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Discussion Starter #1 (Edited)
DIY - Fuel Pump, Remove & Install

INSTRUCTIONS FOR REPLACING THE FUEL PUMP

1) Remove flaps of the rear seats. See the first picture for location of access site.
2) Remove rear seat bottom covers. There are no screws, just tabs. Releasing the tabs is the most challenging step. You can easily brake the tabs. See detailed instructions in pdf about this. See picture for under surface of the cover.
3) Unscrew rear seats. There are two hex nuts and several torx bolts. Disconnect the SRS cables; one for each seat.
4) First, remove 40% seat (rear passenger side) from the car.
5) 60% seat is very heavy. Just slide it to the location of 40% seat so that you can work on the driver side.
6) Fold the floor mat (driver side corner) and you will see the a round cap covering the access hole. Cap is attached to the body by sealant only.
7) Remove the seal and lift the cap. You will see top of the fuel pump. Take a picture to document the alignment of the pump connections. See picture
8) Unplug the cable which is power line to the pump.
9) Start engine and wait 5-10 seconds until engine runs out of fuel and stalls.
10) Disconnect the fuel lines. Push the line, press the tabs on each side with your fingers and remove it.
Caution: The fuel line in the center (feeding line) is still pressurized from the fuel filter which stores almost 1/2 quart of remaining fuel. Collect the fuel into a cup immediately after disconnecting the line. Fuel will come from the line, not from the pump. There will be some fuel spill, so place towels around. This will minimize inhalation of the fuel vapor.
11) Turn the locking ring of the pump counterclockwise and remove it.
12) Lift the fuel pump. It won't come straight up because of the fuel sensor floating arm and secondary intake line (tail-like extension tube). Tilting and turning will be enough.
Caution: There is some fuel inside the pump reservoir (the bottom pan). Tilting the pump more than 45 degrees may cause fuel spill.
Caution: Be careful not to drop anything inside the tank at this point.
13) Carefully insert the new fuel pump. Check the alignment of the fuel lines and make sure it is same as the original.
Caution: Wrong alignment of the pump may prevent fuel sensor floating arm to be lifted completely when the tank is full. Therefore the fuel gauge will never show full tank.
14) Make sure that the rubber gasket has a tight fit between the pump and the tank. Otherwise it may cause a leak when tank is full.
15) Put the the locking ring over the pump and draw a line with a pen (mark initial position).
16) Turn the locking ring clockwise for at least 360 degrees (one full turn). If you have the specific MB tool to remove&install the locking ring, the specification is 65Nm. If you don't have the specific tool, make sure it is tight enough or one full turn. Otherwise it may cause a leak when tank is full.
17) Snap the fuel lines in place. Refer to the picture to confirm the feed line which plugs into the center. Plug-in the power cable.
18) Start the engine.
19) Use body sealant to seal the cap. See picture
20) Install everything in reverse order. Do not forget to connect the SRS cable. Use Loctite for the seat nuts and bolts (40 Nm).

Warning:
- There is risk of explosion by fuel igniting and risk of poisoning by inhaling vapor, eye or skin contact with fuel.
- In order to minimize fuel spill, have minimum amount of fuel in the tank during the procedure.
 

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The procedure lacks detail how to install the gasket. I put the pump in with the gasket on it and the tank rim folded it, what wasn't visible till I fill her up.
Finally I installed it with gasket slided over the float arm, then when float was inside the tank, I put the gasket in the hole and than put the pump all the way in.
Some members reported being able to remove the pump with folding the seats and not removing them.
 

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Discussion Starter #3
The procedure lacks detail how to install the gasket. I put the pump in with the gasket on it and the tank rim folded it, what wasn't visible till I fill her up.
Finally I installed it with gasket slided over the float arm, then when float was inside the tank, I put the gasket in the hole and than put the pump all the way in.
Some members reported being able to remove the pump with folding the seats and not removing them.
Yes, you can put the gasket to the tank first and then slide the pump inside. However, there is the risk of pushing the gasket into the tank so take your time if you prefer this. If I get into the slightest details, it might be confusing more than being helpful. I thought most forum members here should be able to judge positioning of a gasket.

I tried folding seats forward but they would not stay. Those forum members never posted how to do this. Besides I don't think there will be enough space to work. So I decided to remove 40% seat out and slide the 60% sideways.
 

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Excellent post Merzatt!. thanks
 

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Excellent DIY:thumbsup:. Hopefully I will never have to change mine but with 120K on the ODO it could happen at any moment. This needs to be bookmarked for everyone to use. Again, thanks for the write up and the pictures. You make it seem like not such a big deal. Too bad you haven't done a write up on the fuel filter retrofit:(.
 

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Discussion Starter #7 (Edited)
Excellent DIY:thumbsup:. Hopefully I will never have to change mine but with 120K on the ODO it could happen at any moment. This needs to be bookmarked for everyone to use. Again, thanks for the write up and the pictures. You make it seem like not such a big deal. Too bad you haven't done a write up on the fuel filter retrofit:(.
I didn't have to do fuel lines upgrade. But, it shouldn't be too difficult to upgrade the fuel filter and lines together with the fuel pump, as long as you have skinny hands to reach the filter as seen in the picture, it is a bit hiding behind the body.

Most people report trouble with disconnecting the fuel lines. If you cannot do it by hands, you can buy Klann Fuel Line Pliers Mercedes M-Class online for $59
163 589 00 37 00
.

Once you opened the access cover to the fuel pump, feel free to do the upgrade by looking at the diagram and actual picture from my car below. Remember that the feed line is pressurized with fuel. Expect some fuel leak if you are disconnecting this end first.

Remember to start the engine and check the system for leaks when you are done. Hope this was helpful.
 

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Thanks for the fuel filter replacement information. Do you have to remove the seat and pull back the carpeting to access the top of the fuel pump to replace the fuel line during the filter change or can you access them from the wheel well? Thanks again.
 

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Discussion Starter #9
Thanks for the fuel filter replacement information. Do you have to remove the seat and pull back the carpeting to access the top of the fuel pump to replace the fuel line during the filter change or can you access them from the wheel well? Thanks again.
Plano, unfortunately you cannot access the fuel pump from the wheel well. But there is nothing tricky about this job unless you are replacing the pump. It just takes time and patience to reach the access cap.
 

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On my '98 ML320, on the bottom of rear seats, there are no plastic covers (as discussed above). MB didn't put those covers on 98 MY or they are missing on my truck?
 

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Thank you so much. You saved me a ton of money! I bought a used pump at a great salvage yard in Sacramento for $110. My baby is back to great. 257K miles and going.
 

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Nice post. I have 01' ML430 .Where do you recommend buying fuel pump? Also concerned about having to change fuel lines/filter once I get into the job. Independent shop said he had no "notes" on having to upgrade filter/lines at same time.
 

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On my '98 ML320, on the bottom of rear seats, there are no plastic covers (as discussed above). MB didn't put those covers on 98 MY or they are missing on my truck?
My 98ML does not have those covers either. 98 model did not come with covers.
Mike
 

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Excellent post. I have 01' ML430 .Where do you recommend buying fuel pump? Also concerned about having to change fuel lines/filter once I get into the job. Independent shop said he had no "notes" on having to upgrade filter/lines at same time. Also I posted this deeper in thread, but thought I'd try this too.
 

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yep good post, this is exactly how the (indy) dealer did mine when I first bought it and discovered it leaked when full.

A point to note though...
With mine the problem was the lock-ring, it had gone very slightly oval in shape, so wasn't sealing properly even with a new gasket. So had to get a new lock ring as well.
 

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Discussion Starter #17
Excellent post. I have 01' ML430 .Where do you recommend buying fuel pump? Also concerned about having to change fuel lines/filter once I get into the job. Independent shop said he had no "notes" on having to upgrade filter/lines at same time. Also I posted this deeper in thread, but thought I'd try this too.
There are many low cost online stores e.g. AutohausAZ or your dealer if you can afford. If you did not change the filter more than 60k miles, I recommend doing it at the same time because it is so much easier to remove the filter. If last 6 digits of VIN number is less than 265965, you will need an upgraded filter and fuel lines.
 

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Hello all,

I am a new member who acquired a '99 ML430 from his parents who drove it to church & on vacations.

125k miles in March. So I purchased torx tools for whatever might develop before leaving Memphis (back to Atlanta a few months ago), when I noticed fuel pump relay problems/burn out.

I followed instructions for replacing the fuel pump exactly, and still will not crank. Motor turns over fine, just not receiving fuel it appears.
Had a final stall while motor was idling at a traffic light. Previously experienced hesitation also, but relays pushed me to do the fuel pump replacement.

I'm clueless (more so) now.
 
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