Bodywork, Paint, Interior, Trim, & Wiring

discussions about bodywork, paint, interiors, trim, audio, electrical components, wiring, etc.

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88v8
Ivor Duarte
Gloucestershire UK
(1041 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Electric tach fubar
Posted by: 88v8
Date: August 25, 2023 01:31PM

So the second electric tach is fubar.

Needle jumps around, then when I go over 2000 it jumps to max and stays there.

I recall the same happened to the tach in my previous vehicle. The common factor is that it had a Lumenition Optronic (optical) electronic ignition, and the tach was hooked to the coil. I wonder if there is a problem with the spark plugs affecting the ignition - no other sign of that - or upsetting the tach.

Should I change to resistor plugs, or perhaps just on the left bank where the ignition and coil are located, or is it just one of those things...

Ivor


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6470 posts)

Registered:
10/23/2007 12:59PM

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

authors avatar
Re: Electric tach fubar
Posted by: BlownMGB-V8
Date: August 27, 2023 02:16PM

Have you considered using Theo Smit's tach movement driver circuit?

Jim


Moderator
Curtis Jacobson
Portland Oregon
(4577 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Electric tach fubar
Posted by: Moderator
Date: August 28, 2023 01:36PM

Quote:
Should I change to resistor plugs, or perhaps just on the left bank where the ignition and coil are located, or is it just one of those things...

Yes, I'd try resistor plugs. And I'd recommend using the exact same model spark plug for each cylinder.
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88v8
Ivor Duarte
Gloucestershire UK
(1041 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Electric tach fubar
Posted by: 88v8
Date: August 31, 2023 04:54AM

Thankyou.

Theo Smit I guess is here.
No haven't encountered that... electrikery... likely beyond my pay grade.

I bought a Faria tach now, then realised I need to find a way to podmount it as no one makes a 110mm pod for a 4" tach, sigh...

V8


Spitfire 350
Phil McConnell
Perrysburg, OH (Toledo area)
(257 posts)

Registered:
01/11/2010 09:19PM

Main British Car:
74 Spitfire 350Chevy

authors avatar
Re: Electric tach fubar
Posted by: Spitfire 350
Date: August 31, 2023 08:12AM

I made a spacer ring out of a thin piece of plywood and covered it with black felt to mount my tach and speedo in the large stock mounting holes.
20230831_080008.jpg


DiDueColpi
Fred Key
West coast - Canada
(1365 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: Electric tach fubar
Posted by: DiDueColpi
Date: August 31, 2023 01:29PM

I usually just gut the old gauge and mount the new one inside it.


88v8
Ivor Duarte
Gloucestershire UK
(1041 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: Electric tach fubar
Posted by: 88v8
Date: September 20, 2023 01:34PM

Eight new resistor plugs BPR5ES. On a drive today, only 15 miles but still... the tach was OK.
So maybe it was interference with the ignition module.
In which case I have a spare 4" tach :{

I found that NGK are now offering solid-top plugs, meaning the little wotsits don't unscrew. This is good, unless one is running a vintage, as I have several times found a misfire due to the wotsits undoing themselves, and had to affix them with threadlock.
Not all progress is bad.



MGBV8
Carl Floyd
Kingsport, TN
(4514 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Electric tach fubar
Posted by: MGBV8
Date: September 22, 2023 09:21AM

When installing new spark plugs, I always put a wrench on them & tighten the top nice & snug with pliers. Never had one loosen up. They sometimes are loose out of the box.

The solid top version of the BPR5ES is part # NGK4006.


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