Author Topic: Testing the Fuel Gauge and Sender  (Read 1651 times)

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JiMoke

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Testing the Fuel Gauge and Sender
« on: March 29, 2010, 07:49:42 PM »
Hi guys,

I did a bit of a search about testing fuel gauges and senders, but only found out about swapping in and out components.

I was hoping someone could tell me how to electrically test each component.  ie, The sender changes resistance?

The gauge can be tested by applying a voltage between xxx and xxx?

Thanks guys,
Nearly there!

Jim

Maddog

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Re: Testing the Fuel Gauge and Sender
« Reply #1 on: March 30, 2010, 12:37:39 PM »
Hi Jim,

First check you have 10V output on the voltage stabiliser. Input is terminal B, 10V out to the gauge is terminal I. It needs to be earthed to work, and should be in the same position as mounted ie. arrow up and unit vertical and horizontal.

The sender should read around 15 ohms when full and 280 when empty (I think - still learning to drive a new multimeter ;)). All my moke ones are keeping the petrol in the tank, so I checked a new mini one that I am going to convert. Same gauge, so should be the same.

The gauge doesn't seem to have any markings on it, but on mine the 10V input is on the left looking at the back and the right terminal is the sender wire. It should read full when you earth the sender - but the book does say not to do that for some reason.

If you have everything out you could hook it all up and test it. I've got a diagram here if you need it - but it's pretty straight forward.

Hope this helps.


Cheers, MD.
Mickey 81 Californian Arnold 82 Californian Baldy 82 Californian Ron 79 Califakian Eskymoke 82 Californian

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JiMoke

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Re: Testing the Fuel Gauge and Sender
« Reply #2 on: March 30, 2010, 10:53:09 PM »
Thanks MD,

Those numbers are a great help!

However......

I have tested the gauge and it works beautifully (earthed it for a while as the needle creeps up), the sender measures about 200ohms (when the connection is removed from the back of the gauge and tested against a ground.  But... when connected I don't see anything on the gauge!  I have roughly half a tank of old dinosaurs, so I'm not sure what the problem is.

I do have a relatively narrow gauge of wire from the tank to the gauge, so might try a bigger one tomorrow, but I can't imagine the gauge draws much current.

Cheers,
Jim

JiMoke

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Re: Testing the Fuel Gauge and Sender
« Reply #3 on: March 30, 2010, 11:05:26 PM »
Nope,

Not a wire gauge problem.  Just ran out to the shed and connected a nice fat wire in and no go....is it possible my float is jammed in the empty position?  Can the float be actuated in car or do I need to drop the tank and pull the sender out?  (Will be a pain, cause half a tank of premium dinosaurs weighs a bit!)

Night all!

Cheers,
Jim

Maddog

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Re: Testing the Fuel Gauge and Sender
« Reply #4 on: March 31, 2010, 12:34:52 AM »
Jim,

More than likely the float has a hole in it. It is now probably full of dinosaur DNA and resting peacefully at the bottom of the tank.


MD.
Mickey 81 Californian Arnold 82 Californian Baldy 82 Californian Ron 79 Califakian Eskymoke 82 Californian

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JiMoke

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Re: Testing the Fuel Gauge and Sender
« Reply #5 on: March 31, 2010, 10:05:52 AM »
You might be right MD,

Looks like I'm going to have to work out a bit and build up my scrawny muscles for the tank removal.

Cheers,
Jim

77Devil

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Re: Testing the Fuel Gauge and Sender
« Reply #6 on: March 31, 2010, 11:40:40 AM »
Hey Jim,

I found mine was quite light, when I had taken the fuel out first!

Cheers

Dev
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martin

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Re: Testing the Fuel Gauge and Sender
« Reply #7 on: March 31, 2010, 03:00:40 PM »
Quote
More than likely the float has a hole in it. It is now probably full of dinosaur DNA and resting peacefully at the bottom of the tank.

I have that problem - is the float the same as mini?
Martin
Retired Stormtrooper

mouse_zzr600

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Re: Testing the Fuel Gauge and Sender
« Reply #8 on: April 01, 2010, 07:41:20 AM »
Hi Guys,
You will probly find float is fine ( however it may have fallen off the sender )
The sender unit itself is nothing more than a simple variable resister.
Its readigs have no real values. ( in car ) to test disconect wire from sender and connect +ve wire from multimeter to sender unit and -ve wire to earth, turn on meter set to ohms ( high end of scale )and it should show an ohmege reading. Depending on which tank u have ( top fill easiest ) lift float and watch meter the reading should increase. if it doesnt the sender is issue. if it goes to infinity , overload or jumps around iratically it has a break in wire so rebuild is needed.
The unit works by a bimetal strip working the wires and most times it is these wires ( internal to the sender ) or the bimetal strip that are broken or worn.
With a  bit of time and patiance these can be replaced ( rewind with the suitable wire and a dob of solder on the strip )
If you go the rewire way it needs to be non insulated or it wont work. This process took about 1 hour to perform with the right tools, wire and solder etc.
New units:- I replaced mine with new aftermarket and it lasted about 2 months so i rebuilt my orig and it has been working fine for the last year + or so
Hope this helps
Regs Mouse ( aka Slomat )

JiMoke

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Re: Testing the Fuel Gauge and Sender
« Reply #9 on: April 01, 2010, 08:33:16 AM »
Hi Mouse,

I have a top fill tank, but unfortunately, can't see the float due to a baffle being in the way.

Looks like it has to come out!

Cheers,
Jim

moke123

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Re: Testing the Fuel Gauge and Sender
« Reply #10 on: June 12, 2020, 02:24:46 PM »
I came across this guide by Moss Motors for troubleshooting voltage regulators and fuel senders today.  Haven't had to use it, but it seems quite good.

https://mossmotors.com/media/instructions/131-555.pdf

Terry

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Re: Testing the Fuel Gauge and Sender
« Reply #11 on: June 12, 2020, 04:36:37 PM »
Hi,

thanks for sharing. It is interesting that they also made and supply a solid state replacement.

Terry
I'm not questioning your powers of observation; I'm merely remarking upon the paradox of asking a masked man who he is.


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Steam

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Re: Testing the Fuel Gauge and Sender
« Reply #12 on: June 12, 2020, 05:41:41 PM »
The float is plstic and clips into the wire of the sender then it may be full of fuel.
Ironically there will not be a hole in the float and if you leave it in a warm place for a few weeks the fuel will evaporate out again. It will fill up again but takes a few years.
The 10v is adjustable on the old ones, I have converted plenty to solid state. PM me if you want one.
You should also be able to hook the float lever with a wire, coathanger, fencing etc  ent to a hook e d, and lift to simulate a full tank.
Cheers, Dave

 

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