wires on twin cam special near carburetors

[analogmike]

1974 Twin Cam Special US spec

Does anyone know where these wires go? I pulled my carburetors off to get them rebuilt and trying to clean up things below it.   I searched all the manuals and wiring harness diagrams but could not figure this out. 

the first picture is a device on the carburetor side of the engine bay just below the emissions plaque. The brown wire which appears to be a hot wire connected to the starter is not connected. I just don’t know what this device is, or if I should reconnect the brown wire.

The second picture shows two yellow wires (circled) coming out along the suspension arm, one of them goes back and into the harness by the right rear tail light. The other yellow wire seems to have been chopped off so I’m not sure where that second one goes or what it does

The third picture is the coil and there’s another yellow wire with a large connector on it that is not connected.

any help is appreciated!

[4129R]

There is a wire which goes from the starter solenoid to the coil, which gives 12v to a 9v coil,  only on starting. If you have a 9v coil, the + side of the coil is attached to a wiring going to a wire wound resister on a white ceramic body close to the coil, which reduces 12v ignition to 9v when the engine has started. I believe the wire from the starter solenoid to the coil is white with a red trace.

The relay is not standard Lotus wiring that I have ever seen on any TC or TCS.

[analogmike]

There is a wire which goes from the starter solenoid to the coil, which gives 12v to a 9v coil,  only on starting. If you have a 9v coil, the + side of the coil is attached to a wiring going to a wire wound resister on a white ceramic body close to the coil, which reduces 12v ignition to 9v when the engine has started. I believe the wire from the starter solenoid to the coil is white with a red trace.

The relay is not standard Lotus wiring that I have ever seen on any TC or TCS.

very interesting, I will check that out. It does seem like that’s a problem I have, it’s sometimes very hard to start the car, it doesn’t want to start until I turn the key back to run position in then it might fire up.

[analogmike]

https://www.facebook.com/share/r/1B9K4NiZSb/?mibextid=wwXIfr

you can see from the video that I figured out what the wire was that was detached from the square electrical box. I believe it sends voltage to the starter solenoid. Makes it really easy to make a remote starter!

I did some checking and measuring and I don't seem to have the resistor that lowers the voltage to the coil. When the car is running the coil has a full voltage on the plus side and about half voltage on the minus side (which I guess is because the points are opening and closing). I tried to see where that disconnected wire at the distributor attaches to - it does not attach to power or the starting circuit. I didn’t check to see if it is attached to the wire near the starter that was cut off.

The car is running great but it still has a problem starting when hot - it cranks great but doesn’t try to fire until you get off the ignition key and then it has about a second to start or it dies. Maybe my coil is bad, I’ve got all new ignition parts that I’ll be replacing now that it’s running and I know the carburetors are working.

thank you and I hope this information helps someone else.

[4129R]

I have fitted Gold Top 12v coils.

Never had any problem starting from hot, but countless problems starting from cold with 40DCOEs.

[analogmike]

Hi,

I did get the gold coil, will put it on soon.

I could not start the car at the gas station, finally got it going after a dozen tries by letting off the starter and getting the engine to catch as it came off the starter, which was lowering the voltage while cranking.

I found the wiring diagram, there is supposed to be a COLD START COIL (all twin cams in all markets according to the diagrams) which sends full voltage while cranking, but mine is not connected, I think it's the wire hanging by the coil. I traced it and it DOES go to the starter solenoid, but is not sending voltage to the coil. Not sure if the wire is broken or the starter connection is bad or it's not a starter with this feature (or my mechanics hooked the wires up wrong).

The wiring diagrams on europa.com does not make sense, I think they are  drawn wrong. They shows a "cold start coil" but do not show where the coil gets it's normal running voltage from. Also I can't find a tach wire on the coil, may be connected elsewhere in the harness?

Thanks for any help!

[jbcollier]

Some starter solenoids have a contact that is powered when the starter is cranking and is otherwise isolated.  That is the correct terminal to use for a wire direct to the coil.  You can't use the solenoid energize cionnector other wise the it will be powered all the time from the coil.  You can fit a relay that is powered by the WR wire to the starter and then use that to power the coil during cranking.

[4129R]

3 wires by the coil.

white with black trace goes to the distributor from the -ve side of the coil, and earths the coil when the points are closed.

white only is a +12v feed from the ignition switch, and if you have a 9v coil, it goes to one side of the wire wound resistance on a ceramic base, with the +9v power coming from the other side of the wire wound resistance to the +ve side of the coil.

white with yellow trace comes from the starter when the starter is cranked by power from the white with red trace from he ignition switch, and gives 12v to the +ve side of the coil, only when cranking.   

[analogmike]

thank you for the replies.

I confirmed the wire from the starter that was hanging loose by the coil is the cold start wire and it does get voltage when cranking. I did some testing and found that it has the same voltage when cranking as is already at the coil. I noticed a thick brown wire going to the starter was cut off and taped up and there was a (new?) thick grey  wire running forward. you can see the grey wire in the picture showing the starter, the brown wire was in the harness that the other wires come out of.
when cranking I get about 9.6 V at the coil or at the starter so that should be good enough.

I still don’t understand how the tachometer works most of my cars have a wire going from the points connection on the coil to the tachometer. The wiring diagram seems to show a power wire running through the tachometer which also powers the coil. Although my wiring may have been modified. but I don’t understand how the tachometer functions without going to the points.

I replaced the coil with the gold coil, and rotor, distributor cap, and spark plug wires and it seems to start fine now even when warm.

installing the spark plug wires in the distributor cap was not straightforward, the instructions that came with the cap are wrong. They say the screws should only go halfway through the wire, but if you do that there is no connection. I used my meter and turned in the screw until I started getting some resistance and then I kept screwing it further until the resistance went down to the actual wire resistance which is about 16 K. Then I gave it a little more just for safety.

Will be putting in a perTronics points replacement next.

After getting my carburetors rebuilt with the bigger European needles, the throttle response is so much better, the car feels like it’s got 30 more horsepower.

Thanks again.

[BDA]