Mercedes W123 Diesel Fuel Filter Primary Replacement Repair Guide

Difficulty

Very easy

Steps

6

Time Required

                          5 minutes            

Sections

1

• Fuel Filter, Primary
• 6 steps

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Introduction

Be sure to replace this if it looks dirty inside. They are clear for easy inspection. If the filter clogs, it will stop fuel flow to your engine and can leave you stranded. This is one easy item to keep a spare of in your trunk or glove box.

What you need

Step 1

              Fuel Filter, Primary               

• Here is your clear fuel primary filter. It is located directly next to the fuel primer pump.

Here is your clear fuel primary filter. It is located directly next to the fuel primer pump.

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Step 2

• Begin by loosening this hose clamp, at the top of the primary filter, nearest the engine.
• Pull the primary filter up and out of this hose. A small amount of fuel will leak out, consider putting a towel, plastic bag, or other appropriate catch underneath.

Begin by loosening this hose clamp, at the top of the primary filter, nearest the engine.

Pull the primary filter up and out of this hose. A small amount of fuel will leak out, consider putting a towel, plastic bag, or other appropriate catch underneath.

Step 3

• Now loosen the clamp on the bottom of the primary filter, further from the engine.
• You will now be able to pull the filter out the rest of the way. The fuel in it will drain out, catch it with towel or something similar.

Now loosen the clamp on the bottom of the primary filter, further from the engine.

You will now be able to pull the filter out the rest of the way. The fuel in it will drain out, catch it with towel or something similar.

Step 4

• Here is the old primary filter, removed from the car. Note the large chunks of debris in the filter.

Here is the old primary filter, removed from the car. Note the large chunks of debris in the filter.

Step 5

• You can see here the new primary filter. Note that the filter is usually marked with an arrow noting the direction of fuel flow. It should be installed with this arrow pointing towards the engine.

You can see here the new primary filter. Note that the filter is usually marked with an arrow noting the direction of fuel flow. It should be installed with this arrow pointing towards the engine.

Step 6

• Install the new filter by retracing the steps so far, just backwards.
• This is a good time to consider replacing the large secondary filter. If you would like guidance on this, see the secondary fuel filter replacement guide.
• Then, pump the primer pump on the car until the primary filter fills with fuel. It’s normal for there to be a small air bubble in the primary filter but it should be mostly clear.

Install the new filter by retracing the steps so far, just backwards.

This is a good time to consider replacing the large secondary filter. If you would like guidance on this, see the secondary fuel filter replacement guide.

Then, pump the primer pump on the car until the primary filter fills with fuel. It’s normal for there to be a small air bubble in the primary filter but it should be mostly clear.

When finished, run the engine to ensure it’s been primed properly.

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                    Nicolas Siemsen                     

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