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MG MGB Technical - 67 GT Electrical Gremlin

67b GT Positive ground. While driving recently warning light comes full on, lose electrical tach, fuel gauge and wipers (not sure about lights as it was day). After driving for 5 or so minutes car began to run badly due to lack of fuel (pump was affected too?). Stopped waited 5 minutes then she started back up as was fine. Happened again next day and several more times as well. Have checked all connections at fuse box and regulator, generator and battery. All seem fine. Have done a bit of wiggling of wires but to no avail. Suggestions? Have followed threads here (and else where) with no solid solutions.
Thom Fox

Check ALL of the connections to the body including the ones under the dash, in the boot, and the engine ground strap.When a lot of electrical gremlins show up at once it is likely to be due to a poor ground.
John H

The warning light will only come on when there is a voltage difference betwen the dynamo and the battery. I suppose it could happen that the battery circuit disconnects and the ign current is drawn from the dynamo via the warning light. The coil is fed from the dynamo side of the ignition switch. I had a very similar fail minus this sympton once which was an open 3 way bullet connector in the loom on the RHS looking forward where the loom goes across in front of the firewall.I lost the tacho but pressed on, a short while after passing the School Bus from Penn School where Jane works the car spluttered to halt as the fuel pump had stopped as well and I had to admit that this did rather spoil the effect.
Stan Best

Normally if the warning light comes on with the engine running it means that the 12v supply through the ignition switch has been lost, and is usually accompanied by the engine stopping. But there are three white wires coming off the ignition switch on a 67 - one feeds the fuel pump, tach electronics and fusebox (and through the fuse to the wipers and fuel gauge), a 2nd feeds the ignition warning light, and the 3rd feeds the ignition via the tach pickup. So I suspect that the first two whites became disconnected from the ignition switch which caused the wipers, tach, fuel gauge, and fuel pump (and hence eventually the engine) to fail and the warning light to glow, but the 3rd remained connected allowing the engine to continue to run until the carbs emptied.

Check the whites carefully where they connect to the ignition switch.
Paul Hunt 2

This thread was discussed between 19/10/2006 and 20/10/2006

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