MG Car Repair: 1976 MGBGT Engine will not start, air gap, lucas unit

Question
QUESTION: I have a problem with my MG.  It worked fine for a while and then stopped.  I am not getting any spark when I turn over the engine.  However, when I return the switch to the stop position I momentarily get a spark.  The car is has a Lucas type 45DE4 distributor on it.  I reset the clearance on the pickup air gap t0 .014 in. resulting in a much hotter spark but still it will not start.  I don't know what else to do?

Do I need a new ignition-start switch?

Thanks

John

ANSWER: Hi John,
If you have power at the coil with the ignition on an also when you turn the key to start, then you probably have a bad ignitor if you have already set the air gap. Turning the key on and off and getting a single spark is a normal indication of a failed ignitor and all you can do is replace it as there are no repairs that I know of that can be done to them.
Howard

---------- FOLLOW-UP ----------

QUESTION: Howard:

Thanks for your answer.  I have one more question.  Where is the ignitor located?  Is it part of the distributor or the coil? I did notice when I used my test light to locate the trouble it was brighter when the key was in the start position than in the run position.  Is this normal?

Also, do you think I need a new ignition/start switch?

John

Answer
John, the power comes direct to the coil when in the "start" position and it comes by way of a resistor wire when in the "run" position so what you see is normal.
The ignitor is the large box on the distributor that supports the vacuum advance unit. This was an Opus Lucas unit and most died before the car was out of warranty. It is unlikely you are still operating with that unit. What most people do is purchase an aftermarket ignitor (mounts inside the distributor) and they just clip off the three wires to the Opus Lucas box but leave the box on to support the vacuum unit. Some go the the trouble of replacing the distributor completely with a pointed distributor usually a 45D4 although I think any MGB distributor will fit. Your 45DE4 was the Opus Lucas unit. Most of the MG parts suppliers in the US handle aftermarket ignitor units.
Howard