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

Post by ElwoodJayBlues » Wed May 21, 2008 1:49 pm

Hi

During the last days I fixed a bunch of original fuel gauges.

I thought I´d put a "How-to / step-by-step" together, so everybody here on the Gee can see that there´s no magic involved...

It can be done with simple tools and allthough it won´t reach the grade of a professional restoration (like Sean´s work), it will work.

First step:

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A dirty, well used, original 6 Volt two connector fuel gauge, the WWII jeep standard model.

First measurements:

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The resistance between the two posts is about 36 Ohm here. That´s ok. I measured values between 30 to 42 Ohms here.

next step:

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Uh-oh :shock:

here´s the problem of 99% of all fuel gauges.

The resistance between the left connector and the housing is infinite here. That´s wrong!!

Ok, so we´re going to dismantle it:

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I´m using a special tool, but a big screwdriver will work, too.
Here´s a closeup of my tool:

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When you bent the lid a bit, a small pair of pliers will do the rest:

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After going round the lid with the pliers, you can remove the lid. Then you´ll have this here:

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Some parts and a lot of dust and dirt...

To get the mechanics out of the housing, you´ll have to remove the two nuts from the connectors.
I put them in my bench vice with a rag to protect the thread...
Then I remove the nuts with some pliers...

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Then you can completely dismantle the gauge:

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Make sure not to loose the two insulator washers!

And here we see our problem:

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There should be contact between the rear wall of the housing and the brass plate in the middle of the rear...

Here is the gauge itself, after removing the dial, front view:

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And here again, with instructions, what goes where:

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But first we´re going to measure the resistances of the two coils:

Coil one:

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It is the coil that is connected to the housing and the left connector (=the right one on this front view!) It should have a value between 40 to 55 Ohms.


Coil two:

Image

It is the one that is soldered to the two connectors.

It should have a value between 30 and 32 Ohms, the same we´ve measured before.

Here´s again what has to be soldered where:

Image

Coil one (the left one in the pic) has it´s rear wire soldered to the connector in the middle, on the rear brass sheet.
The front wire is soldered to the right connector, together with the right front wire of coil two.

Coil two (the right one in the pic) has it´s left wire soldered to the left connector.

Additionally, I solder the threaded bolt and the loop of the connectors together to secure a good and durable contact:

Image

After that, you can secure the threaded bolts with some two component resin or something similar...

Next thing to do is to solder the rivet and the rear brass sheet together for the same reason:

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Here´s a pic of the ready soldered gauge, showing the wires connected to the right spots:

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Now we can take the measurements again:

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Good value!

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Good value, too!

What comes next is additional work. It is not original, but I think it can´t be seen and secures a durable function of the gauge.
It´s up to you if you want to do this:

Solder a piece of wire to the brass plate on the rear:

Image

The other end of the wire is soldered to the inner side of the housing itself:

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If you don´t want to add this wire, you just have to clean the rear inner wall of the housing with a file and the rear brass sheet to secure good contact.

Next step:

the dial goes back on:

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Be sure to bend the hand straight, so that it won´t touch the dial or the front glass!

Put the two small insulator washers back on and stick the complete gauge back into the housing.

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Be sure not to turn it upside down! The notch of the housing must be at the 6 o´clock position.

Secure the gauge with two new lockwashers and nuts.

Now is the time to measure again:

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Value between the two posts is still ok.

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And -- TADAAA! --- the value between left post and housing is fine, too. Now the fuel gauge should work just fine for a looooooong time!



All you have to do now is clean dial and glass and lid, and put everything back on.
The rim of the lid gets bent over with a pair of pliers. Then just paint it.

Last thing to do is claen the back of the housing´s outside to secure good grounding to the dashboard and the dashboar clamp.


You see, it´s not hard to make a fuel gauge work again!

My advice here is just for the WWII 6 volt modell, I don´t know if it works for the later types, too.
The grounding problems are the same. The Ohm values should be different, though.

If you have any questions or improvements, please let me know!

Moderators, if you think this is ok, you could make it a sticky.

Hope this helps!

Cheers from Germany,

EJB
MB 134202, stamped grill, script back
"Lili Marlene"

"Vor der Kaserne, vor dem großen Tor..."

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Post by Bangle 99 » Wed May 21, 2008 1:59 pm

Very nice. Moderator, this should be made into a Sticky.
Jim
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Post by lucakiki » Thu May 22, 2008 1:16 pm

INTERESTING!
Luca

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Way too many WWII military tools,hopefully thinning down,and way too many posts...

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Post by Swiebertje » Fri May 23, 2008 5:21 am

CHEERS, very help full.

Wil
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Post by Robert Tofson » Fri May 23, 2008 12:06 pm

Thanks ElwoodJBlues.......... :D You're a very talented Jeep guy. Great sticky, good info.
"FireBall"
I have a 1945 MB, DOD 16 Jan 1945, MB # 407049, Hood # 20673717 S, Engine # MB 537670, Body Serial # 178043
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Post by fredjc1 » Sat Jun 14, 2008 7:02 am

EJB,
Thanks to your excellent sticky I now have a fully working original gas gauge :lol:
The info was so clear and easy to follow, it took the fear out of what I thought was an impossible job.

Good job, thanks for taking the time to share your knowledge.

Cheers
Fred :D

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Post by R.P.Witt » Thu Jun 26, 2008 2:31 am

Hi,
my jeep is converted to 12V electrical system. The fuel gauge does not work. I dont know if is the problem of gauge or the gauge dont work with the 12V electrical system. :( :?:

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ElwoodJayBlues
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Post by ElwoodJayBlues » Thu Jun 26, 2008 3:17 am

An original 6 Volt gauge will not work in an 12 Volt system. Same goes for the sending unit.

But you can get repro gauges and sending units that are made for 12 Volt...
MB 134202, stamped grill, script back
"Lili Marlene"

"Vor der Kaserne, vor dem großen Tor..."

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Fuel gage

Post by Marcel Brands » Mon Jun 30, 2008 6:44 am

Hi Elwood,

Great performance on this antique gage! Very educating! Do you mind me asking a question about my gage problem?

I put a new 6v fuel sender in my tank (tank is half full).
Then I try to find out whether my gage is working.
According to your gage story I measured 26 ohm between the two posts.
Resistance between "F" (side of full sign) post and housing is 28 ohm.
Resistance between "E" (side of empty sign) post and housing is 54 ohm.
Do I have a correct working gage?
My gage has a label attached to the "F" post that says "connect sender wire to this post" ("if hot wire touches, sender will be damaged"). The posts are totally insulated from the housing and the bracket.
Now I attach fuel sender to "F" post (according to the label), I hold the gage on a ground spot and put a wire hooked up to the battery (with a 5 amp circuit breaker in it) to the other post. Now the indicator in the gage flips fast and firm from "E" to "F" where it hits the other side. This is definetly not right! Same thing happens if I change posts.
What do I do wrong and in which way should I systematically work to find out the problem?
Thank you very much if you can guide me through this small puzzle!
Would be wonderfull to learn from you!

With regards,
Marcel Brands
ASTRO705

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ElwoodJayBlues
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Post by ElwoodJayBlues » Fri Jul 04, 2008 12:19 am

There´s one problem for me...

The label says: "Connect sender wire to this post". And this label is on the right hand post? I mean the right post, when you´re looking at the face of the gauge and the left hand post when you look at the backside of the gauge??

That´s wrong...

Could you post a pic of your fuel gauge, please?

EJB
MB 134202, stamped grill, script back
"Lili Marlene"

"Vor der Kaserne, vor dem großen Tor..."

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Fuel Gauge

Post by hell-fire » Sun Jul 06, 2008 2:09 am

EJB,

Thanks for this very informative Post,

I will make use of your information. :shock:
John
Australia
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1942 Willys MB-BRT 135673 D.O.D. 4-16-42 Now 97% finished
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Post by 30Caliber » Thu Jul 31, 2008 5:53 pm

Outstanding! I can now rebuild all of mine. Thank you.
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Post by johnny43gpw » Tue Aug 19, 2008 5:36 pm

Very well done !! Post more stuff like this, We love it !!!! :D
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Post by autocar » Sun Aug 24, 2008 8:06 am

Very nice!!! Thanks for info.

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Post by timjames » Thu Mar 19, 2009 1:42 pm

Will try tommorow. have 3 of them rusting
Tim

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