Cut-off switch / Battery in boot

[lanciamad]

As the subject suggests, i'm trying to fit the battery into the boot as well as fitting a cut-off switch. I had some issues with the electrics where one minute 8v was being supplied to the fusebox/ignition and then 12v, I seem to have cured that with replacing a dodgy wire/connector as well as taking off and refitting components, checking connection etc... I thought i'd turned into god where 12v only arrived when I got into the car and then 8v as I stepped out
As the car is originally, I have no problem with fitting the cut off switch and have had it working like that etc... so thats fine, but when fitting the battery in the boot it doesn't wana know. See diagram below:

Brown wire is in fusebox on battery side, so to cut the ignition by the cut-off switch.
My initial thoughts was this should work, but it doesn't. Everything is fine, but when the ignition is turned on there's some kind of noise coming from the coil area and the rev counter is irratic, if you try to start the car the ignition goes dead. I am presuming this is down to everything being taken off of one thick main wire coming from the positive terminal, but I don't see how that differs from having it coming off of the battery terminal, there all connected at the positive terminal anyway.
My question is, if I run a seperate wire from the positive battery terminal to power the fusebox/red/yellow wires will that solve my problem? Great if it does, but just a pain because i'll have two cables running side by side through the whole car.
Only other thing is, does the airflow meter need to be earthed for any reason, as its attached to the battery tray, and isn't when I put the battery in the boot.
Thanks in advance to anyone's help/thoughts and yes i'm mental to modify beta electrics, before someone says, "just why"  

[thecolonel]

PM or email me your phone number and I'll talk you through it (Diagram does not make sense)
airflow meter as far as I remember is on bolts through rubber grommets so not earthed.

Geoff

[lanciamad]

Well I ran it past, an ex automotive electrical technician and an electrician to see if they could shed any light on the situation but couldn't see anything wrong with how i'd done it. IE, the same setup as it was in the front. I had two last idea's to try, before contacting you Geoff, 1. being run a seperate wire for the red, yellow and cut off switch wires, (which I think tbh has no effect)
2. in a mini like fashion, fit a wire between the gearbox and the chassis, this is what was needed.
The earthing from the engine/gearbox to the chassis was obviously not good enough, meaning that when you turned the key for the starter, the ignition would just go dead and no starter motor. I've now fitted a cable from the gearbox to where the battery tray bolts to the chassis, all cleaned up back to metal, and it started first time and runs fine, job done
If anyone ever wants to do the same it can be done, quite easily just remember to earth the engine/gearbox to the chassis via an additional wire. Pics / basic diagram available on request.

[thecolonel]

Well done on solving the problem.

Most common problem on any car is often an earth fault.
The Gamma has bolted/soldered earths on most circuits, including two on the engine/gearbox
which eliminated 95% of the previous faults (poor lights, odd starting, really weird charge cycle etc)

if you can always solder any connection rather than crimp connectors and never ever use scotchblocks

Geoff