UK Car Repair: 76 MG midget 1500 - No Spark, spark plug wires, vacuum unit

Question
I am new to midgets to bare with me. I have always thought the they were pretty neat cars so i figured I would buy one and restore it. I found a 76' 1500 that a guy had lost interest in so i took it off his hands. When i got it the engine turned over strong but was not getting spark. I have since drained and cleaned out the gas tank and fuel lines, replaced the coil, spark plug wires and coil wire, and spark plugs. After all of that, when i hooked up a test light to the wires and plugs i was still gettin no spark. Every so often I would get a very faint and inconsistent spark but thats about it. I then hooked my test light to the coil wire, inbetween the wire and the distributor. I then noticed something very odd. I would turn the key and the engine would begin to turn over. No matter how long the engine would turn over I would get no spark. When I turned the key off I noticed a quick spark in the test light. This happens evey time. What could this possibly be? any ideas? Any help would be great. Thank you very much in advance.

Answer
Josh,
You probably have an Opus-Lucas ignition system. The way to ID it is look at the distributor where the vacuum advance unit is attached. If the vacuum unit is mounted on a box attached to the dist. then it is an Opus-Lucas. This system has a very high failure rate and is not repairable. The single good spark when turning the ignition off is a common symptum of a failed unit. There are several aftermarket ignition systems available. You will have to keep the box as it supports the vacuum unit. Just clip the wires and install the new unit inside the dist. Directions will come with the new unit. Look at the box to see if the wires have already been cliped, if so it is an aftermarket unit inside and it has failed. The only thing you can do is check the air gap between the rotor and the pick-up unit. It should be about .015 in. You are suppose to use a non-ferris feeler gauge. (a paper match book cover is about .015 in.)
"Moss Motors" and "The Roadster Factory" are sources of MG / Spitfire parts. That is a 1500 Spitfire engine.
If you don't find them on the net, let me know and I will look up their URL addresses.
Good luck
HMF