Ignition Coil Wires Reversed?

[Funracer]

While Tony is recalibrating my WUR I decided to replace my old, possibly original Bosch red top coil with the MSD 8222. I have a cold idle miss that goes away when things warm up.

I have had my 83SC for about 9 months now and have never touched the ignition coil wires. I disconnected the old one today the white wire was on the (-) side terminal and the brown wire was on the A terminal. According to my Bentley they should be the other way. The MSD has + and - terminals so I guess white to positive and brown to negative.

Would the car have run ok since I bought it like this or am I off my rocker? Would it have damaged the CDI?

Don’t want to start the car until I verify the proper connections, and don’t have the WUR anyway.

As an aside, not much in the Bentley about the ignition coil. Maybe I looked in the wrong chapters.

[Trackrash]

1 is - and is the ground.

[ed mayo]

The polarity at the spark plug is reversed if the coil connections are reversed. current will flow from the ground electrode to the center electrode, that isn't desirable since electricity doesn't flow as well from a cold surface to a hot surface.

[John at J&S]

MSD supplies a -500v pulse to the coil positive, and a ground to coil negative. The output from the coil tower is then negative high voltage.

With inductive ignition, coil positive is 12v, and the negative has a 400v positive pulse. The result is a negative high voltage from the coil tower.

[Funracer]

Haha you guys are killing me.

So the bottom line. For my new MSD 8222 coil, white to +, brown to -.

Correct?

If so that would be the opposite of how mine was connected to the Bosch

[John at J&S]

Key off, remove both wires. Use your ohm meter to determine which one is ground. Connect that one to coil negative.

[cab83]

Hi Funracer,
Bosch coil on my 83SC has brown on 1, white on A as shown in attached photo.
Hope this helps,
Bill

[Funracer]

Now you guys are talking on my level.

Mongo love pictures.

Thanks

[smadsen]

I've had the 8222 coil on my '82SC for at least 12-15 years. The white wire has been on the + (positive), the black on the - (negative) the whole time. Prolly 80,000 miles (of the 246,000 total). 'Course it still could be on bass-ackwards, but the car runs great.

Then again, if I reverse them, I might find another 50 horsepower amid the smoke & sparkle.

[cab83]

Also, if you're interested in selling the Bosch black coil I may be interested. I've been looking for a coil with a 3 digit (34x) date code on it. You may PM me if selling.
Thanks, and best wishes with fixing the miss..
Bill

[cab83]

Bentley for 911SC, Section 970-9: WHT to A, BRN/RED to B

[Funracer]

Originally Posted by cab83

Hi Funracer,
Bosch coil on my 83SC has brown on 1, white on A as shown in attached photo.
Hope this helps,
Bill

Btw, my Bosch wires were reversed from your picture. Yours agrees with Bentley.

[AndrewCologne]

Originally Posted by ed mayo

The polarity at the spark plug is reversed if the coil connections are reversed. current will flow from the ground electrode to the center electrode, that isn't desirable since electricity doesn't flow as well from a cold surface to a hot surface.

You even won't get till there.

The whole electrical flow of the inner CDI circuit will get messed up and the unit could be destroyed (beside this also this could harm the inductive coil in the distributor and also the circuit in the rev counter, means all devices connected to the CDI), as with up to 500 volts out of the CDI, of that risk someone should be aware of, if not then happy barbecuing.

[John at J&S]

No, the CDI doesn't care which end of the coil primary it is driving.

[mysocal911]

Originally Posted by John at J&S

Key off, remove both wires. Use your ohm meter to determine which one is ground. Connect that one to coil negative.

Neither pin on the coil should be connected to its case (ground). If so, then the coil is bad. Furthermore, most won't notice
any difference in the engine's functioning by having the wires reversed.

[John at J&S]

Determine which WIRE is ground. Connect that wire to coil negative.

Waste spark ignitions, like the the Electromotive, have half the plugs firing backwards.

[Funracer]

Originally Posted by cab83

Bentley for 911SC, Section 970-9: WHT to A, BRN/RED to B

Yes I saw that as well, thanks. Not much else in Bentley about the coil.

[AndrewCologne]

Originally Posted by mysocal911

Neither pin on the coil should be connected to its case (ground). If so, then the coil is bad. Furthermore, most won't notice
any difference in the engine's functioning by having the wires reversed.

He meant the 31 terminal from the vehicles ground which provides ground to the CDI and ... the Coil (not to its case but to its "-" terminal.

[mysocal911]

Originally Posted by AndrewCologne

He meant the 31 terminal from the vehicles ground which provides ground to the CDI and ... the Coil (not to its case but to its "-" terminal.

If you want to be totally technical about the coil polarity with regard to the Bosch CDI pulse, then the positive pin of the coil
should be grounded as the CDI produces a negative going output pulse.

[John at J&S]

Not if you want the voltage to the plugs to be negative.

For CDI ignition, a negative pulse on coil positive makes a negative pulse at the coil tower.

For inductive ignition, a positive pulse on coil minus makes a negative pulse at the coil tower.