Ignition question

[Sharpish]

So I put a Petronix coil in the Midg. An earlier post said I have to put the original connectors off the Lucas onto the Petronix. It seems to be running fine with the leads connected straight to the coil as it was out of the box. My tach doesn't work anyway, so is it necessary to put the old connectors on? Am I missing something?

 

[Dozuki]

As long as you can get the necessary connections onto the coil, that is all that matters. Moving the connectors over to the new coil might make it easier to fit the connections. If it works you're set. Just label the Tach wire in case you get a workig tach later (if you didn't hook this wire up).

-D.

 

[dklawson]

This is a footnote to the tach issue.

If your tach is an RVI (current sensing) type, you are not likely to make it work with any electronic ignition system. The later RVC type tachs (that use a single wire connection to the ignition system) work much better as they sense voltage pulses.

 

[Bruce74B]

[ QUOTE ]
This is a footnote to the tach issue.

If your tach is an RVI (current sensing) type, you are not likely to make it work with any electronic ignition system. The later RVC type tachs (that use a single wire connection to the ignition system) work much better as they sense voltage pulses.

[/ QUOTE ]

When did the change occur at MG? Are you saying my tach won't work when I convert my conventional to electronic ignition? It is a 74 incase you can't tell by the handle.

Bruce /ubbthreads/images/graemlins/cheers.gif

 

[dklawson]

I'm not sure when the change from RVI to RVC took place but it probably was before 1974. Look carefully at the face of your tach and you should find (along with serial/model numbers) the letters RVI or RVC. I have heard of a couple of Smiths tachs that had no labeling but this seems to be the exception, not the rule.

RVI tachs have an induction loop either on the back of the gauge OR inside the case on the last ones. They are wired one of two ways depending on the British car they're installed in. The wiring for the induction loop is located either 1) between the ignition switch and the coil, or 2) between the coil and distributor.
See the following links for images:
Early RVI, https://www.mgcars.org.uk/electrical/rv1_1419.html
Late RVI, https://www.mgcars.org.uk/electrical/rv1_1433.html
RVC, https://www.mgcars.org.uk/electrical/body_rvc1410.html

There are always exceptions, but most of the people I've discussed this with have had problems or no luck at all getting RVI type tachs to work with electronic ignitions. The RVC tachs are much more like a current, new, aftermarket tach and connect to the coil with a single wire and sense voltage pulses.

 

[Bret]

[ QUOTE ]
So I put a Petronix coil in the Midg. An earlier post said I have to put the original connectors off the Lucas onto the Petronix. It seems to be running fine with the leads connected straight to the coil as it was out of the box.

[/ QUOTE ]

Reading your profile you have 79 Midget. I’ll admit that I ain’t an expert on Midgets, but I think they originally the same CEI ignitions setup that you find on the late model MGBs (75-80) like mine.

If that is the case your Midget should have the 45DM4 dizzy has an external electronic amplifier that is normally mounted under the coil on MGBs - not sure about Midgets. Anyway that Amplifier has two wires going to the coil. If these are the two wires you are referring to, then you can disconnect them as they are not required with the Pertronix ignition upgrade. I just disconnected mine and tucked them out of site - should I ever want to re-vert back to the stock ignition setup.

[ QUOTE ]
My tach doesn't work anyway, so is it necessary to put the old connectors on? Am I missing something?

[/ QUOTE ]

By this I assume your tach didn’t work before the Pertronix upgrade – so I think you have other issues there. Removing the two wires I am talking about from the Amplifier assembly won’t affect the tachometer. However if you wish to leave them connected is shouldn’t hurt either. I just disconnected mine as the amplifier isn’t used anymore with the Pertronix.

Hope this helps?