• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Ignition / Coil Wiring Question

Share this page

G

Guest

Guest
Guest
Offline
First off: Newbie here with a 1980 B

Related pix: https://www.scaledatacom.com/mgb/

The car has what I think is an electronic ignition (noted in Pic 3). I think this is a replacement as my car has the taped-off group of wht,wht/blu and wht/blk wires that other folks have which indicates the original elec ignition was swapped out for this newer one.

From this ignition box are 5 wires:
red goes to + on coil
black goes to - on coil
purple is ground
bundle of 1 wht and 1 blk wire go directly into distriubutor.

There are 2 connectors that I think were nudged loose by me while futzing in the engine bay but I'm not 100% sure and don't want to connect them if they're not supposed to be conncted. Pic 5 illustrates this.

Basically, I'm trying to figure out if the wht/grn wires should be conncted to the the wht/blk wires given the current ignition setup the car has.

Thanks in advance for any help!
 

Attachments

  • 188615-wires5.jpg
    188615-wires5.jpg
    36.7 KB · Views: 131
Jamie,

Given that someone apparently "cut-in" an aftermarket electronic ignition kit, it's kind of hard to tell exactly whats going on but here's my try. Refering to your attached diagram, the green/white wires were originally part of the ballast/resistor/coil/solenoid wiring loop. On one side of the ballast/resistor was the wht/blue and the other side was the white wire that connects to your cut-off wht/green wire. The connector you show in your diagram on the two wht/green wires originally went to + terminal on the Coil. Do you have a wiring diagram? If you don't - Get one ASAP. Also from your attached pictures I dont see the wht/Blk wires connected. Does your Tachometer work? The wht/black wires originally connected to the negative terminal on the coil - one controls the Tach the other goes to the distributor. Of course that's how it was originally. Hope this helps!! 77blueblunder
 
I remebered that the white/black wire goes to the tach, but not where it originated.... It'll be time for an oil change soon... I may snap a pic then.
 
You also need to look at the coil. The original coil was a 1.5 ohm and required the use of the ballast/resistor. The way yours is wired the ballast/resistor system has been bypassed. You may have a 3.0 ohm coil. In any event as long as the car runs good with the electronic ignition that is on it, I would only be concerned with hooking up wht/blk wires to get the tach working.
 
Looks like one of those units that Whitney used to sell. How about a photo inside of the dizzy, with the rotor out? /ubbthreads/images/graemlins/crazyeyes.gifPJ
 
77BlueBlunder, I do have a wiring diagram but my car doesn't match up because of this cut-in system.
The car isn't running as I'm waiting to see if the wht/blk wht/grn wires should be connected. I didn't want to start the car and have something fry.
I'm pretty sure the wht/blk wire group wasn't connect to the coil the last time the car was running as the wires were no where near the coil when I started working on it.

The question is: should the group of wht/blk be connected to the wht/grn group (where the 2 red question marks are)?
I think they may have been connected last time the car was running but I think I nudged them loose while futzing in the engine bay as few weeks back. Or, could I do any damage by connecting the wht/blk group to the neg on the coil and the wht/grn to the pos on the coil given there is a new ignition setup now?

Thanks all...any info is more than I have /ubbthreads/images/graemlins/smile.gif
 
Jamie,

How long has the car been sitting?

Since the car will not run, looking again at your diagram, it does not look like you have any power going to the coil. Try connecing the white/green wire connector to the + side of the coil and the wht/black connector to the - side. Pull one of the spark plugs and have someone turn the engine over while you ground it against the block. Do you have a Spark? if so that is good. Replace the plug and try to start.

If not, connect the cut wht/grn wire to the cut white wire you show in the taped bundle. Try the spark plug test again. If you have a spark now you can replace the plug and try to start the engine. If this doesn't get you going send me an email. /ubbthreads/images/graemlins/hammer.gif
 
ummm... all but one plug in a hole is asking for a facefull of problems. It'll START on three holes firing...

I'd say sit with a VOM and find hot leads with the iggy on, figure which goes to coil. Purple ground sounds like a...umm... "X700" someting-or-other solid state system. Not a bad way to go, but: using voltages and ohms is a more prudent method that "spinnin' 'er up" with parts of the system still connected. A good diagram is kinda helpful too. If memory serves, there is a white wire to the tach, not a white/black. That indicates a "trigger" circuit.

...where's that bloody PDF when ya need it....
 
Yea your'e right about the one plug out . I thought about that after I sent it. better to use a spark tester or pull all of the plugs.

I did check the stock wiring diagram the wht/blk does go to the tach. There's a good PDF wiring diagram on the Advance Auto Wire web site.

thanks for the correction.
 
THAT's the PDF I was huntin'. EARLY car here, white to tach as an induction pulse, and couldn't find th' reference quickly. Good on ya!
 
Hi Jamiebo, I think the GRN&WHT wires connect to the BLK & WHT ones. However, this still leaves the ignition circuit unpowered. It would seem necessary to connect the Ballast resistor which is by passed by the blue and white wire to the NEG terminal of the coil.-Fwiw--Keoke-AZ- /ubbthreads/images/graemlins/cowboy.gif
 
Car was running perfect a month ago...then I swapped out battery, main battery positive cable (old one was crapola), changed oil, filters etc...Now car will turn over but not start. I think I nudged some of the wht/grn and wht blk wires from their prospective connections while under the hood and don't know where to connect them now.
I've been told by some to connect the wht/blk to the neg on coil and wht/grn to pos on coil...and others say they none of them should be connected to the coil and should all be taped off.
Figure 5 in this Lucas diagram closely resembles my config:
www.scaledatacom.com/mgb/diagram.jpg

In the diagram, wht/grn are taped off and not used...which makes me wonder: where is the coil getting power from?

Any help/recommendations would be great. she turns over but will not fire up.
 
That is my concern also there is no power to the coil as shown. I took a good look at the second drawing you provided and if that agrees with your configuration it seems to me to be correct. If you have an Ohm Meter measure the resistance of the coil, if it is much greater than 1.5 Ohms,say about 3ohms the PO may have replaced the coil with an unbalasted one and starting may still be a chore if wired as indicated in the second drawing---Keoke

Check it out and let us know how you get on
 
Back
Top