Triumph Repair: 79 Spitfire Ignition help, engine cranks, color codes

Question
QUESTION: Hi Howard,

I was correcting some of the odd wiring and ignition set-up from the previous owner on my 79 Spitfire. I found the pink/white resistor wire for the coil was showing copper at various places so loomed it with some tape. I removed the coil and Lucas amplifier box and pulled the harness out to do so. Solenoid is hooked up again correctly and the engine cranks just fine.

I also removed a green wire that the previous owner installed to the + side of the coil from a white wire near the alternator. I traced that white wire to the main harness in the cabin, but I don't know what it's for. The previous owner was using it to feed power to the coil and the white/yellow wire (which is supposed to go to the coil) was cut. I'm getting 12v with the ignition switch on from the white/yellow wire and from the mysterious white wire. You're test procedures from previous posts say that the white/yellow wire should not get any power when ignition is on.

I also don't know where the ignition amplifier is supposed to be mounted. The previous owner had it mounted underneath the coil at an angle with one bolt going through. I know it's not the exact way to mount it. I also need to know which wire (white/black & white) goes where. I forgot to take a picture of it before removal and it doesn't show up in any diagram.

This car was a bit of mess when I bought it, but so far I managed to sort out most of it.

Thanks.

ANSWER: Hi Michael,

I often received cars to work on even back in the 70's that had wires changed so I had to ignore color codes as they are not reliable on cars that have had someone changing wiring and now that these cars are 30+ years old you must check the function of a wire and forget what color it is.

The amplifier on your car (if it is a US model) is mounted on the distributor with the vacuum retard unit mounted on the amp. The distributor should be a Lucas 45DE4. This was called a "Opus/Lucas" system and was so prone to failure that very few even made it out of the one year warranty without being replaced once or more times. So many failed that several aftermarket manufactures started making replacement ignition systems.

The pick-up in the dist was hard wired with three wires into the control unit. The control unit on the dist was powered by a power resistor mounted on the engine.

The way that it operated was that when you turn on the ignition to "Start", power was supplied to the 6v coil from a small pin on the starter solenoid. This supplied 12v to the 6v coil but due to the amperage draw of the starter motor the available voltage was not full 12v. But plenty to fire a 6v coil. As soon as the engine started and the key was released back to the "IGN" position, the power was disconnected by the starter solenoid. Now power was supplied to the coil by the ignition switch through a resistor (usually a resistor wire). The Amp itself was always powered by it's own power resistor mounted on the engine.

Most owners by the time they had to pay for the failing Lucas box replaced the pick-up in the dist with one of the many available aftermarket control units which were so small that they were put in place of the old pick-up unit and the three wires to the box were just cut. The box needed to stay, as it supported the vacuum retard unit. The system was rewired as per what ever aftermarket unit called for. Most owners and mechanics didn't bother worrying about color codes. So most cars ended up with a unreliable color code.

In your case you need to first determine what ignition system you have. Then you need to find out what wiring (if not Opus/Lucas)is required for that system. Some aftermarket systems continued to use the 12v bypass system and a resistor wire to power a 6v coil. I seen some that did away with that system of the bypass and put a 12v coil on the car and others even switched the distributors.

I went to the extremes on a TR-7 (with the same system) and installed a points cam in the dist and mounted a set of contact points in mine. This was a lot of work and I don't recommend it. Not because of points but because of all the work required to do it. I am not against electronic ignition nor for it. I am happy with either one.

Howard

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

QUESTION: I know of the ignition setup that you speak of, but it doesn't match the Lucas amplifier I have. What I have is separate black box (it says Lucas on it) with two holes going through it for mounting and blue and red wires connected to the distributor and two white wires (one with a black tracer) to the coil.  Is it possible that Lucas made a replacement distributor and amplifier? I read on a forum that the amplifier might not be getting a good ground. I want to note that I had this same setup on my TR7.

I should also note that the coil is a 12v coil. I did notice the voltage drop of the white/yellow wire at the starting position as well as the mysterious white wire I mentioned earlier that was rigged to the coil.
Should I switch out the coil for a 6v one?

Thanks again.

ANSWER: Hi Michael, send me the Lucas part number so maybe I can trace the system down. I never seen a system like that on a Spitfire nor a TR-7 and I have owned a half dozen TR-7s and worked on many Spitfires. You are in the US?

Howard

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

QUESTION: The part number is AB14. I was able to get the car running again. I managed to find an old picture I had of the engine bay and got a close up of the coil connections. I have the correct connections now. I bolted the amplifier back to where it previously was and it started right up. I guess the amplifier case does need a ground.
 
Yes, I am in the U.S.

Thanks for the help.

Answer
Michael, I am glad to hear that you were able to figure out how to wire it and get it working. the AB14 is a model type, not a Lucas part number and as far as I can find was never installed on a Spitfire. It could have been a replacement for the Opus/Lucas system. It is the type used on early 80's Jaguars and is very reliable on them. If you open up the box, you will find a GM moduale inside.

If it fails on you, open the box and take out the GM moduale and match it up at most auto parts stores for about $35. as opposed to purchasing a new Lucas unit for over $300. As I remember I didn't find an exact GM number match but was able to match it up and it works.

Howard