Measuring Ignition Health is about determining how your Plymouth’s (or related Chrysler Product) ignition system is functioning before you set out on an adventure (or during that adventure).
Three simple measurements you can make in order to feel good about the ignition’s condition or allow you to spot a possible problem before it becomes an engine stopping issue:
- Secondary Peak Voltage (SPV)
- Primary Voltage at Coil
- Primary Voltage at Battery
Let’s discuss the SPV in this first of three parts series on Measuring Ignition Health. The SPV occurs in the wires/equipment between the Coil output and the engine. The condition of the wires & equipment between the coil & engine can affect the SPV along with the coil & voltage to the coil.
Last year’s restoration article on the Sun Tester discussed the tool the Colonial Region has for measuring not only Peak Voltage but duration and other characteristics of the Secondary Voltage Curve:
This article however concerns measuring only the SPV with a simple, portable, and easy to use tool. Knowing the Peak Voltage can verify if things are normal. One analogy is to compare what you do to check someone’s health using a thermometer placed in the mouth; if the measurement is outside of the normal range then there is reason for concern. The same goes for the SPV for your Plymouth’s Ignition Health.
Knowing the SPR Normal Range for your Plymouth is the first step. Since the SPV varies not only with year & equipment that has crept onto your Plymouth over the years get a measurement when your Plymouth is running well, at normal operating temperatures, and other normal weather conditions. Just like 98.6 degree F might be your normal operating temperature at that body location (and not after a jog in the Park) your Plymouth has a normal Secondary Peak Voltage ; maybe it’s 5,000 Volts for the older Plymouth with a points type ignition and 6 volt original coil. Armed with that knowledge you can compare all future readings to 5000 Volts to determine if your Plymouth is deviating from the norm.
One detail is important; always measure the SPV at the same location with the same instrument. Best location is on the coil wire about 4 to 6 inches from the coil.
One made in North America instrument that is extremely portable, compact, and easy to use is shown in this video:
https://www.youtube.com/watch?v=Gfl1PddWf2g
The battery powered instrument measures SPV and RPM of any 2 or 4 cycle motor up to 12 cylinder.
What if you see the SPV climbing or lowering from the norm? What to suspect? We will cover that aspect in our next article on SPV interpretations.
Remember your first step is to get your Plymouth’s normal SPV at the coil wire 5 inches downstream from the coil.