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PICKING UP THE SECONDARY IGNITION PATTERN USING AN OSCILLOSCOPE

The right diagnostic tools make all the difference when you are working on any car.

In this video, automotive instructor Rick Zeppetini will show you a simple technique for picking up the secondary ignition pattern using an oscilloscope. Oscilloscopes range in price anywhere from $50 to over $1,000, depending on your budget and requirements, but the two-channel scope works fine for this demonstration.

First, just as you would anytime you are working on machinery, protect yourself. Make sure you have proper eye protection (safety glasses) and the correct safety gloves. The tools you will need are a PC, a PC-based oscilloscope, the secondary inductive pickup that comes with the scope, coil on plugs and a clamp on plate that you can easily make yourself. The inductive clamp is clamped around the post that has been welded on to the plate and the clamp is laid on top of each coil to determine which one is misfiring or which pattern is different. This process replaces the old way of connecting the bulky distributor and ignition coils (which many newer cars don’t have.) to your spark plugs.

For cars that are so well insulated that you cannot pick up a signal, instead of the clamp on plate, we build a piece of wire with an alligator clip on one end and a lasso on the other end, with a nut and bolt in the middle. The loop is lasso’d over the bottom of the coil and the wire is run straight up next to the coil so it can be reinstalled into the vehicle because the vehicle must be running to get a reading. The inductive clamp is clamped around the bolt provided and the coil is installed back in the vehicle. Make sure to ground the wire to a bolt on the motor and attach the secondary ignition leads to the bolt. There is a ground strap here too. By grounding this out, you avoid any leakage through the boot and it discharges any spark that could result in damage to you or your equipment.

Once setup is complete, start the engine and you can view the oscilloscope screen and observe the wave form. You will see the firing line, which illustrates how much voltage it takes for the spark to bridge the gap between the electrode and the ground. Next to that is the burn line- shows the period of time it takes for that spark to stay lit to combust the fuel in the combustion chamber. After igniting the fuel, it shuts off and the residual power simply oscillates until it dissipates, which is normal.

Secondary wave patterns can be used to diagnose fouled out spark plugs, bad compression readings and many other issues. Learning this simple technique will give you another great diagnostic tool to get to the root of the problem quickly.

To learn more essential skills to take you to the next level in your career in automotive repair or to explore the world of Automotive Technology or Diesel Technology call J-Tech today (877) 447-0442 today for more information.

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