Wiring

[chrisfell]

Here's an odd one. I was routing around in the dash wiring, trying to locate which if the many white wires from fuses 6 and 7 was the one that fed the fuel pump. Interesting to note that none of the white wires are fuse protected. Even more interesting was that once I'd found the wire for the pump, the alternator/ignition light was also disconnected. Not quite sure why, but it was almost certainly due to the decision by a PO to fit a modern alternator with built in regulator, rather than the OEM items. Said PO was a retail E-Type specialist, now no longer retailing E-Types.

So now I have a hidden fuel pump switch and a tell tale on the dash!

BTW, the car starts and everything else works when the pump is disconnected. Except, of course, the engine rapidly dies as the carbs empty of fuel.

[cactusman]

Cool.....that is what you want...

[mgcjag]

Good oppertunity to also fit a seperate fuse for the fuel pump

[chrisfell]

Good oppertunity to also fit a seperate fuse for the fuel pump

I assume there was a reason why the fuel pump and the ignition had no fuse in the first place. Anyone any ideas what that reason might have been?

[abowie]

. Interesting to note that none of the white wires are fuse protected.

White wires bring power from the ignition and are before the fuses. Green wires are fused; these come from the opposite side of the fuse block to the white wires. So power comes to the fuseblock in the white wires, goes across the fuse and then leaves via the green wires.
The fuel pump gets power from a white/purple wire. This is supposed to come off fuse 4 however it often comes off fuse 6 or 7 with all the green wires.
The ignition light is probably disconnected because whoever did the conversion couldn't get it to work properly with the alternator.
Hope that helps.

[mgcjag]

Hi Chris.....we will never know Jaguars thinking.....was it cost saving, or just poor design........a goog design today for a distributed electrical system is to fuse as close to the supply as possible.....this will protect the wireing.....then fuse individual components....just look at your house system......re Andrew above...not completely correct.....unfused white does come from the ignition to one side of fuses 6/7 and then through the fuses via green wires to various ccts....but on the input side of fuses 6/7 there are other whites that are unfused, one goes to the fuel pump, tacho (ignition) etc.....one white does have an inline fuse (heated rear window)......

[PeterCrespin]

Hi Chris.....we will never know Jaguars thinking.....was it cost saving, or just poor design.......

Ah yes, the old "They were incompetent, or cheapskates" schtick.

The truth is they were complying with the formal British Standard for car wiring. BS something or other.

So did every other UK vehicle maker in period AFAIK, including those notorious skinflints like Rolls Royce, Bentley and Armstrong Siddeley. Which is good, because it means you can troubleshoot any British car in period by knowing which colours go where, without a wiring diagram.

Unless you are one of the 11 percent of colour-blind men, like me. Did anyone else here make crystal sets and transistor radios etc. with those Philips Electronic Engineer kits when they were kids? Mum got fed up of answering my questions on resistor band colours, but then it's the females that pass on colour-blindness genes without suffering from it...

[mgcjag]

Hope Jaguar havnt kept the wireing "as factory original" in their reborn project......designer/engineers knew about fuses in the 60s.....you cant use that old chestnut of thats how it was done in them days....they were just doing what every one else was......after all they pushed the boundries with the IRS.....why not do the same with the wireing......

[64etype]

Hi Chris.....we will never know Jaguars thinking.....was it cost saving, or just poor design.......

Ah yes, the old "They were incompetent, or cheapskates" schtick.

The truth is they were complying with the formal British Standard for car wiring. BS something or other.

Seriously? A British Standard said white wires shall not be fused?

Regarding changes to the factory restorations, JCNA concours types are already complaining that they might not have the proper BEEs or GKN hardware, and have frowned upon improvements or upgrades to the original specification for the appropriate model year.

[mark10337]

I think what was meant is the BS Standard said White wire represent unfused switched connections.

[Puddinhead]

I'm currently working on my "66 FHC (LHD) and I see the White B+ wires to the #6 Fuse post. I assume that the battery current flows un-fused through the Alternator 4TR relay and then onward to the #6 fuse (?) Just a few days ago I mistakenly fried my working 4TR and now of course, no dash red light. Anyone know who rebuilds these 4TR units ? My fuel pump is non-working, so if it's non-working due to perhaps a dead short, would the failed shorted fuel pump draw enough battery current to melt the entire wiring system. When I get a new fuel pump, II will wire in a specific fuse for the fuel pump.

Thanks,
Patrick
'66 FHC (LHD)

[rfs1957]

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Quote :

How many of us, I wonder, realise that all the white wiring under the dash is live yet unfused, and that includes the ignition/coil feed ?

Yes, I'm relieved to see that the live-white-wire-syndrome didn't affect just me.

As I wrote at the time in 2014 - " I'd welcome any observations about potential unexpected side-effects of what I've done, and why - perhaps - what I perceive as shortcomings in the original fusing may have been deliberate, though after several hundred kilometers (read thousands, now in 2017) with these changes active everything behaves as it should ; sleeping above where the car lives as we do here, in a country where building-regulations, fire-doors etc have not yet percolated down, I'm happier to know that everything is now sitting behind a fuse, and that - to the uninitiated - things look undisturbed and original."

Since then I've also fitted a battery cut-out switch in the earth cable, with a 2A fuse jumper across it for the clock and interior lights.

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