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Servicing – be a bright spark

By autotech-nath on March 29, 2019

While ignition components have always needed a degree of maintenance, Rob Marshall looks at how modern systems, including engine management, can be affected by service neglect, incorrect replacement techniques and poor quality replacement parts.

It is surprising how many members of the public consider that classic cars are far easier to service than modern vehicles. At least modern ignition and engine management systems have negated the regular and fiddly need to set accurate contact breaker points gaps and ensure optimum dwell angles, both of which tended to be almost impossible to execute accurately in any case, when many distributor shafts possessed excessive play in their bearings…even when new. Close inspection for excessive pits on rotor arms and for evidence of ‘tracking’ on the inside of distributor caps has also been consigned to the dustbins of history in most cases, although the principles are not entirely irrelevant today, as we shall see. 



Even so, modern cars require a different thought process and yes, diagnostic equipment is just as important to contemporary servicing, as it is for repair work. Checking for and downloading software updates, prior to writing them to the relevant ECU, is an important part of most modern car service schedules. Part of this involves not forgetting to reset the service counter. Subconsciously, the dashboard readout (most of which are at least time and mileage dependent) reassures the owner that the service has been done properly. Yet, for an increasing number of models, not resetting the indicator might fail to instruct the  oil condition monitoring system that a lubrication system had been carried-out. This can have implications for diesel particulate filter regeneration, which could cause consequent blockage – a condition that may be blamed (incorrectly) on the filter, rather than an incorrect servicing procedure. 


Any ignition system will experience natural wear and tear but neglect will have deeper ramifications. Bosch’s aftermarket division warns that spark plugs, which are overdue for replacement, will increase their voltage demands and this accelerates wear levels on the coil(s). 

Faulty, or wet, spark plug leads can have the same effect. An engine misfire, under heavy load, can not only cause the coil to overheat (because it cannot release the energy it has built) but unburnt fuel can also enter the catalytic converter, the result of which can be the melting of its expensive, precious metal-coated structure and subsequent destruction. NGK adds that, while most spark plugs do not require their gaps checking and adjusting between replacement intervals, do not neglect the procedure, where it is specified, on older vehicles. Consider also that, unless specific LPG spark plugs are fitted, re-gapping should be added to the maintenance schedule, for a vehicle that runs on gas. Tim Howes of NGK Spark Plugs Technical Service advises that: 

“If the coil is mounted directly on the plug, the coil would need removing to gain access to the spark plug, giving the opportunity to check visually for perishing, or contamination of the rubber contents, corrosion, cracks and evidence of current leakage ‘tracking’. Use the correct specialist tools when removing and refitting ignition coils, in order to prevent damage to the insulating materials, circuit boards, windings, connectors, etc.” 


While most spark plugs tend to be pre-gapped for a specific application, NGK recommends that you should double-check that the gap is correct, before fitting, using a wire gauge to reduce the risk of damaging the precious metal tips of the delicate electrodes. 

Bosch adds, when installing a new spark plug to a GDI engine, you will need to pay attention to the washer design that seals the plug body against the cylinder-head. Should the spark plug possess a solid washer, rather than a crushable one, the engine requires ‘orientated ground electrode positioning’. This means the ground electrode should face away from the injector spray pattern, otherwise the combustion will be incomplete. Bosch argues that for this type of engine and spark plug design especially, a torque wrench is an essential spark plug installation tool, because it is the only way to ensure the ground electrode’s correct positioning. 

For ignition coils, Bosch Aftermarket advises that you should check for the presence of grease, or powder, within any rubber boot that comes into contact with the spark plug ceramic body, otherwise the two materials can fuse together over time. Additionally, check that the engine wire harness is fixed securely to the primary connector for each ignition coil. 

Standard Motor Products Europe (SMPE) highlights that technicians should be wary that ignition coils can be damaged easily by careless fitting. For example, certain types of rail coils, fitted to GM vehicles, can warp and crack, should their fixing bolts be tightened beyond the official 8Nm torque. 


Naturally, poor servicing techniques can damage ECUs, which can be expensive and time-consuming to rectify. Christian Planting, Technical Manager at ACtronics, recommends an external means of battery support, because losing power during the software updating process can damage engine management ECUs. This is because existing data has to be erased during the updating process. Should the power be cut, while data for accessing certain components is deleted, you may not be able to communicate with the ECU, after power is restored. 

While Christian reveals that neglected spark plugs (including inappropriate gapping) do not tend to damage the ECU directly, the ECU’s internal actuators may try to compensate for poor engine running that could result in a broken driver chip. The ECU is more at risk from the fitting of low quality ignition coils, which is known to cause the ignition drivers within the ECU to fail. Christian also advises caution for any work that involves disconnecting the battery: 

“If you disconnect the battery incorrectly you might introduce voltage spikes. This can cause software to fail, because normally, the integrated circuits that contain the software are sensitive to these spikes.” 


Batteries provide the opportunity to offer extra services and to upsell. Check the battery’s state-of- charge (measured in volts) and charge it externally, if required, as part of an extra service. Yet, its state-of- health (measured in amps) gives a real indication of battery condition, when you compare your figure with the Cold Crank Amps (CCA) figure stated on the battery label. You can then advise the customer whether, or not, a replacement battery will be needed before the next service is due. 




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