MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - petronix ignition wiring

Hi all,
I just received a distributor DM2 with petronix ignition (Ignitor)
Came out of an MGB70
There was included a small box (see picture)
Can somebody explain where those wires have to attach to?
Do I need the small box with wires, or can put in the dizzy without it
Iím going to put it in a MGB73
Correct me if Iím wrong
Red and black from distributor to coil , but where ?
Small box:
Black wire = earth
Purple wire to coil , but where
Red wire to ?????
And what about the bleu black and red wires on the small box
A lot of questions, I know, but is it possible to help me
Regards
Raf
rv raf

Raf. No photo attached, so hard to be sure what you have. A Lucas DM2 distributor was used on the MGA and other vehicles of that era. The Lucas 25D4 and the later 45D4, 45DE4, and 45DM4 distributors were used with the MGB. Not sure what you have and cannot provide advise on how to hook it up. A photo would help, but will not change the fact that your distributor was never intended for use in an MGB.

Les
Les Bengtson

Les
Tnkx for the fast response
Have a problem with oploading the picture
to large
will post tomorrow
regards Raf
rv raf

Hi ,
Took some time to upload the picture....
Hope it's OK
Regards
Raf

rv raf

Hi Raf,
My Pertonix Ignitor looks like the part attached to your distributor, with only two wires as shown attached to the component in the photograph.
Are you sure the other component is part of the Ignitor?

Regards
Terry
T J Malloch

That looks like a Lumenition Optronic unit to me, which has a separate optical trigger inside the distributor, the switch for the coil being in a separate unit. A pertronix is wholely self-contained and within the distributor, with just two wires going to the coil terminals.

It depends on what is actually inside the distributor, as they could have sent you a distributor with a Pertronix plus a defunct box from an earlier system. Should be easy to tell, the Optronic trigger is optical and has a shutter wheel on the cam, the Pertronix is magnetic and has a magnetic ring on the cam.

Pertronix *do* have red and black wires, the red going to the coil +ve which should have the white on it, and the black going to the coil -ve that should have two black white wires originally. One of these is to the points and would be redundant, the other is the trigger wire for the tach and should be retained.

The external box could also be a Lumenition rev limiter, which looks to come in the same sort if ribbed alloy box.
Paul Hunt


"Pertronix *do* have red and black wires, the red going to the coil +ve which should have the white on it, and the black going to the coil -ve that should have two black white wires originally. One of these is to the points and would be redundant, the other is the trigger wire for the tach and should be retained."


Paul,
I thought the white wire on the coil went to the tach and the black/white was to the distributor (points) as you stated...... where does the second black/white which you said is the trigger for the tach terminate? On my 67, the black with white is only from the points to the coil? Perhaps I am misunderstanding.....(not unusual for me with electrics...) Ralph
R Stegs

Up to an including 1972 the white comes via the tach pickup from the ignition switch to the coil SW or +ve, the single white/black goes from the coil CB or +ve to the points. It's the current pulses in the white that trigger the tach. From 73 to 74 1/2 the white comes direct from the fusebox to the coil +ve, and of the two white/blacks one goes to the points as before and the other goes back to the tach sending voltage pulses to trigger it, this is the system the original poster should have on his 73.

Any distributor that physically fits can be used in an MGb and run, but the curves will vary to some less or great extent. I'm not familiar with the DM2 or the MGA (although I do know that the 123 electronic distributors are interchangeable between MGA and MGB so physically the DM2 must be the same), but if it came out of an 1970 MGB then it will fit a 1973 and work in it, subject to the curve variations.
Paul Hunt

This thread was discussed between 27/07/2009 and 31/07/2009

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.