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MG MGB Technical - Problem Coil

My 1966 mgb roadster has always run ok until now .
I have a problem all of a sudden with the coil . The car will not start at all . The only way I can get it to start is to disconect the cables coming out of the loom to the points side of the coil and running a new cable to the distributor .

There are for whatever reason two yellow cables comimg out of the loom that got to the points side of the coil and then one running to the dissy .

Can anyone tell me what these two cables are and where that go to.

What seems to be happening is with these two connected when you turn the key its taking power away from the coil.

Any ideas on a fix . the car is positve earth .

Many thanks
Carl Suthenwood

Sorry guys i dont know if i have a ballast risister or not . Manul says no . If i have how do i by pass if i need to .

Thanks
Carl Suthenwood

Carl,

If you are saying that there are 3 wires on the low tension coil terminal that goes to the dissy, that doesn't sound right to me. I thought there was only one wire, and that it went to the dissy. Do you have the original style ignition or has some electronic version been added?

Charley
C R Huff

Thanks Charley no there are 2 coming from the loom then 1 going to the dissy

thanks
Carl Suthenwood

As far as I am concerned it is all origiginal and worked ok last year

Thanks
Carl Suthenwood

Sorry Carl. I'm still not getting it. Where are the two wires coming from the loom attached. Are they attached to the same terminal that has the wire to the dissy or are they attached to the other terminal?

You might try going to www.advanceautowire.com and downloading the wiring diagram. It shows a wire from the tach to one side of the coil and then a wire from the other side of the coil to the dissy.

Charley
C R Huff

Carl,
Someone has been messing, replacing wires etc. If you are pos earth, you SHOULD have a white wire, which is ignition switch live, to the neg/sw side of the coil and a white/black to the pos/points side, which goes to the dizzy, through the points to earth. The white should be live/12v only when the ignition is on. If you have the white and white and black, leave the yellows off and see what happens . If the yellow are to the neg/sw spade on the coil it's possible they are supposed to supply the switched live, but why two???????. Put a meter or bulb etc., on the yellows and see if they are ignition switched live. If the yellows are additional wire It is possible that someone has added an anti-theft device earthing out the low tension circuit. This circuit will go through a hidden switch, to earth.
Allan Reeling

Allan X2

Herb
Herb Adler

Come on Carl, we do like to know the outcome!
Allan Reeling

If the points wire from the coil has to be disconnected at both ends, and a new wire run in before it will start, the existing points wire must be shorting to earth. If you can leave the existing one in place and adding a new one also allows the engine to run, then the existing one is open-circuit.
Paul Hunt

This thread was discussed between 14/05/2013 and 22/05/2013

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