How to purge your Mercedes W123 diesel

Introduzione

Diesel fuel tends to be a bit "dirty" compared to gasoline. Keep your fuel system running in tip top shape by occasionally running some diesel purge through it.

The ideal time to do this is just before you plan to change both of your fuel filters as they should always be replaced after a purge.

Cosa ti serve

Passo 1 How to purge your Mercedes W123 diesel

How to purge your Mercedes W123 diesel, How to purge your Mercedes W123 diesel: passo 1, immagine 1 di 1

To begin, loosen the clamp on the rubber fuel hose that connects to the supply hard line. The supply line is the lower of the two, where the hose goes to the clear plastic pre-filter.

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Passo 2

Pull the fuel hose off. Be aware that some fluid will run out of the supply line as you remove the hose. More will flow if you have a full tank of fuel.
Have a plug ready, made using a small length of fuel hose and a tightly fitting bolt.

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Passo 3

Next, loosen the rearmost clamp on the fuel return "cigar" shaped hose that is larger in the middle than the ends. This is the connection to the hard fuel return line that takes unburnt fuel back to the tank.
Remove this line. Little fluid should run out.

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Passo 4

Attach a 12" or so length of 5/16" fuel line on the supply and return lines, using appropriately sized barbed fittings to create hose extensions to make it easier to insert the hoses in your temporary "fuel tank".

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Passo 5

You'll need to create a small temporary "fuel tank" for the diesel purge. Any plastic bottle will work. You'll want to cut a hole in it for the supply hose so that the hose can reach the very bottom of the "tank".

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Passo 6

Fill your temporary "fuel tank" up with the diesel purge fluid.
Now insert the return line in the top of the tank. It can be above the level of the fluid. It will just be pouring fuel back in to the tank.

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Passo 7

Now, start the engine!
Let the car run. It will take in the purge, burn some of it, and return some of it to the tank. As it flows through the system it will clean the system. You may see that the purge comes out darker than it goes in.
As it flows through, any carbon removed from the system will get trapped in the filters.
Stop the car just before the purge goes below the level of the supply line. Do not let your tank run dry or you'll have a hard time removing the air from your fuel system!
After running a purge, it's the perfect time to replace your fuel filters. There are two guides to help with this.
Primary Fuel Filter Replacement
Secondary Fuel Filter Replacement