Questioni have a 1980 mgb with electronic ignition, i have no spark, it has a new coil it has power there. i was wondering if the voltage regulator is bad and how to test it its original lucas regulator red wire and blue wire coming out of regulator going to distributor thanks andy
AnswerHi Andy
The Lucas electronic distributor was never fitted to UK cars, so I have only limited knowledge of it.
Before looking at voltage regulators etc, it is worth doing a few basic checks.
1) Unplug the 3-way connector that attaches to the amplifier, turn the ignition on, and check for 12 volts or more at the white wire AND at the white/blue wire. It could just be a faulty resistor in the white/blue circuit.
2) Inspect the carbon brush in the centre of the distributor cap.
3) Disconnect the central wire from the distributor, remove the distributor cap, and hold the end of the wire about 1/16 of an inch above the centre of the rotor arm (using electrical pliers, not your bare hands). Get a helper to turn the engine over using the ignition key. If you CAN see a spark between the wire and the rotor, then you have a faulty rotor arm.
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Looking at my workshop manual for 1980 USA cars I cannot see a regulator. Inside the distributor there is a small pick-up unit known as a Hall Sender. It has 2 wires coming from it that go directly into a box attached to the side of the distributor. These wires are not shown on the wiring diagram, so I don't know the colours. The box contains an electronic amplifier unit and also the mechanical vacuum advance unit. From the box, 3 wires emerge, coloured white, white with a black stripe, and white with blue. The amplifier is a sealed unit made using 1970s technology, and it either works or it doesn't. It is 30 years old, and the manual does not specify any tests for it.
This unit was marketed by Lucas under the name `Opus', and it has a reputation for unreliability. It is commonly referred to as `hopeless'. In particular, the amplifier is very prone to failure when it gets hot, but can often recover as it cools down again.
I guess you could test the Hall Sender, but in order to do this you would have to cut or un-solder the 2 wires that connect it to the amplifier. It is just a small pick-up coil that responds to rotating magnets. An ohm-meter should give you a reading, and so long as the reading is not zero or infinity, the actual measurement is irrelevant. I would set the meter on the 2,000 ohms range and check for a resistance.
If the Hall Sender resistance is open circuit, look for a broken connection or a broken wire. There are no electronics inside the sender, just a small coil, so it should be mendable, or a new sender might solve the problem (if you can still get one).
If you are good with electrics, you could fit an external amplifier, such as the Motorola unit which was fitted to cars such as the VW Rabbit, and connect your Hall Sender directly to it.
Personally, I would install a Pertronix Igniter type LU141. It retails for about $70 and the unit fits entirely inside your original distributor, replacing the Hall Sender. The two wires from it connect straight to the coil. It has a modern amplifier built into it, so it would completely bypass your old (non-functional) amplifier. Full instructions come with the kit.
If I can be of more assistance, feel free to get back to me.
Happy New Year
