TR6 Ignition Switch Question

[SherpaPilot]

Greetings to all my Triumph friends. After a little less than a year, I have finally installed my freshly rebuilt engine into my 72 TR6. All the subsystems seemed to go back on without problem with one little exception, my ignition switch. During the engine rebuild, I repainted my empty engine bay and of course had to reinstall all the wiring etc. It seems that my ignition switch now turns the engine over nicely but during the engine's rotation (during the start) no power is being sent to the coil. After the spring-loaded switch return to the "run" position, it then that the engine starts and all is normal. I hope this makes sense to someone. I'm sure I have missed a connection somewhere along the way but can't seem to figure this one out. I plan on going through the wiring diagrams tonight but thought someone may have a quick answer for me. As usual, thanks for any input. Don

 

[bobhustead]

Check the wiring diagram. There should be a wire going straight to the coil from the solenoid when it is engaged. Otherwise the starter draw parasitizes all the juice.
Bob

 

[SherpaPilot]

Hey Bob, Thanks for the response. My wiring chart shows a white wire from the fuse block going to the + side of the coil. The - side of the coil also has a white wire going directly to the spade on the distributor. I'm not showing any direct connection to the starter or alternator. I plan on tracing each wire for connunitity to assure they are correct. Your comment concerning the starter drawing all the current makes perfect sense but I do not see any current protection offered to the coil during the start sequence. I'll keep plugging away at this. Thanks again for your help. Don

 

[poolboy]

The schematic has it right, power from the ignition switch to the white wire side of the fuse for the green wire circuits and from that white wire side of the fuse to the positive terminal of the coil
In other words the coil gets 12 volts when the ignition key is in the START and in the ON/Run position.same as everything on the green wire side of that fuse.
If you have that wire from the fuse block to the coil, but no start when you twist the key to START maybe the problem is at the ignition switch

 

[bobhustead]

I just looked at the diagram and was going to posit a problem in the ig switch, too. But it looks like the white that powers the ig switch is in constant unswitched connection to the white that goes to the fuse box and thence to the coil. It appears there is no shunt like I suggested and power supply to the coil should be the same whether the switch is energizing the white/red or not. Makes no obvious sense to me, but Ken almost has to be right on this and the problem is the ig switch.
Bob

 

[bobhustead]

Just for the fun of it (fun not my first choice of words), try a supplemental jumper wire from battery pos direct to coil in and see if it starts during cranking instead of just when you let off the sprung ig switch connection.
Bob

 

[bobhustead]

In the feed to the ignition switch, there is a device (dunno what it is) shown on the diagram that has brown/yellow going in and white coming out. Possible fault in that device that keeps sufficient current from coming into the circuit to properly power white and white/red simultaneously?
Bob

 

[poolboy]

That's the IGN light on the dash tachometer

 

[SherpaPilot]

Bob, Ken, Thanks for your expert help on this. I'll try that jumper wire from battery over to coil. A new ignition switch is probably a good idea. I have been reading wiring diagrams every chance I get and it is driving me crazy. Now I know why I'm not an electrical engineer. Thanks again, guys.

 

[poolboy]

Assuming the green wire components,such as the fan motor and windshield wipers work when you turn th ignition key to ON you should make that jumper to the coil from the white wire side of the fuse that protects the green wire circuit...otherwise if you directly use the battery, the coil will always be fed voltage even when the ignition key is OFF and when you want to stop the engine the only way to do it will be to remove the jumper from the battery.....AND if you do decide to use a direct connection to the battery, make sure the connection to the battery is the last to hook up and the first to disconnect....less sparking like that.....but go to the white wire side..that's the way to do it.

 

[bobhustead]

Ken
I intended the jumper to be a one time temporary test to be abandoned as soon as the test is thru.
Bob

 

[SherpaPilot]

Bob, Yes, I knew what you were suggesting with the temporary jumper. I will get back to trouble-shooting this problem sometime today. I plan on doing a complete grounding check. I'm hoping I don't need to get into that ignition switch replacement. I know it is quite an involved job. But I'll do whatever it takes.

 

[SherpaPilot]

You guys will not believe this but, problem solved. I spent the day checking out grounding mounts; Nothing helped. I decided to bite the bullet and order up a new ignition switch but before I did, I pulled an old spare coil from my parts inventory and swapped it out with the existing coil. All of a sudden everything worked like it should. Who would have guessed a coil would fail like that? As far as I'm concerned, all is normal once again. Thanks once again to all of you guys who suggested ideas to look into, yout help is appreciated. Don

 

[bobhustead]

I guess I can see how current deprivation by the starter load might be the cause, but it would be great if one of our EEs could explain it. I would NEVER have guessed the coil.
Bob