz E 320 model. The following question is also answered in this blog: how to replace the spark plugs in the Mercedes E 320? How to inspect the spark plug? When to replace the spark plugs in the Mercedes Benz E 320? 

How many spark plugs does a Mercedes Benz E320 have?

The number of spark plugs used in the Mercedes Benz E 320 is given in the table below:

The first generation in the Mercedes Benz E 320 has 6 spark plugs. The W124 is powered by the  M104 engine, all the spark plugs had separate ignition coils located under the cylinder head cover. The second and third generations of the E 320s had the M112 engine.

The M112 engine is a V 6-cylinder engine but there are 2 spark plugs for each cylinder. It is one of the reasons behind the great reliability and smooth running of the M112 engine even after thousands of miles.

The spark plugs are connected to the Ignition coil packs. Two coils are integrated into a single unit and there are 6 ignition coil packs in the second and third generations of the Mercedes Benz E320. The output stages are also integrated into the coil pack in order to keep the temperature low in the engine control unit.

The twin spark ignition coil pack consists of a primary winding and a secondary winding. The secondary winding has two outputs instead of a single. The power supply of the primary coil comes from the circuit 87 relays and the actuation line is connected to the engine control unit.

When the engine control unit interrupts the primary coil current flow at the time of the ignition timing. A sudden collapse of the magnetic field in the primary winding induces the ignition voltage in the secondary winding. The ignition voltage reaches the spark plug through a diode and a resistor.

As there are twin spark plugs in the W210 and W211 the ignition voltage is distributed by the ignition coil pack between the two spark plugs. One spark plug ignites at the time of the power stroke of the cylinder while another spark plug ignites during the exhaust stroke of the cylinder. Both of the ignition timings are offset by 360degrees.

The secondary coil circuit consists of a diode in order to prevent waste spark when the primary coil is engaged again. Hence, it is not possible to measure the resistance of the secondary winding. The secondary voltage in the Mercedes Benz is also 30,000 to 45,000 volts.

Without a proper tool, it is not possible to measure the secondary voltage of the ignition coil. Only the power supply of the primary coil can be checked with the help of a digital multimeter.

How to replace the spark plug in the Mercedes Benz E 320?

The procedure to replace the spark plugs in the Mercedes Benz E 320 is given below:

• Turn off the ignition and store the key at least 2 M away from the car.
• Locate the ground terminal of the main battery and disconnect it.
• Remove the engine compartment panels, remove the ignition coil panel in case of the W124.
• Disconnect the electrical couplers connected to the ignition coils
• Remove the ignition coils and keep them in a clean and dry place.
• Used the spark plug socket to remove the spark plugs.
• Install the new spark plugs and apply torque according to the specifications
• Apply spark plug grease in the ignition coil and install it in the reverse order.
• Connect the battery and start the engine.

If the high voltage line of the ignition coil is difficult to remove, spray a penetrating oil or silicone lube on in the spark plug barrel. Connect the electrical couplers of the ignition coil according to the sequence. A high-temperature grease can be used on the threads of the new spark plug.

How to inspect the spark plugs?

The procedure to inspect the spark plus is given below:

• Check the spark plug electrode gap, a feeler gauge can be used to measure the electrode gap.
• Inspect the tip of the spark plug, and look for soot particles or oil deposits on the spark plug.
• Use a digital multimeter to measure the resistance of the spark plug. Ideally, the resistance between both the terminals of the spark plug is between 5000 to 15000 ohms.
• Observe the top insulator and the insulator nose. Replace the spark plug if the insulator is damaged as it can create a short circuit between the electrode and the thread.

The gap between the ground electrode and the center electrode is the most important measurement in the spark plug. If the gap is more than 2.0 mm then the ignition voltage and combustion timing are affected. 

When to replace the spark plugs in the Mercedes Benz E 320?

The spark plugs in the Mercedes Benz E 320 must be replaced after every 4 years or after 60,000 kilometers. This is a part of preventive maintenance, and the spark plug replacement is carried out at the 4-year major service.

Other than the 4-year service, spark plugs are also replaced if the insulator on the center electrode is damaged. The insulator is made from ceramic material and it can break from the thread area. The broken piece of the insulator falls on the spark plug electrode and causes combustion misfiring.

If the spark plugs are not replaced then there can be carbon build-up on the electrode that reduces the fuel economy and performance of the engine. The cost of replacement of spark plug in the W 210 and W 211 E 320 is more as there are 2 spark plugs in each cylinder.

If there is oil in the spark plug barrel, it means that there is a leak in the cylinder head cover. If oil is present only on the electrode of the spark plug, it indicates that the valve stem seal is leaking. Hence, the cause of the oil leak must be rectified before replacing the spark plugs.

Conclusion

This blog answered the question-how many spark plugs are present in the Mercedes E 320 and also explained the procedure to replace the spark plugs. Spark plugs are used to ignite the air-fuel mixture in the gasoline engine. Hence, the spark plugs must be replaced every 4 years or after 60,000 km.