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Pelican Technical Article:

Fuel Pump Replacement

Steve Vernon

Time:

3 hours3 hrs

Tab:

$200

Talent:

**

Tools:

8mm socket, large claw type wrench, extraction pump

Applicable Models:

Mercedes-Benz ML320 (1998-03)
Mercedes-Benz W203 (2001-07)

Parts Required:

Fuel pump, fuel pump sealing O-ring

Hot Tip:

Use extreme caution working around fuel

Performance Gain:

Better running engine

Complementary Modification:

Replace fuel filter

Replacing the fuel pump on a Mercedes C320 can be done without removing the fuel tank. There is an access panel under the rear seat cushion that allows servicing. To access the pump you will need to first remove the rear seat. Please see our article on removing your seats. A faulty fuel pump can cause poor engine performance and hard starting problems. When they fail completely, you will be left with an engine that doesn't run at all.

It is best to replace your fuel pump with the fuel tank drained. This reduces the amount of possible spilled fuel and fuel vapors. When replacing, work in a well ventilated area, working outdoors is a good choice. Do not use incandescent work lights or power tools and DO NOT smoke, fuel and fuel vapors are highly combustible.

Disconnect negative battery cable.

Remove fuel cap, then slide an anti-static siphon hose down fuel filler neck. Once hose has bottomed out, pump fuel out of fuel tank into an approved storage container. You can refill the tank with this fuel when the job is complete. (If the fuel pump is dead, you can't drain using it. Try Removing the pressure line from the filter on the feed side, then use a pump to pump the fluid out of the tank into a suitable container.)

Make sure you depressure the system through the Schrader valve under the hood of the car. If you disconnect the lines under pressure you will spew gas all over the interior.

The fuel pump is located in the right side of the fuel tank. With the seat removed you will see the access panel to the fuel pump on the right hand side. Remove the six 8mm screws holding it in place and gently pry the panel up. There is a small sticky gasket between the panel and the body of the car to help reduce noise and vibration so do not clean that off.

With the access panel off you can see the locating cover and ring seal on the pump. There is a small arrow on the locating cover that will line up with a mark on the tank when you reinstall the pump. This cover and ring seal hold the pump n place in the tank.

Use a large claw type wrench and remove the ring seal. It is on tight and if you try and unscrew it by tapping the plastic notches with a flat head screw driver you will just shear off the notches.

Remove the ring cover along with the shaped seal. Note how the two female ends in the cover mate with the two male ends on the pump.

Grasp the pump and remove it from the tank.

Take care when you remove the pump and install the new one that you do not damage the fuel level unit attached to it.

With the pump out of the fuel tank: remove the electrical connection, supply line and return line.

Install the lines onto the new pump, connect the electrical connection and installation is the reverse of removal.

The fuel pump is located in the right side of the fuel tank.
Figure 1

The fuel pump is located in the right side of the fuel tank. With the seat removed you will see the access panel to the fuel pump on the right hand side. Remove the six 8mm screws (red arrow, one illustrated) holding it in place and gently pry the panel up. There is a small sticky gasket between the panel and the body of the car to help reduce noise and vibration so do not clean that off.

With the access panel off you can see the locating cover and ring seal on the pump.
Figure 2

With the access panel off you can see the locating cover and ring seal on the pump. There is a small arrow (red arrow) on the locating cover that will line up with a mark on the tank when you reinstall the pump.

Use a large claw type wrench (red arrow) and remove the ring seal.
Figure 3

Use a large claw type wrench (red arrow) and remove the ring seal. It is on tight and if you try and unscrew it by tapping the plastic notches with a flat head screw driver you will just shear off the notches.

Remove the ring cover along with the shaped seal.
Figure 4

Remove the ring cover along with the shaped seal. Not how the two female ends in the cover mate with the two male ends on the pump (red arrows).

Grasp the pump and remove it from the tank.
Figure 5

Grasp the pump and remove it from the tank.

Take care when you remove the pump and install the new one that you do not damage the fuel level unit (red arrows) attached to it.
Figure 6

Take care when you remove the pump and install the new one that you do not damage the fuel level unit (red arrows) attached to it.

With the pump out of the fuel tank: remove the electrical connection (green arrow), supply line (blue arrow) and return line (yellow arrow).
Figure 7

With the pump out of the fuel tank: remove the electrical connection (green arrow), supply line (blue arrow) and return line (yellow arrow).

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Comments and Suggestions:
Alex Comments: Hi, I had posted earlier on 11/3. So, I removed the ring seal and cover underneath the rear seat on the passenger side as shown in this article. Checked voltage to the pump and it gets 12V with key turned run position as well as when cranking over. However I do not hear the pump prime or run at all. This side of the tank is also FULL of gas gauge reads 1/3 tank. Safe bet that this pump is dead?

Is there another pump on the driver side of the tank as well? And if so would the car still not run even if only the passenger side pump was bad? I've found conflicting info on whether or not the driver side tank contains a second pump.

Gonna trust my gut and order the pass side pump assembly, just trying to eliminate the possiblity of another part beig bad. Again it's an '03 C230 M271, cranks but will not start, 0 psi at fuel rail at all times.
November 21, 2016
  Followup from the Pelican Staff: Sounds like a faulty pump. If it is getting power and not turning on. Should be only one pump.- Nick at Pelican Parts  
gina Comments: Meed step by step diy info on removing back seat to get to fuel pump in my 99 MB clk 320 because I'm afraid my man is going to break something
November 3, 2016
  Followup from the Pelican Staff: All articles located here: http://www.pelicanparts.com/techarticles/MBZ_Tech_Index-W203.htm

If what you need sin;t there, you will need a repair manual. - Nick at Pelican Parts
 
Alex Comments: Can you tell me how to test the fuel pump to make sure it really has failed, rather than possibly an issue with some related component that the pump requires to run? I've verified that the pump does not turn on 0 psi at fuel rail at all times, engine starts on starting fluid. Going to pull the rear seat and check voltage to the pump next I suppose, should it be 12V with the key in start and run positions, or some other value? This is an '03 C230 Kompressor M271 by the way.
November 3, 2016
  Followup from the Pelican Staff: Use a gauge, test pressure volume and quality. Then test power (battery voltage) and ground (battery negative voltage) to the pump. - Nick at Pelican Parts  
Mike Comments: Do you have any step by step procedures for replacing the fuel filter and fuel sending unit for a 2009 Mercedes Benz ML320 CDI BluTec Diesel?

Cant find anything in regards to this!
September 28, 2016
  Followup from the Pelican Staff:
We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Jimmy S Comments: Removal - sorry for the typo
September 15, 2016
  Followup from the Pelican Staff: No problem. I make them all the time. The procedure should be similar. - Nick at Pelican Parts  
Jimmy S Comments: I have C320 2005. What is different about the romeral procedure. I have no pressure at the shrader vale
September 14, 2016
  Followup from the Pelican Staff: romeral? - Nick at Pelican Parts  
Robs Comments: My c230k compressor sometimes doesn't want to start after driving around 160km. what could be the problem. Today it flashed the warning signs the signs that come up when I start while it was moving. could this be the fuel pump? please advise me
August 25, 2016
  Followup from the Pelican Staff: I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
 
Country Girl Comments: Hi i just had a fuel pump put in on a 2003 Benz e320 and it started right up cut it off and started up then hour later it hesitated on starting then this morning I go to fill up and after32 $of gas i see it running out from underneath so does that mean machanic didn't seal something or what because DIDN have that issue last week when i put gas in please help
August 18, 2016
  Followup from the Pelican Staff: Sounds like there is a leak. Do not drive the vehicle. Have it towed to the shop and ask them to inspect the leak. A line may have failed coincidentally or something was left loose. - Nick at Pelican Parts  
Snowspyder Comments: I'm doing my homework on replacing the fuel pump. 2001 c240 . Is the info here related to the C240. Like as in a access panel vs dropping the tank? Thanks
August 4, 2016
  Followup from the Pelican Staff: Your fuel pump procedure should be similar. It is located under the same style access panel.


Applicable Models:


Mercedes-Benz W203 (2001-07) - Nick at Pelican Parts
 
Spike Comments: Hi,I forgot to mention, we have to disconnect battery, wait a awhile, a few hrs. then reconnect the battery, then it starts and runs drives normal. Any hints out there? would be greatly appreciated. Mahalo
May 31, 2016
  Followup from the Pelican Staff: This info is helpful. When the vehicle doesn't start, I still need to know what is missing. Also need to know what fault codes are stored. - Nick at Pelican Parts  
Spike Comments: I replaced the fuel pump relay and still the car wont start up normal. It starts up great,then turn it off, then it wont start on second try. It says on display two faults, elec.,stabil, program,not availible,.Do we need to reset the computer, clear faults?
May 31, 2016
  Followup from the Pelican Staff: My first comment remains the same. Check the items I noted.- Nick at Pelican Parts  
spike Comments: we replaced the fuel pump and fuel filter, start her up, engine starts, shut it off,start her up let the engine run, turn engine off. wait about 1 hour, try starting engine, and now it wont start. Disconnected battery then wait about 8hours then connect battery then she starts up? could it be the fuel pump relay?
May 20, 2016
  Followup from the Pelican Staff: I can't help without knowing what is missing from the system when you are trying to start it. When your engine doesn’t start you’ll want to check the basics. Check spark, fuel injector pulse and fuel pressure, volume, quality and engine compression. Are there any fault codes? Once you figure out what is missing, it will be easier to diagnose.
- Nick at Pelican Parts
 
HalfAssedMechanic Comments: 2006 C280
A few notes for DIY mechanics: Because of the situation I was in I had to do the repair with 3/4 tank of fuel, it really was not a problem. I was able to get the lock ring off by tapping it with a large screwdriver, very slowly, with a rubber mallet. I never found the Schrader valve so I wrapped a paper towel around the top fitting and just popped it off, no problem. Finally, the reassembly goes much better if you take the sealing ring off the cover and fit into the top of the and then slide the cover into it. This repair was much easier than I anticipated.

March 26, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Karim Comments: How do I remove the back seats to access my fuel pump in a 2002 clk320?
March 24, 2016
  Followup from the Pelican Staff: I believe on your model, it is accessed through the trunk. Remove the carpet trunk panel, then the metal panel behind the rear seats. - Nick at Pelican Parts  
jneelddesigns Comments: Your beginning how to states "Remove fuel cap, then slide an anti-static siphon hose down fuel filler neck. Once hose has bottomed out, pump fuel out of fuel tank into an approved storage container." The design does not allow a siphon hose down past the neck. Not sure how to drain the fuel from the vehicle. I had the filter off changing it and I barely got any fuel out of those four hoses. Just filled up prior to the no start issue.
January 26, 2016
  Followup from the Pelican Staff: If the fuel pump is dead, you can't drain using it. Which is method I have used in the past. Remove the pressure line from the filter on the feed side, then use a pump to pump the fluid out of the tank into a suitable container.- Nick at Pelican Parts  
Joejo Comments: Where is the schrader valve; and how do I depressurize the system? Can you give me a picture? 2003 mb c320 4matic wagon. Is there also a pump on the left side?
January 11, 2016
  Followup from the Pelican Staff: I don't have a photo. Check the fuel rail for the Schrader valve. - Nick at Pelican Parts  
Vito Comments: Hi,
Do you know where the fuel pump for 2000 Mercedes E320 W210 located? The fuel tank is behind the rear seats, but where is the pump? It's not under the car!
Thanks
November 3, 2015
  Followup from the Pelican Staff: It is under the vehicle. Mounted near the differential. - Nick at Pelican Parts  
Jab Comments: my pump doesn't syphone the left tank. the car only run with the right tank. what can I do.
October 9, 2015
  Followup from the Pelican Staff: Replace the siphon and hoses to both sides of the pump. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
kevin Comments: oh, another question.
I can not get the unit out of the tank. It seems the wires are not long enough. Thanks for any advise
August 25, 2015
  Followup from the Pelican Staff: The wires stay attached to the unit, they shouldn't run through the tank. - Nick at Pelican Parts  
kevin Comments: having a tough time putting the ring seal back on.
any suggestins
August 25, 2015
  Followup from the Pelican Staff: The seal goes into the tank first, then the unit slides into it. - Nick at Pelican Parts  
john Comments: Is this same for c 230 kompressor
Comments: Is this the same with C 230 kompressor 2005 model with sport package?
April 14, 2015
Followup from the Pelican Staff:
Applicable Models:
C320 1998-2004
E320 1998-2004
S320 1998-2005
ML320 1998-2003
CLK320 1998-2004
SLK320 1998-2003 - Nick at Pelican Parts
July 16, 2015
  Followup from the Pelican Staff: Coverage stops at 2004 for the article. - Nick at Pelican Parts  
Berger Comments: Make sure you depressure the system through the Schrader valve under the hood of the car. If you disconnect the lines under pressure you will spew gas all over the interior.
May 25, 2015
  Followup from the Pelican Staff: I agree 100%.

Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
jojo Comments: Is this the same with C 230 kompressor 2005 model with sport package?
April 14, 2015
  Followup from the Pelican Staff:
Applicable Models:
C320 (1998-2004)
E320 (1998-2004)
S320 (1998-2005)
ML320 (1998-2003)
CLK320 (1998-2004)
SLK320 (1998-2003) - Nick at Pelican Parts
 
jojo Comments: This is awesome, good well explaination and good pics too.
April 14, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Funhockey Comments: The problem I've had was that the new pump has a black electrical connector. That doesn't fit on the original wiring harness going to the sending unit. Located on the drivers side. Which has a white electrical connector. I'm told that I'm suppose to replace the sending unit as well. Which the new sending unit will have a black connector. But there's nothing wrong with my sending unit. So I decided to swap connectors from the old pump to the new pump. And it works. My C320 runs!
You just have to careful and pull off the positive and negative wires from the two pumps. And the two green or blue wires from the float unit. And I zip tied the white connector on to the new pump. By drilling a hole on the flanges where the black connector sat on. Then the new pump with the old electrical connector is good to be installed. And save yourself the cost of having to replace the sending unit.
August 10, 2014
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it. - Nick at Pelican Parts -  

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