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2000 E430 4Matic, 2007 R320 CDI, 2012 E63 P30, 2013 SLK250
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Discussion Starter #1 (Edited)
performed this R&R last November. Meant to post this earlier but didn't get a chance to do so until now.

Tools:
1. Torx sockets for seat removal. Don't remember the size...
2. heat gun
3. pry bar or something to pry the floor cover off.
4. Hammer and drift

Parts:
1. 1644700230 pump seal ring (1)
2. A2514700994 low pressure fuel lifter pump (1)
3. Gasket sealant (1)

Before attempting this R&R, make sure you tank is at least half empty. It makes it easier and cleaner when you remove the pump.

First off, this pump is the low pressure lift pump that brings the diesel to the main HP pump that sits on the motor. Because this pump is situated before the fuel filter and is electronic, it seems to be prone to failure especially when the fuel filter starts to get clogged. Official fuel filter replacement intervals for the CDI is every 20K miles. I would recommend doing it at 15K in attempts to prolong the operating lifetime of this pump.

Now on to the procedure:

1. First, disconnect the SRS wire of the passenger side middle row seat. Then slide plastic bolt covers out and away from the seat and remove middle row seat by unbolting the 4 seat bolts.

I used a flat head driver to pry and slide:


slide this way:

(in hindsight, I should've used something made of hard plastic to avoid scratching the cover, but once you do it once and know how it goes, you probably won't scratch it the second time.

2. lift floor carpet.
Some people remove it all together. I peeled it back and used something heavy to hold it down once folded over. You will see the cover to the fuel pump:

(this pic shows the seal glue already removed).

3. Next, use a hot air gun to soften the seal around the cover shown above. This step is the most time consuming and most annoying. You MUST soften the glue, otherwise, it will be almost impossible to pry off, not to mention you may deform the cover if you just ham-fist the cover before removing ALL the glue.

4. Pry off cover as shown in pic in the above step.
now you will see this:


5. Disconnect the wire harness:

Before moving further, I would suggest covering the surrounding area to protect the interior from diesel splashes. You don't want to smell diesel forever when you are driving.

6. Remove fuel pump cover ring.
This step as shown in WIS requires a special socket which allows you to twist the cap ring off. Someone even fabricated a tool using a wooden disk and metal L brackets. I used a much easier method:



Use a flat tipped drift and hammer to turn the ring. It's actually quite easy once you give it a go. Just make sure the drift you are using is something with a large flat surface area and not sharp as to break the plastic fins of the ring. Each impact will result in about an 1/8th turn. Continue doing this until you can turn the ring by hand. The pump unit is spring loaded to push up against the ring, so you need to push the center of the pump unit down to reduce the rotating friction before you will be able to turn by hand.

7. once you have the ring off, the pump will pop up if you are not holding it down. This is where you want to make sure you are applying pressure to the top before unscrewing the ring all the way as some diesel will spash when it pops up and you want to avoid it popping up.

8. Disconnect the two fuel hoses and lift the pump out of the fuel tank and replace.



Note how all the wires/hoses are routed and reinstall the same way. Note where the fuel intake bracket is and how the metal bracket is secured to the pump body when removing:



When reinstalling the seal ring, it might be helpful to have someone push down on the pump while the other tightens the ring. The last half turn is difficult especially when the pump is pushing up against the ring, creating more friction. (the ring has markers to indicate correct tightness)

9. Connect SRS wire from seat and test drive. (the reason for this is that if you test drive without the SRS connected, the computer will throw a SRS fault. The only way to clear it is with a STAR computer.)

10. Finally, once you confirm there are no leaks, apply gasket seal to floor cover and replace.

Turn the key to pre-ignition position and hear the low pitch hum of your new pump!

-Robert
 

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2007 ML320 CDI
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I did my own pump change on my ML320 CDI. Did you have any fuel quantity indication problems ? Shortly after I did mine the fuel gauge started acting up. It only goes up to 3/4 of a tank and sometimes dies all together.
 

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2000 E430 4Matic, 2007 R320 CDI, 2012 E63 P30, 2013 SLK250
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440 Posts
Discussion Starter #3
I did not have any fuel gauge problems. I believe the fuel level sender is under the driver side middle row seat (opposite of the fuel pump). I did not access that portion of the fuel tank for this R&R.

-Robert
 

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Foaming fuel returning to Fuel Delivery Unit ML320 CDI W164 at work

:confused:Hi. Following your precious instructions to access the pump I've replaced the Fuel Delivery Unit part#1644702094 by another with #1644700394. The old one was very high pitch noisy and gave me two CEL lately so I decided to anticipate the roadside risk and made the change DIY. Before closing the unit I decided to test, hearing and seeing it while working.
This is what happens inside:
Is it normal the foaming fuel returning by the hose that is clipped on the unit housing, or I have a fuel line issue? Txs.:confused:
 

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2000 E430 4Matic, 2007 R320 CDI, 2012 E63 P30, 2013 SLK250
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440 Posts
Discussion Starter #5
I can't tell you if the foaming is normal or not, as I've never run the pump with the cover removed. It is possible that air is being introduced, which otherwise wouldn't with the cover in place.
How did you determine the CEL to be related to the low pressure (FDU)?
Are you still having CEL issues after replacement using the updated part?
Are you having any other symptoms?

-Robert
 

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07' R350, 03' Jaguar STR, Recently acquired 03' s55 AMG
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49 Posts
Is this the same procedure as a 09 Gl320 Bluetec?

HI Chucelli,

I think Im running into the same problems as you have with my 09' GL320 Bluetec. NO codes at all, just cranks but doesn't stay started. Dealer is clueless,wants close to thousand dollars to try to figure out the cause. I'm perplexed also why its not staying started. My indy thought it could be a clogged fuel filter, so he changed it out, but still back to square 1. Dealer mechanic at Mercedes, the one who suppose to be the specialist in diesel said he see's the fuel coming out if he turns the black breather valve ontop of the fuel filter, but thinks something is going on the fuel rail and is basically clueless!! :frown,
My question to you is, if you have any idea if the location of the "LPFP" lower pressure fuel pump is located in the same area as the R320 CDI like yours? Also, I would be very grateful if you had any info to share on what to look out for etc....
Thank you in advance!!
 

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2000 E430 4Matic, 2007 R320 CDI, 2012 E63 P30, 2013 SLK250
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440 Posts
Discussion Starter #8 (Edited)
Hi Merc79,

according to EPC, the location of the LPFP is in the same place under the rear (middle row) passenger seat.
Just to be clear, your car starts but then shuts off? Or does it just crank and crank without starting?

The LPFP can be heard when the ignition is turned on to the pre-start position. If you can hear a low pitched drone before initiating engine start, then the LPFP is most likely working. Based on what you said, if the car started, then fuel to the high pressure pump stopped, you should get a code. If no fuel gets to the high pressure pump at all before starting the engine, you would not get any codes.
If however, your car is just cranking and not starting at all, and you are getting no codes, then most likely fuel is not getting to the high pressure pump. Since you've already replaced the fuel filter, there's no reason to suspect a clog. As for seeing fuel after removing the black nipple on top of the fuel filter, I'm not sure that means anything. There will most likely be residual fuel inside the fuel filter even if the pump is not working at that moment. Its also possible that you have an issue with the relay that controls the LPFP. If you are not sure what the LPFP sounds like, I would suggest finding and pulling the LPFP relay to see if there is any difference in the sound when the ignition is at the pre-start position. With the relay pulled, you won't hear anything.
As far as I know, the only thing that could cause this engine to crank and not start with no codes is lack of fuel to the high pressure pump. If you had a fault with any of the sensors (such as crank shaft position, you would get a code and the engine would not crank at all). In my case, my LPFP was completely dead and made no noise at all, so it was easy to determine the issue.

Good luck,

-Robert
 

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07' R350, 03' Jaguar STR, Recently acquired 03' s55 AMG
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49 Posts
Hi Merc79,

according to EPC, the location of the LPFP is in the same place under the rear (middle row) passenger seat.
Just to be clear, your car starts but then shuts off? Or does it just crank and crank without starting?

The LPFP can be heard when the ignition is turned on to the pre-start position. If you can hear a low pitched drone before initiating engine start, then the LPFP is most likely working. Based on what you said, if the car started, then fuel to the high pressure pump stopped, you should get a code. If no fuel gets to the high pressure pump at all before starting the engine, you would not get any codes.
If however, your car is just cranking and not starting at all, and you are getting no codes, then most likely fuel is not getting to the high pressure pump. Since you've already replaced the fuel filter, there's no reason to suspect a clog. As for seeing fuel after removing the black nipple on top of the fuel filter, I'm not sure that means anything. There will most likely be residual fuel inside the fuel filter even if the pump is not working at that moment. Its also possible that you have an issue with the relay that controls the LPFP. If you are not sure what the LPFP sounds like, I would suggest finding and pulling the LPFP relay to see if there is any difference in the sound when the ignition is at the pre-start position. With the relay pulled, you won't hear anything.
As far as I know, the only thing that could cause this engine to crank and not start with no codes is lack of fuel to the high pressure pump. If you had a fault with any of the sensors (such as crank shaft position, you would get a code and the engine would not crank at all). In my case, my LPFP was completely dead and made no noise at all, so it was easy to determine the issue.

Good luck,

-Robert
Hi Robert,

Thank you soo much for replying back and sharing your suggestions. Sorry for replying late, as I was out of the country, and just got back. The Gl320 is still at the dealer for airbag recall on the driver side. I mentioned to the tech of what you suggested and lets see what he says hopefully by this weekend. As to your question, yes it cranks without starting. I believe you hit the nail on the coffin when you stated "only thing that could cause this engine to crank and not start with no codes is lack of fuel to the high pressure pump" Thats definitely a possibility. I will update as soon as I get word, thanks again to you and this wonderful forum!

Cheers!
Tarek.
 

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E 280 CDi
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Different mercedes same problrm

Hi Robert,

Thank you for the informative procedure. My car is 2005 E280CDi (European) with 3.2 engine. The problem is cranking but not starting. The codes I got from a generic OBD2 are exhaust sensors (oxygen and DPF but I was told they don't cause a no start) but I don't trust that cheap scanner. I replaced Cam Position Sensor and the difficult-to-reach Crank Position Sensor but the problem remains. Before I surrender to the dealer, I would like to replace the LPFP. My question is if I pull out the supply line off the filter and put in pressurized diesel line instead just for testing; do you think this is acceptable way to verify the status of the LPFP? I trust your opinion.
 
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