Author Topic: Fuel Gauge Connected Directly To Sender  (Read 19844 times)

BobH

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Re: Fuel Gauge Connected Directly To Sender
« Reply #75 on: July 31, 2023, 09:08:38 »
So reading all this new information that popped up I saw someone state that the Gage when full when unplugged from the Fuel Sender.  So I tried that, and it stayed empty...

Hello, don't get hung up on the above statement, it's not correct, with the sender connector plug unplugged the gauge will remain on empty, as there is no ground feed to it

i guess what you should try before anything else, is simply to tap the cluster glass with your finger, the needle can get stuck when the gauge hasn't moved for a while, my gauge needed a nudge for months until it eventually freed up through regular use

The next thing to try is to make sure you have a good ground at the sender unit, the brown wire on the connector, your readings in your last post may indicate that the ground is ok, but may not.  I suspect your meter may not have been used correctly, apologies if it sounds like i'm teaching you how to suck eggs

All tests should be carried out with the ignition off

With the meter set to ohms (omega sign) and the meter leads plugged into common and the terminal to the right, ohms, AmAv (terminal A to the left of common is not used for continuity tests).  Set the meter to 200ohms.  When the leads are shorted together, you should read 00.0

If that's ok, put one lead on a good ground, next to the rear lights is easiest, the other end of the lead on the brown wire on the connector, again should read 00.0.  If you read OL then run a temporary wire from the ground to the brown wire terminal on the connector and then try the gauge with the ignition on
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acbrock

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Re: Fuel Gauge Connected Directly To Sender
« Reply #76 on: July 31, 2023, 18:57:55 »
Bob, so I rechecked with the Meter.  Meter goes to 0.00 when I touch the leads and when I did the Ground from the Plug to the Ground at the rear light it goes to 0.00 too.   So assuming good ground.  I tapped the gage with no result.  Is there easy way to get at that gage or is it taking the whole dash apart.  I will start looking into that.  Everything works on the dash but the Odometer so I need to have that rebuilt or cleared up.

ps... no worries on sounding like you are teaching me!  I am here to learn!  Pretend I am 5 years old!  I guess I am not even 5 considering the years and experience I have working on cars!
« Last Edit: July 31, 2023, 19:34:32 by acbrock »
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rwmastel

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Re: Fuel Gauge Connected Directly To Sender
« Reply #77 on: July 31, 2023, 19:31:54 »
Is there easy way to get at that gage or is it taking the whole dash apart.  I will start looking into that.
Getting the gages out is a bit of a pain, from what everyone says.  I've avoided it so far, but may be doing it this fall. 

Did you get the sender out of the tank yet?  Maybe the float is stuck.  If you do pull it out, buy a new seal for putting it back together.
Rodd

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BobH

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Re: Fuel Gauge Connected Directly To Sender
« Reply #78 on: July 31, 2023, 19:35:11 »
Before you start taking the gauge out, which entails taking the instrument cluster out, which is quite a task, you could just try eliminating the sender as the problem, by bridging the earth pin on the plug to the other two pins, ground to the blue black wire should activate the gauge, and ground to blue green wire should illuminate the low fuel light, do these tests with the ignition on

If both of those work, then the problem would seem to be with the sender, which could be damaged or could just need a clean, there's tips on how to pull the sender out on one of the earlier threads.  I'm not sure what condition your fuel and tank is in if it's been standing for years, i guess the tank may need emptying and flushing, if you search, again you'll get some advice

If linking across the pins still doesn't work, then you'll need to look at the actual wiring between the sender and the gauge, which goes via a 12 way connector under the dash, there's a picture of the pin arrangement in the tech manual, button above left, and then use the search function when you're on the tech manual home page.  You can visually inspect the connections at both ends, as the wiring can deteriorate over time, particularly where they are soldered onto the connector pins

You could also make sure fuse 5 is ok, i think that also serves the reversing lights and brake lights, so perhaps check if both of those are still working.  Sometimes the fuses need twisting in their holders, as they can build up resistance over time
« Last Edit: July 31, 2023, 19:59:31 by BobH »
February 1965 230SL Automatic
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acbrock

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Re: Fuel Gauge Connected Directly To Sender
« Reply #79 on: July 31, 2023, 20:28:10 »
Awesome!  Thanks BOB!  That was the little trick I needed.   So when connecting wires, Reserve light went on and also Tank when full.   So I guess today I get that fuel sending out and hopefully just give it a good cleaning!
Thanks!
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acbrock

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Re: Fuel Gauge Connected Directly To Sender
« Reply #80 on: July 31, 2023, 21:30:38 »
Always something.  So I got the sender out.  Figured I should take it apart and clean it.   Bottom metal piece came off I cannot get the plastic piece beneath it off. I feel like I am going to destroy it.  From the picture on the link below it looks like the plastic piece is just placed on there... Think I could just push the protruding screwpin from the bottom to pop the top of the sender off?  Or will I wreck the inside.  I might just put it back in now that I took it out and can hear everything floating around inside.  Maybe it just needed to be moved and drained?  Or think should soak it in water/venegar if I cannot get it open?

https://w113-eu.translate.goog/geschlossen/Reparaturen/Geber%20fuer%20Kraftstoffanzeige%20Pagode%20W113.htm?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp

Also just went out and attached the Sender to the car and turned it on and tilted it upside down and right side up.  Same problem I have had the whole time.  Nothing on the gage just a little jump.  So I am guess something is broken inside this sender?

After thinking about it... I guess if the Sender is bad then I should not worry too much about busting it open.  Kind of want to do it just to confirm it is broken inside... I searched and Mercedes has a parts shop near me and they have a new Fuel Sender I can pickup tomorrow for $200.  I might do that tomorrow or the next day.  Much cheaper than taking to the mechanic....
« Last Edit: August 01, 2023, 05:33:00 by acbrock »
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rwmastel

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Re: Fuel Gauge Connected Directly To Sender
« Reply #81 on: August 01, 2023, 06:24:21 »
I think people have tried to clean these before, but maybe just chemically and not through disassembly?  This would have been a very good topic to search on, before taking it apart.  Some people like to make existing parts work, some like to replace everything with new.  Hopefully it can be salvaged.

You may need a professional fuel tank cleaning & sealing if it is rusty inside.  Some members attempt it themselves.

Replace the inexpensive fuel screen that is screwed into the bottom of the tank.

Replace the main fuel filter in the engine bay.

And which car (year) do you have?  It would be a good idea to put that in a signature so people can provide accurate help based on your car specifics.
Rodd

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BobH

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Re: Fuel Gauge Connected Directly To Sender
« Reply #82 on: August 01, 2023, 07:39:37 »
Have a search to find the best method of cleaning, you may be able to salvage it

You should always disconnect the battery when removing the sender, don't want any sparks when the tank is open and there are fumes in the trunk and car

Did you find out how to start a new post?  If you search the help pages, above left it will give you advice on how to navigate around the site

Good luck!
February 1965 230SL Automatic
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Pawel66

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Re: Fuel Gauge Connected Directly To Sender
« Reply #83 on: August 01, 2023, 09:11:13 »
If I may add, as I went through pulling out the sender:
- avoid doing that with completely full tank; with a full tank a small pressure on trunk floor may result in huge spillage of fuel through the hole where sender was
- get equipped with a new seal for sender before you start disassembly; best from Mercedes in my opinion
- be careful not to break off the studs from fuel tank; maybe apply some penetrant in advance on the nuts
- it is work with fuel - have something at hand (fire extinguisher, blanket) to put out fire
- avoid 220V portable garage lights
- as advised, disconnect battery
Pawel

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acbrock

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Re: Fuel Gauge Connected Directly To Sender
« Reply #84 on: August 01, 2023, 16:23:11 »
Hey Gang thanks for all the input....

RW… I wills search the chemical cleaning now.  I never got it apart for fear of breaking it!  I am someone who will 100% always want to repair not replace.  I will check on the tank.  About a month ago when I decided to get it running again and start to restore, I took it into a shop that I had taken it in the past.   Actually the shop that has been servicing the car since 1971.  Unfortunately the shop changed hands about 3 years ago.  But one of the mechanics stayed on and he worked on the car.  So he went thru the car and drained the tank and replaced a bunch stuff so that I could feel the car was mechanically safe for me to drive.  So I will double check on what they found in the tank.  They were very impressed that the car had no rust, so I assume the tank should be ok.

BobH… Just so you dont think I am crazy.  Yes I had the battery off during all of this.  I only plugged it back in when I did the test on the Sender.  I covered the tank up and I am working outside.  But always feel free to send safety stuff, I know there are tons of little things that I might not realize are completely dangerous.  If I had not read about taking the battery off when working on the sender before I started I probably would not have thought it was necessary!

No still cannot post a new topic!  Can you send me a picture of the buttons you have?  Maybe I am starting right at it but in the help notes it says there should be a Post New at the top and Bottom and I dont have either?

Paw… Blew that, did not realize I had a full tank because I had no gage!  Or not full but full enough to make a mess!  I think I will go to Mercedes today and get the Sender and seal while trying to clean out the old one.  I got it off without hurting the studs!  Buying another fire extinguisher today!
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rwmastel

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Re: Fuel Gauge Connected Directly To Sender
« Reply #85 on: August 01, 2023, 17:05:11 »
No still cannot post a new topic!  Can you send me a picture of the buttons you have?  Maybe I am starting right at it but in the help notes it says there should be a Post New at the top and Bottom and I dont have either?
Rodd

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acbrock

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Re: Fuel Gauge Connected Directly To Sender
« Reply #86 on: August 01, 2023, 17:24:37 »
Yep it is there!  I guess it is just not on all the pages.  I only have it on the page when I back up to Electrical an Instruments.  It is not on this or the main Page.  So I guess I just need to find the correct group in the forum and post there.  Makes sense!  Knew it was something stupid and simple.
Thanks!
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rwmastel

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Re: Fuel Gauge Connected Directly To Sender
« Reply #87 on: August 01, 2023, 17:30:32 »
Well, you can't start a new topic from within a current topic, only from within the forum, if that makes sense?  So, if there is a list of topics displayed, then you can start an additional topic there.  Once you start discussing a few different topics and using the different sections of the forums, then it will all become second nature.

Getting used to the Search function is the most important thing!  Sooooo much information available.  You'll be a Pagoda Expert by Thanksgiving.   :D
Rodd

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1966 230SL auto "Italian"

acbrock

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Re: Fuel Gauge Connected Directly To Sender
« Reply #88 on: August 02, 2023, 00:20:13 »
Ok now I can create new post!  I posted something earlier and added pictures but it is not here so maybe I dont have picture ability yet.   But went down to Mercedes Benz today in Long Beach what an insane facility.  They were working on a bunch of cars for the Pebble Beach show next month! Wow. So I bought a new Sender in case the cleaning Rehab on mine failed...

Search forum for Cleaning and sent a message to a guy who had done it a bunch of times.  Got my sender open to clean tons of crud came falling out.  I will attach a pic!  Then once I got the send out, 1 of the wires was not connected out of the 3.  And it was a mess.  I sent the pics off to the guy and he said it was the worst one he has seen and he would not tackle it.  So I did a quick clean and boxed it up to attack later in life when I get better at this.  Dropped in the New Sender and Boom!  Everything fired up and gage works perfectly!  So I think my probably (first of many) is solved so I won't post here anymore.  I will start new threads!  But I am sure I will track you all down with questions. 
So thanks for everything!
I am going to post his and see if it posts, then post the pictures in a separate post to see if they post...
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acbrock

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Re: Fuel Gauge Connected Directly To Sender
« Reply #89 on: August 02, 2023, 00:28:10 »
Pics...
1966 230SL Automatic 717G Papyrus White "Minny"