Bodywork, Paint, Interior, Trim, & Wiring

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timsgolf
Timothy Smith

(7 posts)

Registered:
01/15/2023 03:05PM

Main British Car:


Coil wiring
Posted by: timsgolf
Date: January 15, 2023 03:09PM

1967 AH 3000 BJ8 MKIII
Modified with chevy 327 v8 engine & 4 speed muncie transmission.

The car died while driving today. Stone cold dead. No response at all when turning the key. Lights work.

Popped the hood & saw one coil wire had come loose & fallen down onto the exhaust manifold, where it had melted & welded itself there. (See pics)

I pulled it off, but can't locate the proper attachment point. Note the flat female style wire end. It seems there should be a flat male style somewhere that it pulled or shook loose from, but I can't seem to locate it anywhere. Can anyone advise?

Tim
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Edited 2 time(s). Last edit at 01/15/2023 04:09PM by timsgolf.


DiDueColpi
Fred Key
West coast - Canada
(1372 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Coil wiring
Posted by: DiDueColpi
Date: January 16, 2023 12:22PM

If that wire had a dead short then it has very likely blown a fuse. I'm assuming it's fused, but not positive as it's non stock wiring.
As a WAG I would suspect that it goes to the I terminal on the starter. This provides full power to the coil when cranking.

Cheers
Fred


timsgolf
Timothy Smith

(7 posts)

Registered:
01/15/2023 03:05PM

Main British Car:


Re: Coil wiring
Posted by: timsgolf
Date: January 17, 2023 09:24AM

Thanks for the response Fred. That makes perfect sense. As a matter of fact its one of the first things I thought about - especially noting the flat terminal end on the wire. Two things ended up having me rule that out however.

(1) the starter is situated too far down below for this wire to reach. Stretching it I got it down to within about 3 inches of the starter.
(2) The wire would have had to defy gravity - fallen upward - in order to land on the exhaust manifold.

This failure happened right at dusk on Saturday evening. I was trying to get it figured out before Monday afternoon when I had an appointment with the mechanic to install some front end parts that had recently come in from England. Since I didn't get it sorted, I towed the car to the shop yesterday. As soon as I'm able to talk to the shop I'll post the solution on here.

Tim


DiDueColpi
Fred Key
West coast - Canada
(1372 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Coil wiring
Posted by: DiDueColpi
Date: January 17, 2023 02:20PM

The only other possibility that comes to mind would be power for the choke heater.


timsgolf
Timothy Smith

(7 posts)

Registered:
01/15/2023 03:05PM

Main British Car:


Re: Coil wiring
Posted by: timsgolf
Date: January 17, 2023 07:58PM

Thanks again Fred.
Regardless, it seems to me you're right about the ignition circuit side of the fusebox being blown. I should know more tomorrow.
Tim


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6472 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Coil wiring
Posted by: BlownMGB-V8
Date: January 18, 2023 10:12AM

That erosion on the corner of the spade connector indicates a strong chance that it was arcing before the fuse blew.

Jim


timsgolf
Timothy Smith

(7 posts)

Registered:
01/15/2023 03:05PM

Main British Car:


Re: Coil wiring
Posted by: timsgolf
Date: January 23, 2023 07:33PM

Jim,
The corner of the connector is not erosion - it fell onto the hot manifold and soldered/welded itself there. I pulled it off.



timsgolf
Timothy Smith

(7 posts)

Registered:
01/15/2023 03:05PM

Main British Car:


Re: Coil wiring
Posted by: timsgolf
Date: January 23, 2023 07:36PM

Fred,

The car repairs are not yet finished - the front end parts are installed and it is now at the alignment shop. I did speak to my mechanic today however and got a partial answer. You were not wrong Fred. There was a blown fuse on the ignition circuit somewhere. They replaced the fuse and left the loose wire unconnected. The car started and ran fine. When it gets back from alignment tomorrow they will track down the attachment point. The cooling fan is a later add-on - and has nothing to do with starting/running, so I'm suspecting it might be the culprit. Will know when I pick it up!

Tim


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6472 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Coil wiring
Posted by: BlownMGB-V8
Date: January 24, 2023 09:48AM

Tim, that spade terminal is made of sterner stuff than solder, that corner was not melted off. If it had been it would be a blob at that point and not the jagged missing edge that you see there. You MIGHT get that from long term rubbing against a hot and rough surface like a cast iron manifold but it is much more likely to have gotten that way from electrical discharge, sort of like you might see in an EDM machine only without benefit of the oil. That's why I say it was eroded. Being a loose electrical wire that is the most likely and since you say there was a blown fuse, even more likely. Probably the car was running with that wire in light contact with the header, and it occasionally arced across depending on movement from vibration, each arc taking out a little metal until it got the way it is and at some point making contact long enough to blow the fuse and stop the car.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(4526 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Coil wiring
Posted by: MGBV8
Date: January 24, 2023 10:02AM

Agree with JIm. When I first saw it, I thought it was electrical arc damage.


timsgolf
Timothy Smith

(7 posts)

Registered:
01/15/2023 03:05PM

Main British Car:


Re: Coil wiring
Posted by: timsgolf
Date: January 24, 2023 08:54PM

You guys may be correct!

The final opinion is that this is truly a mystery wire! Seriously, the mechanics never found where it was supposed to have been attached. Consensus is that it was not attached anywhere on the other end - just lying up in there and eventually vibrated its way free, shorting on the manifold and blowing a fuse. Everything works. Even the addons - fuel pump, cooling, fan, radio. Don't ask me why the terminal end was still connected to the coil!

The wiring in general, but especially under the dash and fusebox, is a total mess. Apparently when the engine swap was done years ago, they didn't replace the old fusebox, they added a second one! Wires are going everywhere - jumping from one to the other, etc... It was highly recommended that we go ahead with new wiring. I agreed to it. The new wiring harness was placed on order today and should be ready in 5-6 weeks. I knew this was coming but wasn't thinking I would do it this quickly. What I wanted to do is replace the dashboard, center panel, glovebox, and trim, etc... at the same time we did the new wiring.

The only dashboard replacement options I've seen (ahspares & moss) are the woodgrain. Does anyone know if there are any other options out there? Maybe somebody does custom work in this area?

Thanks again for all the responses,
Tim


MGBV8
Carl Floyd
Kingsport, TN
(4526 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Coil wiring
Posted by: MGBV8
Date: January 25, 2023 09:39AM

Here's a WAG. It was meant to be a temporary wire to a tach used under the bonnet for tuning. :)


timsgolf
Timothy Smith

(7 posts)

Registered:
01/15/2023 03:05PM

Main British Car:


Re: Coil wiring
Posted by: timsgolf
Date: January 26, 2023 09:09AM

Hmmm... good theory Carl!


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1165 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Coil wiring
Posted by: ex-tyke
Date: January 26, 2023 02:05PM

For whatever reason, I thought that it might, at one time, have been for an electric choke..


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