Fuel tank sender

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gooch
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Hi guys, recently on my 2001 G400 my fuel gauge does not go over the first quarter on full tank?

I have checked the sender unit- no gunk very little corrosion which i try to clean as much as i could.

There seems to be no more than. 1 volt coming from the wires.

Should there be a full 12volts on ghe Plus wire?

Has anyone had or know where else i can look for the problem?

 

Thanks gooch

 

JASONGDS
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Re: Fuel tank sender

Did you remove the alloy cover of the sender ? The float can get trapped by diesel gunk

 

gooch
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Re: Fuel tank sender

JASONGDS wrote:

Did you remove the alloy cover of the sender ? The float can get trapped by diesel gunk

 

Hi thanks for getting back to me! Yes the round cylinder thing i removed. I cleaned all the contacts inside them not a lot of gunk at all. Going to try the fuel pump relay next, maybe theres a bad curcuit in it possibly hence why theres no voltage at the wires ontop of the sender unit. 

Will keep you posted

 

JASONGDS
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Re: Fuel tank sender

Only familiar with my early 463, but on that if you earth the feed the gauge will read full?

JASONGDS
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Re: Fuel tank sender

When you say cylinder removed, you did mean you took tube off exposing the float?

gooch
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Re: Fuel tank sender

Hi mate,

Yes the metal looking cylinder, i will try direct earth connection tomorow 

gooch
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Re: Fuel tank sender

JASONGDS wrote:

When you say cylinder removed, you did mean you took tube off exposing the float?

 

So today i did x3 other things to remedy

1. Watched a video on a STAR bulletin to mercedes garages Confirms how to reset fuel gauge ! Interesting stuff so basically the fuse relating to Instrument cluster theres x2 of them in my 2001 you simply take them out with iginition off then re-insert fuses and turn on ignition see if that works..... this remedy apprantky resets the fuel gauge and reads new tank reading from sender unit.! - nothing happened

 

2. Then i checked the ground and connected fresh wire to body- again nothing happened

 

3.  Whilst key in ignition position 2. Then i noticed very small pulses on the + plus lead ontop of sender unit whilst checking live in wire....i then connected a fresh 12v to the sender unit and i then  heard a click noise what sounded like the speedometer and yes the gauge read 3/4 for the first time - i did this whislt the key was in position 2. I think somehow these speedo clusters have some kind of memory in them- its also used on W203 c-class models.

So it seems good now possibly had low voltage mis information from speedo to sender unit, it must have reset itself whilst giving sender unit fresh postive feed.

Hooray!