Replacing spark plugs, checking high-voltage wiring (Opel Corsa C)

Caution: The electronic ignition system generates very high voltage! Be careful and take all necessary precautions when servicing any components of the system, including not only the main (ignition module, high voltage wires), but also related items such as spark plug connectors, tachometer and other equipment!

Caution: All spark plug replacement work should only be performed on a cold engine (engine temperature can be touched by hand) - otherwise, when removing the spark plugs on a hot engine, the internal thread of the spark plug installation hole on the cylinder head may be damaged.

Removal, installation, condition check and maintenance of spark plugs

1. The correct functioning of the spark plugs largely determines the efficiency of the engine. It is important that the engine is equipped with spark plugs of the type specified by the manufacturer (see Specifications). Attempts to "improve" the engine by installing more expensive and seemingly better spark plugs will most likely lead to the opposite result. On a serviceable engine, the need for unscheduled maintenance of spark plugs arises extremely rarely; do not unscrew the spark plugs for inspection without necessity. To avoid accidental damage to the electrodes, do not service or clean the spark plugs without using special equipment.



2. To replace the spark plugs, you need a special spark plug head (16 mm) complete with an extension, cardan joint and torque wrench (see accompanying illustration). Using a torque wrench will help ensure that the correct amount of tightening force is applied to the spark plugs.

Caution: Use a spark plug wrench with an elastic insert to prevent damage to the spark plug insulator!

3. To gain access to the spark plugs, you must first remove the ignition module (see Chapter 5), and on the Z16SE engine, simply disconnect the high-voltage (HV) wires from the spark plugs - pull on the tip, not the wire itself. If the markings on the HV wires have worn off, mark their installation position with a marker or electrical tape before disconnecting the wires.

4. On DOHC engines, the spark plugs are deeply recessed into the spark plug wells, so you will need a key extension to remove them (see accompanying illustration). After placing the head on the spark plug, connect the drive and, carefully turning the crank counterclockwise, unscrew the spark plug.



5. Compare the removed spark plug with the condition chart below, which will allow you to qualitatively assess the overall condition of the engine.

6. Checking the condition of the spark plugs gives a good idea of the engine condition. If there are no traces of any deposits on the insulator of the central electrode, this indicates that the air-fuel mixture is too lean, or that an excessively "hot" spark plug is used (heat dissipation from the insulator to the housing on "hot" spark plugs is much less intense than on "cold" ones).



7. The presence of black carbon deposits on the electrodes indicates that the mixture is too rich, and if the carbon deposits also have an oily consistency, you should also consider a more detailed assessment of the degree of wear of the internal components of the engine.

8. A golden or grey-brown coating on the insulator confirms the engine is in good condition and the air-fuel mixture is correctly configured.

9. Modern engines use spark plugs of various types. The interelectrode gaps are set at the manufacturer and, as a rule, do not require any adjustments. If necessary, the interelectrode gaps should be set in accordance with the spark plug manufacturers' instructions.

10. The measurement of the interelectrode gap is performed using a special wire-type probe (see accompanying illustration 22.10a). When adjusting, only the side electrodes should be bent - attempts to deform the central electrode are fraught with irreversible damage to the insulator. If a blade-type feeler gauge is used to measure the spark plug gap, the gap can be considered adjusted correctly when the blade of the feeler gauge passes into it with slight resistance (see accompanying illustration 22.10b).

22.10a. Checking the interelectrode gap size using a wire-type gauge

22.10b. Checking the interelectrode gap using a blade-type feeler gauge

11. Before installing the spark plug, make sure that the threads on the body and the outer surface of the spark plug are well cleaned.

12. If damage to the threaded connection is found during inspection of the spark plug, the spark plug must be replaced, and if the thread in the cylinder head is damaged, it is necessary, without removing the head, to cut a new thread using a special tool for a special transition sleeve that is screwed onto a standard spark plug. For this purpose, there are appropriate tools and various repair kits on sale (for example, the company BERU).

13. Thread one of the new spark plugs into the appropriate hole in the engine by hand. After making sure that the spark plug is not twisted in the threads, tighten it to the required torque (see Specifications). To make the spark plug installation procedure easier, pull a piece of flexible fuel hose over its tail (see accompanying illustration) in order to eliminate the possibility of thread stripping, since the slightest biting will simply cause the hose to start turning. Proceed in a similar manner to install all the remaining spark plugs.





14. Reinstall all components that were removed. On the Z16SE engine, perform the inspection and maintenance procedure (see below) before connecting the spark plug wires to the spark plugs. The connection of the wire should be performed by rotating and reciprocating movements of its tip - the latter should fit tightly onto the spark plug tail. Proceeding in a similar manner, connect the wiring to the remaining spark plugs - do not mix up the FIRE ORDER (see Specifications).

Checking the condition and servicing spark plug wires (z16SE engines)

15. The condition of the high-voltage electrical wiring should be checked regardless of whether the spark plugs have been replaced or not.

16. The check begins with an external inspection of the wire insulation with the engine running. Drive the car into a dark room, start the engine, open the hood and make sure there is no sparking on the wires. Sparking is a sign of insulation breakdown.

17. For a more thorough check, disconnect and remove the high voltage wires, following the instructions given in paragraph 3 (see above). It is recommended to check the wires one by one to avoid violating the order of their connection during installation.

18. Wipe the entire length of the wire with a clean cloth, completely removing traces of dirt and grease from the surface of the insulation. Carefully check the insulation of the removed wire for cracks, burn marks, and other damage, signs of developing corrosion of the internal contact. Carefully inspect the inner walls of the tip - corrosion usually appears as a brittle crust-like white coating.



19. Try not to bend the wire at sharp angles to avoid damaging the integrity of the conductor cores inside the insulation. It is recommended to replace the high-voltage wiring as a set, even if only one of the wires fails.

20. When installing the wires, pay special attention to the tightness of their tips. If necessary, remove the corresponding tip again and bend the terminals inside the rubber cover.

21. Even if the ignition system is in excellent condition, failures may occur when starting in damp weather. If necessary, spray the system components with a moisture-absorbing spray. Ask in car accessory stores.

Coal deposits

Symptoms: The presence of soot indicates an over-rich fuel-air mixture or weak spark intensity. Causes misfires, difficult starting and leads to unstable engine operation.

Recommendations: Check if the air cleaner is clogged, if the fuel level in the float chamber is too high, if the air damper is stuck and if the contacts are too worn. Try using spark plugs with a longer insulator, which increases resistance to contamination.

Oiling

Symptoms: Oiling of the spark plug is caused by worn out oil deflector caps. Oil gets into the combustion chamber through worn valve guides or piston rings. Causes misfires, difficult starting and leads to unstable engine operation.



Recommendations: Perform mechanical repairs and replace spark plugs.

Overheat

Symptoms: Porous, white insulator, erosion of electrodes and absence of any deposits. Leads to a reduction in spark plug life.

Recommendations: Check that the installed spark plugs are of the correct heat range, that the ignition timing is set correctly, that the fuel/air mixture is not too lean, that there are no vacuum leaks in the intake manifold and that the valves are not stuck. Also check the coolant level and that the radiator is not clogged.

Too early ignition

Symptoms: The electrodes are melted. The insulator is white, but may also be contaminated due to misfiring or foreign particles entering the combustion chambers. May cause engine failure.

Recommendations: Check the glow number of the installed spark plugs, the ignition timing, and the quality of the mixture (isn't it too poor?), whether the cooling system is clogged and whether the lubrication system is functioning normally.

Conductive gloss

Symptoms: The insulator has a yellowish color and a polished appearance. Indicates a sudden increase in temperature in the combustion chambers during sharp acceleration. Normal deposits melt, acquiring the appearance of a varnish coating. Leads to misfires at high speeds.

Recommendations: Change the spark plugs (cooler, while maintaining the same driving style).

Short circuit of electrodes

Symptoms: Combustion waste gets into the interelectrode space. Solid deposits accumulate, forming a bridge between the electrodes. Leads to ignition failure in the cylinder.

Recommendations: Remove deposits from the interelectrode space.

Normal condition of the candle

Symptoms: Grey-brown color and slight wear of the electrodes. The glow number of the spark plugs corresponds to the type of engine and its general condition.

Recommendations: When replacing spark plugs, install spark plugs of the same type.

Ash formation

Symptoms: Soft, brownish deposits on one or both spark plug electrodes. These are caused by oil and/or fuel additives. Excessive buildup can insulate the electrodes and cause misfires and rough running under acceleration.

Recommendations: If deposits accumulate quickly, replace the oil seals, which will prevent oil from entering the combustion chambers. Try changing the fuel brand.

(Article posted on a web portal OpelBook)

Wear

Symptoms: Rounding of the electrodes with a small accumulation of deposits at the working end. Color is normal. Causes difficulty starting the engine in cold, wet weather and increased fuel consumption.

Recommendations: Replace the spark plugs with new ones of the same type.

Detonation

Symptoms: Insulators may be chipped or cracked. Insulator damage may also result from improper spark plug gap adjustment. Piston damage may result.

Splashing

Symptoms: After a long period of misfire, deposits may become loose while the combustion chamber remains at operating temperature. At high speeds, deposits flake off the piston and stick to the hot insulator, causing misfires.

Recommendations: Replace the spark plugs or clean and reinstall the old ones.

Mechanical damage

Symptoms: Can be caused by foreign material entering the combustion chamber or by the piston hitting a spark plug that is too long. Leads to cylinder failure and piston damage.

Recommendations: Remove foreign particles from the engine and/or replace the spark plugs.