Secondary Ignition Test Procedures
To quickly check Secondary Ignition we recommend the following:
Testing Secondary - Ignition Using a Labscope
· If the labscope being used has an adjustable Sample Rate, use the faster setting. The control for sample rate speed may be called Acquire or Acquisition or Spike Detect or Peak Detect, or some similar name.
· Fast sample rate is important when testing any signal that has a spike associated with it, such as secondary ignition, fuel injectors, and alternator ripple voltage (when a problem exists).
· Use the manual or normal trigger setting rather than AUTOmatic setting if possible.
· When triggering on the Firing Line, position the trigger voltage level so that it is always higher than the highest point of the spark line.
· When testing a Distributor Ignition System it is possible to view a parade pattern as well as individual cylinders.
- PARADE – Set the time/div to 10 ms.
This setting will allow sufficient time across the display to show all the cylinders in a parade pattern, if necessary raise the
RPM enough to have all cylinders showing on the display screen.
- INDIVIDUAL CYLINDERS – Set the time/div to .2 ms or .5 ms.
These settings will allow only enough time to display the event being triggered.
Move the trigger pickup lead to each ignition wire one-at-a-time to see each individual cylinder.
- If the Secondary Ignition waveform appears upside down –
Activate the labscope INVERT feature or, if possible, reverse the capacitive test lead connections at the labscope.
· When testing an ignition system that uses one coil to fire two plugs, the technician can connect a single ignition test lead clip to one ignition wire-at-a-time and diagnose each individual cylinder. No trigger pick-up lead is used.
- Because of the polarity issues involved in this type of secondary ignition system,
half of the wires will show upside-down waveforms. Activate the labscope INVERT feature or, if possible, reverse the capacitive test lead connections at the labscope to have the up-side down waveforms appear right side up.
- Look for spark line duration to be a minimum of 1 mS. - Spark line must not drop to ground.
Ignition Coil - Secondary Resistance
Using a DMM
1. Disconnect connections to Ignition Coil.
2. Set meter to measure Ohm's "Ω".
3. Connect the black COM lead probe tip to the secondary terminal.
4. Connect the red Volts/Ω lead probe tip to the coil positive terminal.
5. Most specifications call for several thousand Ohms - verify the specifications for the specific coil you are testing.
· Infinite resistance reading means an open circuit.
The most complete testing of Secondary Ignition involves using a labscope. Labscope
testing will reveal problems in the plugs and ignition wires as well as cap/rotor and coil wire.