Welcome to our resource for MG Car Information.



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 GT V8 Factory Originals Technical - MGB V8 wiring

Hello Everyone,

My Engine is in and I am having problems.
I have a 1978 US MGB with a Buick 215, accel electonic distributor, GM alternator and a gear reduction starter. All the electrical worked prior to pulling the original motor.

Now after reading numerous posts and pages this is what I have done so far.

The gear reduction starter has two posts instead of three. I am going to bypass the ballist so I did not hook up the little white and green wire to the starter. GM alternator was hooked up according to one of the conversion pages I found on the net.

I have not hooked up the coil or distributor as of yet. I tried to turn the engine over and it seems to work great (nice sound with the gear reduction starter). Problem is that the fuel pump is not getting power. Also the alternator seems rather warm to the touch.

Also, another page said that if you are bypassing the ballist resistor that you should run a wire from the fuse box where the wire wire connects to the positive side of the coil. Well, there is no wire wire connected to my fuse box.

So I guess my question are:
1. Is the starter hooked up correctly without the white and green wire?

2. Do I have to wire up the coil and distributor in order to complete a circuit for the fuel pump?

3. Which fuse box post should I use to hook up the positive side of the coil?

Please forgive my rather lengthy post. I have consulted the haynes manual and I am sure that most of you know that there is just enough information in that book to allow one to mess something up.

Thank you all for all of the valuable information that you all have posted on the BBS. It has been a great help thus far.

DJB Biddix

By the way, my email address has changed from the one listed with this post. It is now Thank you
DJB Biddix

Fuel pump problem has now been fixed. Cracked wire within the harness. Thanks Everyone
DJB Biddix

The starter will work fine without the light-green/white. If you still have the 6v coil you *must* retain the ballast, and without the light-green/white connected to the starter you will not get the coil boost voltage when cranking, which can make starting difficult under adverse conditions. However you can add a relay which replicates the function of the missing boost contact on the starter.

If you have a 12v coil you connect the +ve terminal direct to the white terminal on the fusebox, which should be the 2nd one up at the front. If you have an ignition relay (a 78 should have) there will be a white/brown at this point. In this case you should connect the coil to the white at the ignition relay, as connecting it to the white/brown you may well find that when you turn the ignition off the engine will continue to run. In either case you are bypassing the ballast, which makes the boost circuit (light-green/white) uneccessary, but again you may get starting problems under adverse conditions.

6v coils generally measure about 1.5 ohms at the primary, 12v standard coils about 3 ohms, 12v sport coils about 2.4 ohms. This is how you determine what coil you have and hence whether you need to retain the ballast or not.

The alternator should *not* be warm simply during cranking. If it is it implies it is passing a large current just with the ignition on, or possibly with it off, which indicates a fault. This could cause serious damage to the alternator or wiring.
Paul Hunt

This thread was discussed between 30/12/2004 and 31/12/2004

MG MGB GT V8 Factory Originals Technical index

This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.