10 replies to this topic

[Mowie]

Thought I was ready to start the engine in the car but have been having some issues. On the ignition switch, my coil wire only gets partial voltage 0-4.9 then in the On/Run but full 13 when in start. 
 

Looking at the LX Torana wiring schematic it appears two wires from the switch converge at the engine harness connector. Was this the mechanism to get the power at run and start? I’ve only got a single.

The car has a EZ wiring harness kit, I have it wired up per the photos of another switch on here. Top is neutral safety switch, middle is power in, left is accessories, centre ignition and right is coil.
 

Have I got something wrong or is the switch buggered.

 

Thank you

[76lxhatch]

The original wiring had a yellow wire that delivered full voltage while cranking, and a large pink resistance wire that dropped it for normal operation once running (in the ON position). To facilitate this there are two separate circuits in the ignition switch itself. You can bridge these to get full power in both positions, provided the wiring is suitable. See the ignition switch connector on the right side of the wiring diagram to determine which terminal is which.

[yel327]

As above, pull the ignition switch out and solder a wire between the start and run blade terminals right down at the base (so the plug goes back fully onto the switch). The terminals are the ones that the pink and yellow wires go to on the plug.

[axistr]

Only modify the coil feed wire to 12v if you have an electronic distributor. If your still running a points distributor you will need to retain the ballast resister circuit or you will quickly burn out the points. It was common to see a white aftermarket ceramic ballast resister fitted back in the day. Check to make sure there isn't an aftermarket resister already fitted inline with the original pink wire which could be giving you the low voltage reading. 

[Bigfella237]

Also, there are 12 volt coils and there are lower voltage coils (around 6v from memory?). You need to fit the correct coil for the application.

 

If the wrong coil is fitted it will probably still run, but a 12v coil that's only getting 6v will have a weak spark, and a 6v coil getting 12v will overheat.

[yel327]

Only modify the coil feed wire to 12v if you have an electronic distributor. If your still running a points distributor you will need to retain the ballast resister circuit or you will quickly burn out the points. It was common to see a white aftermarket ceramic ballast resister fitted back in the day. Check to make sure there isn't an aftermarket resister already fitted inline with the original pink wire which could be giving you the low voltage reading. 

 

Excellent point! I (possibly incorrectly) assumed the OP was trying to feed a 12V coil.

[Proto]

There isn't anything wrong, it is how it is designed. You get full 12v to the coil during starting, however this isn't required during normal running & it drops back to the reduced voltage once the eng is running. Assists in service life of the ignition system. High performance applications, may have a need for the full 12v at all times.

[yel327]

It is a very common mod and has been since the 80's, for people to put HEI distributor and coil out of an XT5 or the following VK and VL engines into anything with a GMH red 6 or V8. Those need the full 12V to the coil at all times.

[Mowie]

Thank you all for the feedback, I should have elaborated more. I’m using the coil wire as a continuous 12 volt switched to trigger the ecu and the cdi box. 

 

I stupidly thought the coil would be 12v in the on and start positions but didn’t check, then was dumbfounded when I had no ecu or spark.

[Bigfella237]

I've never used one of those EZ wiring harness kits but I'm surprised it didn't give you the option to use the resistor wire or not?

 

Either way, I would never power an ECU directly from a rotary contact switch (like the ignition switch). Every factory EFI car will always have at least one relay powering the ECU & coil(s) with voltage direct from the battery, with the ignition switch simply activating the relay.

 

Depending on the relay used, it may be quite happy to operate at the reduced voltage too?

[Mowie]

Hi Andrew,

 

The ecu and cdi are both powered with direct attachment to the battery via fuses, just using the 12 volts as the trigger to have them on.

 

Tom