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MG MGB Technical - Earthing of MGB engine

Hello,

I have just tried to start my MGB for the first time since major overhaul and I can hear the starter relay switching but no movement of the starter motor. How is the engine earthed? Should there be an earthing strap or is it earthed through the engine mounts?

Many thanks,
Alex Davies

There should be an earthing strap on the engine mount to bypass the rubber. Try running a jump lead from the earth battery terminal straight to the engine.
c cummins

Alex. As noted, the chrome bumper MGBs earthed through a braided strap from the engine to the frame and attached to the front engine mount. (Right hand side from memory.) The rubber bumper MGBs earthed through a similar strap that bridged the transmission mount and ran from the tranny to the crossmember. (Again, on the right hand side as I remember it.) A jumper lead from the battery to the engine, as suggested, would work. So would a jumper lead from the engine to the frame. In either case, the jumper lead is from one half of a set of jumper cables or some form of similar heavy duty wire.

If the ground strap is missing, the system will try to ground through the throttle cable and, perhaps, the choke cable. This will overheat the parts and may quickly result in damage to them.

Les
Les Bengtson

Thanks, I have done what you suggested and connected an earth directly from the engine (well starter motor actually) to the negative terminal of the battery.

However the starter motor will still not turn over when I turn the key. I can hear the starter relay switching but no action from the starter motor. I am also getting 12V from the starter relay to the starter solenoid. Is there anything simple I have missed?

Many thanks
Alex Davies

Alex,
It sounds like the classic low battery.

For the future - you might think about putting the ground lead somewhere you can see both end - mine is cylinder head (3.9) to inner wing. I clean off the battery neg to chassis regularly too.

HTH Roger
R Walker

Checkout the battery condition and connections then jump it assuming the engine will actually turn!!!!
Allan Reeling

A bad earthing strap will still usually allow the solenoid to operate, or chatter at least, and the motor to try and turn the engine. You will get hot heater, choke and accelerator cables.

A bad battery, or battery connections, will usually cause the ignition warning light to dim right down.

A meter between brown at the fusebox and the engine show both of the above, between brown and a body earth will show you which.

A click from the relay and nothing else implies a disconnection through the starter relay contact to the solenoid, which could be 12v missing from the relay, bad relay contact, white/brown bad connection to relay or solenoid, or open-circuit solenoid winding.
PaulH Solihull

This thread was discussed between 18/01/2012 and 19/01/2012

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