Technical
Coil-on-plug technology An overview of COP technology and diagnostics tips Coil-on-plug, or COP, features an individual coil dedicated at each cylinder, with the COP connected 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 regarding testing and diagnosing engine misfire issues.
By Bill Fulton
ignition waveform still exists. The diagnostics that were yielded to us on distributort the risk of dating myself, I can equipped engines are still available using this remember the good old days of method on COP-equipped engines by viewing distributor-equipped engines with a COP secondary ignition waveform (see external coils and a coil wire to which we Figure 2). The critical part of these secondcould conveniently attach our scope’s second- ary ignition waveforms is the spark line in ary KV probe. And by using our number 1 reference to length, angle and the presence of trigger, we could sort out each individual turbulence. Lean conditions will shorten the cylinder’s firing characteristic (see Figure 1), length of the spark line and bend it upward enabling us to detect lean cylinder conditions, and increase the turbulence, the same as the rich cylinder conditions, low cylinder comdistributor-equipped engines. pression problems, high secondary firing KV Remember air molecules are non-conducdemands, insufficient spark duration periods tive, which increases the voltage demand or any type of a density misfire. of the spark line to ionize them. Notice, Now on modern day engines equipped however, the length of the spark line on COP with COP-type ignition systems, access to ignition systems is significantly longer in all the diagnostics of reading and analyzing a duration simply because we only have the secondary ignition waveform creates a challenge and the need to be creative. Creative simply means using a secondary KV wire between the coil and spark plug and attaching our secondary KV probe to the wire and analyzing the single secondary ignition waveform. The necessity of understanding the secondary Figure 1 Figure 2
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12 | ASP February 2018
