Primary Wave Forms

The waveform image below, was taken from a dual static ignition system which was suffering from a lack of power, caused by low fuel supply pressure. It illustrates the effects on the ignition 'spark line', when loaded.

No fuel misfire

The wave forms below, represent the ignition primary voltage and current signals, taken from a 206 Gti EW10j4 engine, which had flagged the 'MIL' and recorded the following 'P' code: P0351. (Intermittent fault. 1/4 ignition coil control. Open circuit, short circuit to positive, short circuit to earth). Upon initial 'scope inspection, using just the voltage signal, it was not immediately obvious there was a fault present. However when looking at the current ramp of both channels, it became obvious there was something wrong.



The following wave form shows channel 1/4 with the new coil fitted. There was approximately 0.5 ohms difference between the channel 1/4 primary circuit and channel 2/3 primary circuit.


The wave forms below show the difference between a Sagem coil pack and an Electrofil coil pack fitted to the same engine, (TU3jp - KFW), which has suffered periodic stalling. The Electrofil is coloured blue and the Sagem is coloured red. Not shown is the maximum peak voltage created by these coils, which in the case of the Sagem was 392 volts and the Electrofil 362 volts. Both taken at idle no load and hot.

206 TU3-KFW primary

Primary ignition voltage and amperage, with shorting spark plug. Conventional ignition system, as fitted to a 205 TU3 engine.


Primary ignition system trigger voltage and ignition voltage. Conventional ignition system as fitted to 309 Gti.

primary ignitiondescription

Ignition primary signal taken from a bad Sagem coil, causing Idle regulator motor fault, (Sagem SL96). Wasted spark ignition system, TU5jp.


Ignition primary signal taken from a replacement coil pack on the same vehicle, along with a new ECM. Wasted spark ignition system, TU5jp.


Primary pattern taken from a faulty, individual, coil fitted to a V6 ESJ9, causing a misfire.


Primary pattern taken from a good coil, fitted to the same V6 ESJ9 engine with a misfire.


Last Reviewed: 10 January 2018Copyright © 2004...2018 Mark Stammers