How to repair a MB/GPW fuel gauge. Lots of pics

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
Steve Bump
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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by Steve Bump » Thu Dec 31, 2009 8:18 am

Correction: Unit does function now, probably the result of cleaning up the posts and improving connectivity. Battery test did help to know the unit itself was not at fault, so may be a useful tool. Certainly this sticky has been invaluable to many of us. Thanks, Elwood, Sean, and others!

Steve

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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by mahughes » Thu Apr 22, 2010 2:01 am

Hello Elwood -

I'm a first time forum user, so please be gentle with me.

I am trying to get my fuel gauge to work and your sticky is very informative.

My gauge us showing the exact same sytmptoms as Marcel Brands but unfortunately I cannot find your reply to his questions.

What am I doing wrong?

Any help would be greatly appreciated.

Cheers
Mark
1944 Willys MB #336328 "Charlotte"

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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by jag » Tue Jun 08, 2010 4:03 am

Thanks for an interesting post. I have a related question. My jeep has a NOS Stewart Warner fuel gauge. I have just installed a repro tank sender unit and the gauge works well. Only issue now - there is what appears to be an oily type smear appearing on the inside of the gauge glass. I assume this must be some of the original lubricant leaching out now the gauge is working. I would appreciate any further advice on what this could be and how to remidy without damaging the gauge. thanks

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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by Chuck Lutz » Tue Jun 15, 2010 12:15 pm

That might be condensation forming inside the glass face.
Chuck Lutz

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kjm
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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by kjm » Sat Jun 19, 2010 7:31 pm

Hello,
Can you tell me what to do if my fuel gauge moves around when I'm driving?
Thank you, Kjm


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jeepmb
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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by jeepmb » Sat Sep 11, 2010 6:21 am

Hello ElwoodJBlues,

Thanks so much for your sticky note!!!

Best Regards,

Luigi

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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by Benleroy » Thu Nov 18, 2010 4:25 am

kjm wrote:Hello,
Can you tell me what to do if my fuel gauge moves around when I'm driving?
Thank you, Kjm
Dont drire :mrgreen: :mrgreen:

It's a problem of mass.

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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by ng19delta » Thu Nov 18, 2010 5:21 pm

kjm wrote:Hello,
Can you tell me what to do if my fuel gauge moves around when I'm driving?
Thank you, Kjm
Stop until the needle settles, and attempt to drive again. Should it resume swinging, ignore it till the funny sound under the hood stops, and the fill up with gas.

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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by Donovan » Mon Jan 24, 2011 7:31 pm

Need some help.

I have a 12V gauge and sending unit. All I get is a full reading. I checked the sending unit and I do get a range of resistance from low to high setting (sorry, I do not remember the values). The gauge is rebuilt by Sean Elliot and I am assuming works correctly. In reading the posts, everyone is checking the gauge post to ground value. Does this matter? Does the gauge need to be grounded to work properly? I know the sending unit needs to have proper ground but why the gauge? Isn't the gauge a simple resistance meter?

Any help would be appreciated.

So close with my restoration but so far!

Donovan.
GPA 11374

Marty, SoCal
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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by Marty, SoCal » Tue Jan 25, 2011 1:34 pm

The original guage grounds through the case to the dash, it's important that it has a good connection or the reading will be incorrect. Some aftermarket guages have a third stud for the ground which makes getting a good ground easy.
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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by Eddie Holland » Fri Mar 04, 2011 8:24 am

does anyone know if there is a source for replacment benzels and gauge faces or even stickers to replace the gauge faces?
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kjm
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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by kjm » Wed Aug 31, 2011 1:02 pm

Hello,
Nice job on the gauge, Can you tell me what would make the needle jump or move when driving?
Thanks

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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by ElwoodJayBlues » Fri Sep 02, 2011 5:21 am

The needle on these gauges will always be jumping and moving.
It will even move when you rock the jeep by hand.

They're not compairable to modern fuel gauges.

So if the gauge works when the jeep stands absolutely still, you're fine!

EJB
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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by kjm » Fri Sep 02, 2011 12:12 pm

OK, Thank you,
Kip

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Re: How to repair a MB/GPW fuel gauge. Lots of pics

Post by YLG80 » Fri Nov 25, 2011 5:07 am

Thanks to ElwoodJayBlues for sharing his method to repair a fuel gauge
I have successfully repaired my original gauge thanks to him.
A coil wire was cut on the IGN post. :wink:

As I had the complete fuel gauge installation on my electronic workbench (fuel sender wired to the gauge and a lab power supply (6V) ),
I’ve fully tested the assembly and slightly adjusted the gauge needle deviation.

With the gauge type repaired using ElwoodJayBlues method, it is possible to adjust the needle full deviation by bending a soft iron blade. (see picture)
gauge_adjust2.jpg
gauge_adjust2.jpg (15.84 KiB) Viewed 3268 times
If you bend the blade, sticking it to the coil, you will increase the iron loss in the magnetic circuit wich will in turn reduce the needle deviation.
You have to carefully adjust that blade so that the needle will still move back to the zero (empty tank) stop.

This is sometimes usefull, as the needle hits the FULL tank stop violently when you switch the starter switch ON with a tank full of gas.
I could see the shock traces on the needle in my gauge.

Depending upon the fuel sender resistor, my gauge needle was not fully returning to the zero stop with an empty tank.
This can also be adjusted.

In fact the instrument behaves as an ammeter connected within a measurement bridge.
If you connect a parallel resistor of a low value between the two posts, you will reduce the instrument sensitivity.
With my gauge, I connected a 39 ohm resistor between the two posts, so that the needle deviation was OK and soft between the EMPTY stop and the FULL stop.
Depending on you sender resistor value from min to max, you would have to use another resistor value close to 39 ohm.

The next picture shows you how to connect the resistor.
IMG_0975-notes-web.JPG
IMG_0975-notes-web.JPG (105.12 KiB) Viewed 3268 times
It’s better to connect the resistor externally, so that if you change your fuel sender you can remove or change the resistor value.

For those questioning themselves on why the needle is jumping and moving all the time, this is normal.
In that type of gauge, there is no spiral spring around the needle to absorb the shocks or vibrations.
The needle is driven by the magnetic field balance between two coils.
This a fragile balance easily broken by the needle weight and inertia.

Yves
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