The electronically controlled variable dwell ignition system has been fitted to many makes and models of vehicles world wide. This system was first introduced in the WB Holden and the VC Commodore. It is a very popular ignition conversion for the older Holden red engines. A small modification to the ignition supply voltage is all that is required to convert over to this system along with using the correct ignition coil.
The distributor incorporates an induction type pulse generator that forms the basis from which the on time of the dwell angle is determined by the control module. This system is commonly known as a variable dwell system to the ones that know. To others it is just an electronic ignition system. This system allows a higher primary current to pass to the ignition coil, creating good intensity, combined with a long duration spark, to achieve greater total spark energy throughout the entire RPM range.
The ignition coil used for these systems is specifically designed to cope with the variable dwell operation and requires 12 volts to the positive side of the coil to work correctly. The special coil has greater primary and secondary windings as compared to points type coils, and would burn out points if used in such a system. Original versions used either an oil filled design (and looked similar to points coils, but sometimes employed a male high tension tower), or were of a transformer design. The HT leads also needed an upgrade to handle the spark output and hence 8mm HT leads were used along with larger spark plug boots.
When these systems first hit the mechanics workshops, we were very weary of being shocked by the high voltage spark created. We used to remove HT leads from spark plugs while the engine was running by grabbing the boot end of the lead and if we got a shock it was no big deal. However if we did the same with the electronic system and received a shock you would definitely know about it. Most dealerships were warned not to remove the leads without using the appropriate tool. Photo below of the tool I used to remove HT leads from the spark plugs regardless of ignition system type. I have been bitten many a time because the HT lead spark plug boots had degraded and lost their insulation ability.
Photo on left is the correct position of the tool on the boot. Photo on right is incorrect position.
In the following video I cover how to remove the module & service it to attain a longer life.
In Part 2, I cover the centering of the stator assembly.
In Part 3, I go through a NO START scenario using a flowchart I created
I have created a diagnostic flowchart for a No Start situation where the ignition system is at fault. Use it as a stand alone or in conjunction with the Part 3 video of the series.
No Start Diagnostic Flowchart.pdf
Have you considered converting over your old Holden to electronic ignition but are not sure how to do it. This document shows how to modify the electrical wiring so that 12v is supplied to the coil. The distributor module will still work without the mod, however the variable dwell control will not, so it is necessary to carry out the mod for correct operation of the module. Also do not forget to fit the correct ignition coil to match the distributor otherwise you may damage the module.
Bosch Electronic Coil Specs.pdf
