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| Joined: | 07-15-2013 |
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Welcome to the wonderful world of Lucas electrics. If it is any consolation, I am an electrical engineer, have played with electronics since I was 12 and have owned British roadsters for over 40 years and the electrical problems still drive me nuts.
First off, if you do not have a multimeter, get one. It does not have to be anything fancy as long as it has AC and DC voltage, current and ohm functions. You will also probably need some extension cords with clip leads long enough to reach around from the engine compartment to the cockpit. You will sometimes need to be able to clip the meter to a ground point as well as to the point being tested in order to make a measurement while trying to start the car.
The biggest problem I have run into is bad electrical connections. Even worse is when they are only sometimes bad. It sounds like this is what you have. First thing is to examine all the connectors in the circuit that is not working. Over time, the connectors become loose, corroded or dirty, making the connections unreliable. Also, the wires going into the connectors also become frayed and break as they are removed and replaced.
You will need wire clippers and wire strippers as well as a crimping tool to replace any of the connectors that look bad.
With the ignition turned on, you should get about 9V-12VDC at the +V connection (not the Hi voltage connector) of the coil, depending on whether there is a ballast resistor in the circuit. When you crank the engine this voltage should be 12V if the ballast resistor bypass circuit is working. When you crank the engine you should get close to 12VAC at the connection between the coil and the points (or hopefully an electronic ignition module). If something is not showing up when it should, you can use the ohm function to find where the bad connection is.
Sorry if this is stuff you already know. I was not sure how knowledgeable you were, so I thought it best to start with the basics. I will check back and give more detailed info if needed.
Tom