Mercedes W123 Fuel Sending Unit Replacement Repair Guide

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Easy

Steps

Time Required

                          5 minutes

Sections

Fuel Sending Unit
4 steps

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Introduction

What you need

Step 1

              Fuel Sending Unit

Before being able to proceed you will need to remove the first aid box. This guide does not cover this step, but basically, when you remove the first aid kit you will see several Phillips screws in the bottom of the box. Remove those and the first aid box lifts out.

Before being able to proceed you will need to remove the first aid box. This guide does not cover this step, but basically, when you remove the first aid kit you will see several Phillips screws in the bottom of the box. Remove those and the first aid box lifts out.

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Step 2

With the box out, you will see the top of the sending unit where it screws in to the fuel tank.
On top of the sending unit is a large black plastic plug for the wiring that goes to the fuel gauge. Start by removing this (not pictured) by pulling straight up on it.

With the box out, you will see the top of the sending unit where it screws in to the fuel tank.

On top of the sending unit is a large black plastic plug for the wiring that goes to the fuel gauge. Start by removing this (not pictured) by pulling straight up on it.

Step 3

Use your large socket (1 and 13/16") and a ratchet to unscrew the fuel sending unit.
Optionally, you can use a large adjustable wrench or channel locks though when using tools like this there is always the potential for damaging the top of the fuel sending unit. Having the correct size socket is always preferable.

Use your large socket (1 and 13/16") and a ratchet to unscrew the fuel sending unit.

Optionally, you can use a large adjustable wrench or channel locks though when using tools like this there is always the potential for damaging the top of the fuel sending unit. Having the correct size socket is always preferable.

Step 4

You can now begin to pull the fuel sending unit out. Do it slowly.
Before removing it all the way, let the fuel in the unit drain out. You should hear it slowly draining as you pull it up. The more fuel that is in your tank the longer it will take to drain the unit.
Once it’s drained you can remove it all the way to service it or to proceed at installing your replacement part.

You can now begin to pull the fuel sending unit out. Do it slowly.

Before removing it all the way, let the fuel in the unit drain out. You should hear it slowly draining as you pull it up. The more fuel that is in your tank the longer it will take to drain the unit.

Once it’s drained you can remove it all the way to service it or to proceed at installing your replacement part.

To reassemble your device, follow these instructions in reverse order.

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                    Nicolas Siemsen

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Chris Yeyna - Oct 21, 2016

while soundproofing my 84 300d i removed the box and covered the hole with sheet metal. thanks to you i will be removing the metal and trying to remember if i kept the box. the lid was already missing. good stuff thanks p.s. i think i will weld a 1/2" drive socket onto my 1 13/16" socket. i have extras

vwnate1 - Nov 2, 2016

11.2.16

For Diesel cars, the sender often has fungus lurking inside it and it’s easy to take apart and clean if VERYDELICATE* .

Use some small delicate pliers to pinch the soft plastic surround protecting the special nut and unscrew it then it all comes apart easily .

Work over a clean light colored cloth and use electro - contact cleaner or aerosol starting fluid to clean the funky black fungus ~ you need to get every bit of it out, use a soft toothbrush on the bottom part .

Test easily by tipping the sender up and down with the plug attached and the key on .

-Nate

Craig - Mar 11, 2022

My car has been sitting for 9 years and they’re sending unit isn’t working or the gas gauge does not work. What should I check for first.

Edgar F Arabia - May 29, 2018

God pm sir.how much is fuel sending unit for 123/300d

Hugo Uribe - Aug 25, 2018

Sable Quisiera donde lleva el tiempo de temperatura mercedes ben 280e 1981

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Introduction

What you need

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