Auto Service Professional

FEB 2018

Magazine for the auto service professional

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12 | ASP February 2018 Technical Coil-on-plug technology An overview of COP technology and diagnostics tips By Bill Fulton A t the risk of dating myself, I can remember the good old days of distributor-equipped engines with external coils and a coil wire to which we could conveniently attach our scope's second- ary KV probe. And by using our number 1 trigger, we could sort out each individual cylinder's firing characteristic (see Figure 1), enabling us to detect lean cylinder conditions, rich cylinder conditions, low cylinder com- pression problems, high secondary firing KV demands, insufficient spark duration periods or any type of a density misfire. Now on modern day engines equipped with COP-type ignition systems , access to all the diagnostics of reading and analyzing a secondary ignition waveform creates a challenge and the need to be creative. Creative simply means using a second- ary KV wire between the coil and spark plug and attaching our secondary KV probe to the wire and analyzing the single secondary ignition waveform. e necessity of under- standing the secondary ignition waveform still exists. e diagnostics that were yielded to us on distributor- equipped engines are still available using this method on COP-equipped engines by viewing a COP secondary ignition waveform (see Figure 2). e critical part of these second- ary ignition waveforms is the spark line in reference to length, angle and the presence of turbulence. Lean conditions will shorten the length of the spark line and bend it upward and increase the turbulence, the same as the distributor-equipped engines. Remember air molecules are non-conduc- tive, which increases the voltage demand of the spark line to ionize them. Notice, however, the length of the spark line on COP ignition systems is significantly longer in duration simply because we only have the Coil-on-plug, or COP, features an individual coil dedicated at each cylinder, with the COP con- nected directly to the spark plug, eliminating the need for plug wires. Due to variances in COP design among auto makers, spark control, troubleshooting and diagnostics can vary. This article is intended to provide education relative to COP, along with tips and precautions regard- ing testing and diagnosing engine misfire issues. Figure 1 Figure 2

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