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Fuel Gauge, Wow and Thank you #732684
07/02/22 09:07 PM
07/02/22 09:07 PM
Joined: Apr 2021
Posts: 138
San Francisco
R
RobFog Offline OP
L - Learner Plates On
RobFog  Offline OP
L - Learner Plates On
R

Joined: Apr 2021
Posts: 138
San Francisco
Took the Morgan out today, first proper drive ever and wow - it felt amazing, I've been waiting for this moment since I first found the car in the barn back in March last year. I wanted to thank everyone who has given me the advice and confidence to get the car to this far - without your help I wouldn't have known where to start.

Taking it to get fuel for the first time it's clear that the fuel gauge isn't working, it hovers at the 1/4 full mark the whole time and I was wondering if somebody could give some pointers as to the logical steps to isolate the issue or where I should look t get replacement parts.

Thank you all again, I hope I can be a net contributor to the site at some point


1974 4/4 2 seater
Re: Fuel Gauge, Wow and Thank you [Re: RobFog] #732685
07/02/22 09:15 PM
07/02/22 09:15 PM
Joined: Nov 2018
Posts: 4,508
Northants, UK
TBM Online content
Part of the Furniture
TBM  Online Content
Part of the Furniture

Joined: Nov 2018
Posts: 4,508
Northants, UK
Great news!

I'd start with the sender in the tank - take the wire off it. Check you have power coming from it.

Then earth the wire - that should move the gauge needle.

If you have power, and the gauge works, then it's the sender.


1972 4/4 4 seater - 3G Morganeer
Too many ratty motorbikes
Re: Fuel Gauge, Wow and Thank you [Re: RobFog] #732686
07/02/22 09:18 PM
07/02/22 09:18 PM
Joined: Nov 2018
Posts: 4,508
Northants, UK
TBM Online content
Part of the Furniture
TBM  Online Content
Part of the Furniture

Joined: Nov 2018
Posts: 4,508
Northants, UK
You can also check the continuity of the wire from the gauge to the sender, and also check the voltage of the wire going to the sender. It should be around 10V, not 12V. There is a voltage stabilizer that provides the feed to the temp gauge and fuel gauge. Is the temp gauge working OK?


1972 4/4 4 seater - 3G Morganeer
Too many ratty motorbikes
Re: Fuel Gauge, Wow and Thank you [Re: RobFog] #732687
07/02/22 09:54 PM
07/02/22 09:54 PM
Joined: Nov 2018
Posts: 4,508
Northants, UK
TBM Online content
Part of the Furniture
TBM  Online Content
Part of the Furniture

Joined: Nov 2018
Posts: 4,508
Northants, UK
Here's the wiring:

[Linked Image]


1972 4/4 4 seater - 3G Morganeer
Too many ratty motorbikes
Re: Fuel Gauge, Wow and Thank you [Re: RobFog] #732689
07/02/22 10:15 PM
07/02/22 10:15 PM
Joined: Jul 2007
Posts: 22,612
Suffolk
John V6 Offline
Brooklands Register contact
John V6  Offline
Brooklands Register contact
Member of the Inner Circle

Joined: Jul 2007
Posts: 22,612
Suffolk
I would also check the earth. Earths on mogs often fail.


JohnV6
2014 Brooklands Edition Roadster "Brookland's Belle" #5 of 50
Re: Fuel Gauge, Wow and Thank you [Re: RobFog] #732696
07/02/22 11:05 PM
07/02/22 11:05 PM
Joined: May 2010
Posts: 8,462
Llanelli
sospan Offline
Talk Morgan Guru
sospan  Offline
Talk Morgan Guru

Joined: May 2010
Posts: 8,462
Llanelli
I am sure MMC use special metals for the earth.
Probably from the group in the Periodic Table ....Rare Earths.
Apologies but I couldn’t resist ( no pun there either).


Red Plus8
Re: Fuel Gauge, Wow and Thank you [Re: sospan] #732711
08/02/22 09:06 AM
08/02/22 09:06 AM
Joined: Sep 2014
Posts: 2,118
London
MOG 615 Offline
Talk Morgan Expert
MOG 615  Offline
Talk Morgan Expert

Joined: Sep 2014
Posts: 2,118
London
Originally Posted by sospan
I am sure MMC use special metals for the earth.
Probably from the group in the Periodic Table ....Rare Earths.
Apologies but I couldn’t resist ( no pun there either).


Very good!
rofl


Andy G
1999 +8 , Indigo Blue.
Ex-John McKecknie/Mike Duncan 1955 +4 racer.
Re: Fuel Gauge, Wow and Thank you [Re: MOG 615] #732736
08/02/22 02:07 PM
08/02/22 02:07 PM
Joined: Aug 2014
Posts: 1,230
Northern Germany
bmgermany Offline
Has a lot to Say!
bmgermany  Offline
Has a lot to Say!

Joined: Aug 2014
Posts: 1,230
Northern Germany
Originally Posted by MOG 615
Originally Posted by sospan
I am sure MMC use special metals for the earth.
Probably from the group in the Periodic Table ....Rare Earths.
Apologies but I couldn’t resist ( no pun there either).


Very good!
rofl


+1 rofl

Last edited by bmgermany; 08/02/22 02:07 PM.

2005 4/4 1800ccm Duratec and a lot of HONDA CX500.......
Re: Fuel Gauge, Wow and Thank you [Re: RobFog] #732769
08/02/22 09:02 PM
08/02/22 09:02 PM
Joined: Feb 2016
Posts: 5,090
East Harling, Norfolk UK
RichardV6 Online NoMood
Charter Member
RichardV6  Online NoMood
Charter Member

Joined: Feb 2016
Posts: 5,090
East Harling, Norfolk UK
TBM's wiring diagram of the instrument voltage regulator reminds me of the need for same. Late 60's and into 70's and beyond, fuel and temperature gauges worked on the bi-metallic principle where an electrical current would heat such a strip of metal which would distort in a manner proportional to the voltage driving the current, so allowing mechanical linkage of strip to gauge pointer. It also gave very damped readings which was an advantage with fuel sloshing around tank. The technology only worked with a constant reference voltage though, which battery charge systems didn't allow, hence need for 10 volt regulator.

It can be seen if regulation fails an erroneous gauge reading will ensue.


Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1945 Moto Guzzi Airone
Re: Fuel Gauge, Wow and Thank you [Re: RichardV6] #732771
08/02/22 09:18 PM
08/02/22 09:18 PM
Joined: Nov 2018
Posts: 4,508
Northants, UK
TBM Online content
Part of the Furniture
TBM  Online Content
Part of the Furniture

Joined: Nov 2018
Posts: 4,508
Northants, UK
Originally Posted by RichardV6
. The technology only worked with a constant reference voltage though, which battery charge systems didn't allow, hence need for 10 volt regulator.

It can be seen if regulation fails an erroneous gauge reading will ensue.


Yep, replaced mine with a solid state regulator - gives me much more accurate temp and fuel readings. Regulator


1972 4/4 4 seater - 3G Morganeer
Too many ratty motorbikes
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