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Replacing the Gasoline Fuel Filter

on the 1987 300E (W124)

by Hydronuclear


DIY W124 Gasoline Fuel Filter Change (two fuel pump models)

WARNING: Make sure to support the car with jack stands, do not smoke, etc.

1. Gather your supplies and tools.

a. Safety goggles and rubber gloves.
b. Fuel Filter (w/2 copper gaskets).
c. Plastic bin and towel to catch excess gasoline.
d. 10mm socket with an extension + ratchet.
e. One 13mm, one 19mm, and two 17mm wrenches.
f. Crescent (adjustable) wrench (if not using a German made filter).
g. Fire extinguisher.
h. Phillips screwdriver (maybe).
i. Floor jack and jack stands or car ramps.
j. Wheel chocks.

2. Secure the car with a wheel chock in the front and rear of the driver’s side front tire.


Back up the rear of the car onto car ramps, engage the parking brakes, THEN secure the front tires and proceed to step 4.

3. Jack up the rear of the car (using the differential as a jacking point) and place jack stands under the appropriate jacking location (under the pad beneath the round jacking points). SLOWLY lower the car onto the jacks.

As yet ANOTHER alternative method, lkchris writes “I could do mine simply with right wheels up on a curb. No jacks, that is.”

4. Pop the hood and disconnect the negative battery terminal with a 13mm wrench.

5. Open up the gas cap to relieve the pressure in the tank, then close it back up.

6. Get under the car with your ratchet, extension, and 10mm socket. There are 4 plastic nuts that hold up the cover that conceals the fuel pumps and filter. Remove them.

7. Take a good look at your fuel filter system. Fuel comes from the tank, hits the fuel pumps travels to the fuel filter then the accumulator. Fuel travels through the fuel filter and egresses out to a rubber fuel line that heads to a hard line which takes the fuel to the front of the vehicle. Most of the info I had read stated that you need to “pinch off” these rubber fuel lines to prevent excessive gasoline loss. WARNING: I didn’t pinch them off (they looked old and brittle) and I lost only a minimal amount of fuel (mostly from the filter itself). I do not guarantee that if you tried it that you won’t drain your tank. My assumption is that the fuel pumps effectively blocked the gas from the tank. If you’d like to do this the right way, get these hose pinchers

8. Put the plastic bin under the fuel filter.

9. Fit the 19mm wrench to the base of the front of the fuel filter (If it’s not a German made filter, it should be about 19-20mm. Use a crescent wrench if you don’t have the right size ). Using a 17mm wrench, open up the end cap of the banjo bolt to relieve pressure then loosely re-tighten.

10. Go to the rear of the filter and use two 17mm wrenches to loosen the nut that connects the fuel line to the filter.

11. Now, using the cap that came with the new filter, undo the rear fitting and plug the old filter.

12. Check and see if the strap that holds the filter in place is tightened by a screw (mine wasn’t). If so, loosen the screw.

13. Go back to the front of the filter and undo the banjo bolt. After it comes off, watch out for the two copper gaskets that will likely fall into the plastic bin. Cap off the old fuel filter with the plastic cap from the new one.

14. Push the old filter out towards the rear of the car.

15. Inspect the condition of insulating plastic sleeve that fits between bracket/strap and the filter. Replace it if worn out, fit one if missing.

16. Install the new filter and connect the fuel line to the rear of the filter. Tighten it.

17. To secure the front of the filter to the banjo bolt, make sure you replace the old copper washers with the new copper washers that came with the filter. Tighten it back up.

18. Tighten the strap that holds the filter (if applicable).

19. Get out from under the car, re-connect the negative cable to the battery and crank the car until it starts up. It’ll take a few tries since it will have to purge the air in the fuel lines.

20. Once it cranks up, leave it running and go to the back of the car. Visually check the fuel filter connections to ensure that it’s not leaking.

21. If it looks good, turn the car off, then re-attach the cover with the four plastic nuts.

22. Remove the chocks and drive the car off the ramps.


Raise the car, remove the jack stands, lower the car and remove the chocks.

23. Test drive the car to note any new problems that you need to fix!

Thanks lkchris for filling in the gaps!


Discuss this DIY here.


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