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Pelican Technical Article:

Fuel Pump Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$300

Talent:

*****

Tools:

Flathead screwdriver, 8mm socket, fuel pump collar tool

Applicable Models:

Mercedes-Benz W211 (2003-09)

Parts Required:

Fuel pump, fuel pump sealing O-ring, fuel pump collar

Hot Tip:

Clean top of fuel tank before removing pump

Performance Gain:

Repair faulty fuel pump

Complementary Modification:

Replace fuel filter

In modern Mercedes-Benz automobiles the fuel pump is electric and located inside the saddle-fuel tank. The fuel pump creates positive pressure in the fuel lines, pushing gasoline to the fuel rail, where the DME controls fuel flow to the engine via a programmed fuel injection map. In tank fuel pumps have many benefits. The fuel is submerged in fuel keeping it cool, preventing vapor lock and electrical issues. The fuel pump delivers a constant flow of gasoline to the fuel pressure regulator, located in the left side of the fuel tank. The fuel then flows to the fuel rail at a regulated pressure and volume.

A faulty fuel pump can cause poor engine performance and hard starting problems. When they fail completely you may be left with an engine that doesn't start. If you suspect your fuel pump has failed, you can confirm the fuel pump is received the correct voltage when commanded ON by the fuel pump relay using a digital volt ohm meter (DVOM). See our tech article on fuel pump testing.

Replacing the fuel pump on a W211 can be done without removing the fuel tank. The fuel pump is located in the right side (passenger side) of the fuel tank. There is an access panel below the passenger seat cushion. Even though the fuel pump is located in the right side of the fuel tank, the electrical connector is on the left side, under the access panel for the fuel filter. When replacing the fuel pump, all work will be performed on the right side of the tank.

Remember that your car may have been serviced before and had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

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. Fuel and fuel vapors are highly combustible.

Drain your fuel tank. Run the vehicle for about 20 seconds. This equalizes the amount of fuel in the siphon unit.

Disconnect the negative battery cable. See our tech article on battery replacing and reconnecting notes.

Remove the fuel cap. Then slide an anti-static siphon hose down the fuel filler neck. Once the hose has bottomed out, pump fuel out of the fuel tank into a suitable storage container. If you are unsure of the amount of fuel in your tank, you can monitor the fuel level via the fuel level sender units. As the fuel level drops, the fuel level sender resistance drops. You can measure this across the terminals at both sender units with a digital volt / ohm meter (DVOM). You will need a wiring diagram from a repair manual.

Start at the right side seat cushion.
Figure 1

Start at the right side seat cushion. In front of the cushion is a small plastic release lever. Pull the lever up to release the seat cushion latch.

Fold the seat cushion forward.
Figure 2

Fold the seat cushion forward. The right side is shown. Repeat these steps for the left side.

With the seat cushion folded forward, remove the carpet from below the seat.
Figure 3

With the seat cushion folded forward, remove the carpet from below the seat. Pull it up at the corner to detach the clip (red arrows). Pull the carpet out from under the plastic trim (green arrow). The right side is shown. Repeat these steps for the left side.

Peel the carpet away from the body floor and support it out of your way.
Figure 4

Peel the carpet away from the body floor and support it out of your way. I have mine propped up with a steering wheel holder (red arrow). Even though the fuel pump is located in the right side of the fuel tank (green arrow), you will have to peel away the carpet to expose both access covers.

Remove the six 8mm access cover fasteners (red arrows).
Figure 5

Remove the six 8mm access cover fasteners (red arrows). Then lever the access cover up and remove it. (inset).

Next, you have to unscrew the fuel pump module threaded collar (red arrow).
Figure 6

Next, you have to unscrew the fuel pump module threaded collar (red arrow). There is a special tool made to do this. The tool has notches that match the teeth on the collar. Loosen and remove the collar.

However, if you do not have this tool you can use a brass punch and a rubber mallet.
Figure 7

However, if you do not have this tool you can use a brass punch and a rubber mallet. Using the brash punch and a rubber mallet, tap the threaded collar on one of the ridges counter-clockwise to loosen. Once loose, unscrew the remainder of the way by hand. If the collar is damaged during this process, you will need to replace it with a new part.

Remove the collar from the fuel tank and store it in a safe place.
Figure 8

Remove the collar from the fuel tank and store it in a safe place. Gently lever the top of the fuel pump module up to free it from the tank seal (green arrow).

Slowly lift the fuel pump module top up and remove it.
Figure 9

Slowly lift the fuel pump module top up and remove it. Then pull the seal out of the fuel tank (green arrow).

Next, you have to remove the lines and electrical connectors at the fuel pump module.
Figure 10

Next, you have to remove the lines and electrical connectors at the fuel pump module. Press the release tab (red arrow) and pull the electrical connector straight out to remove it. Then, press the release tab (green arrows) in toward the line and hold it. Then slide the line off the fuel pump module.

Next, you have to remove the lines to the fuel pump housing.
Figure 11

Next, you have to remove the lines to the fuel pump housing. Pull both lines (red arrows) straight out of the holders and lay them aside.

The level sender has to be detached from the fuel pump module to fit it out of the fuel tank.
Figure 12

The level sender has to be detached from the fuel pump module to fit it out of the fuel tank. Spread the black retainers (red arrows) to release the tab (green arrow) and slide the level sender up out of the module to remove it. Feed the level sender out of the fuel tank. I leave it connected to the fuel pump module during the part. Be careful not to bend or damage the sending unit.

Slowly lift the fuel pump up slightly out of the tank, then remove it straight up.
Figure 13

Slowly lift the fuel pump up slightly out of the tank, then remove it straight up. Have a bucket or plastic bin inside the vehicle with you. Catch any dripping fuel with a cloth as you remove it. Then immediately place the fuel pump module in the bucket to minimize spilled fuel.

Remove the fuel lever sender (red arrow) from the old fuel pump module.
Figure 14

Remove the fuel lever sender (red arrow) from the old fuel pump module. Disconnect the electrical connectors (green arrow), noting their position. Then transfer them over to the new fuel pump module. Slide the new fuel pump module into the fuel tank. Then attach the fuel level sender to retainer and position the module in the tank so the line connections are facing the left side of the vehicle. Reattach the fuel lines and electrical connector to the fuel pump module. Hand-tighten the threaded collar. Then tap it tight (clockwise) with the brass punch and a rubber mallet. Fill the fuel tank with about 2 gallons of fuel before attempting to start. Once you are sure that the fuel pump is operating normally, fill the remainder of the fuel tank and check for leaks. Once done, reassemble the interior.





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Comments and Suggestions:
steve Comments: Many thanks.. just bought a second hand pump for $75 and fitted myself following these instructions.
October 28, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Ian Comments: Great write up. I was able to complete this in about an hour today, partly because I had already gone through he testing procedure. The clips on the new pump were too big for the standard fuel lines but they seemed to stay where they were supposed to. The new VDO pump also included the fuel level sending unit. One tip, I wasn't able to get a siphon tube into the tank through the filler neck but once I opened up the cap I was able to siphon out most of the fuel at that point. Don't open up the pump if you have more than a half tank or fuel will spill out.
October 27, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Nazar Comments: I have a MB E350 W211 2008 model.. Problem is that fuel pump is built in was told have to order a complete new fuel tank.. any ideas?
October 25, 2016
  Followup from the Pelican Staff: Could be depending on emission controls. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Fidel001 Comments: My MB 2006 E350 4MATIC sometimes during a trip starts to jerk as if its aspirating. The car refuses to be sluggish and not respond to acceleration. Then i release my feet from the accelerator and place it lightly to glide me from dangerous spots. i them have to wait for about 45minutes before driving off again. now with low speed.

What do you think is wrong with the car?
My mechanic says i need to change the fuel pump and fuel filter.

Is this right?
October 24, 2016
  Followup from the Pelican Staff: Is the check engine light on or flashing when the problem is present? Sounds like an engine misfire. I would check spark, fuel and compression on all cylinders.
- Nick at Pelican Parts
 
Seemore Comments: there is a transfer pump in the drivers side along with the fuel filter. The main fuel pump is on the passenger side. My car quit on the interstate whith what my fuel gauge said 1/4 tank. Checked fuel pressure and there was none. opened both sides of the fuel tank and the passenger side was empty but the drivers side had a 1/4 tank. the transfer pump moves fuel over the driveline hump in the fuel tank. Why else would they have 3 hoses from the drivers side to the passenger side.
September 13, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
Julius Comments: how do i find out if the fuel pump is working right, now i have taken it out
August 30, 2016
  Followup from the Pelican Staff: You can momentarily power it up, but don't it for more than a second, it could fail without fuel to lubricate it. Be sure it is dry and free of fuel fumes first. Do not power it up near the any fumes or fuel.- Nick at Pelican Parts  
Jem Comments: 2007 M-B E350 - is fuel pump on passenger or driver side ?
August 23, 2016
  Followup from the Pelican Staff: Left side (driver). - Nick at Pelican Parts  
Tim Comments: In my e320 on the drivers side is it a pump or a filter? Does this pump or filter come as a unit? I want to replace it when I replace the fuel pump which seems to be on the passenger side.

Thanks

Tim


August 22, 2016
  Followup from the Pelican Staff: Filter:

http://www.pelicanparts.com/techarticles/Mercedes-W211/78-FUEL-Fuel_Filter_Replacement/78-FUEL-Fuel_Filter_Replacement.htm

Pump:

http://www.pelicanparts.com/techarticles/Mercedes-W211/78-FUEL-Fuel_Filter_Replacement/78-FUEL-Fuel_Filter_Replacement.htm - Nick at Pelican Parts
 
Puddib Comments: Yes I have 2006 Mercedes Benz E500 the dealer told me I need a fuel pump & that my fuel tank was not leaking to replace the fuel pump wouldn't the tank have to have a leak ?
August 17, 2016
  Followup from the Pelican Staff: No, the top of the fuel pump can leak. - Nick at Pelican Parts  
Terje Oseberg Comments: Marc, there is no pump on the driver's side. That's the fuel filter.

Also, it appears that the PZEV version of the W211 has no access port on the passenger side of the fuel tank, and I still have no idea where the fuel pump is, or how to replace it. The fuel filter is still on the driver's side and appears to be unchanged.
May 14, 2016
  Followup from the Pelican Staff: What vehicle are you working on? I can see if I have the info you need. - Nick at Pelican Parts  
Marc Comments: What is the function of the pump on the driver's side, and does it need to be replaced at the same time as the pump on the passenger's side.

Thanks
March 30, 2016
  Followup from the Pelican Staff: What pump, what vehicle? - Nick at Pelican Parts  
Steven Comments: Dealer wanted $1,700 and said they needed to remove the axle and drop the gas tank... Thanks to your article, I did the job myself in 20 minutes for less than $200...
March 25, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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