How to replace fuel pumps on m103

[JordaanDMC-12]

Hey all I did a search and found nothing! Even on the actual internet very vague information.

How do I go about doing this? I disconnected the battery and have all the tools but what is the process? Which ones comes out first? Is it a simple as a swap? How do I relieve the pressure on the fuel system on this car?

Please help!

[JordaanDMC-12]

ALSO**

This is my fist time doing this so I assumed that you just take the fuel lines off ect (I know, I know) I started untightneing one bolt and fuel was starting to come out so I stopped and tried to tighten it back because I wanted to make sure I was doing it right. I just read how you need to depressurize the system BEFORE you do anything.. I don't want to start the car now though because there is gas on the negative and positive terminals on the bottom fuel pump! What do I do?

When my friend changed the fuel filter on his 300E he didn't depressurize the system and he was fine wtf

[ds190]

Use clamps on the fuel lines. It's not pressure, it's gravity

[JordaanDMC-12]

Originally Posted by ds190

Use clamps on the fuel lines. It's not pressure, it's gravity

Really? so I don't have to worry about that? I can just unscrew the fuel lines?

[ds190]

Remove the gas cap first to relieve fume pressure in the tank, and then tighten it.

Yes, after you put pinch clamps on, you can loosen the lines. Otherwise, you will be taking a gasoline shower.

[JordaanDMC-12]

Originally Posted by ds190

Remove the gas cap first to relieve fume pressure in the tank, and then tighten it.

Yes, after you put pinch clamps on, you can loosen the lines. Otherwise, you will be taking a gasoline shower.

Awesome, thanks! That was really the only step I was worried about... Too bad I didn't do this on an empty tank -_- we don't have that many clamps. I think just one :S

[79Mercy]

Listen to Billybob, he is correct.

[79Mercy]

wheres it leaking from don't give up on a leak.

[JordaanDMC-12]

Originally Posted by 79Mercy

wheres it leaking from don't give up on a leak.

I know it sounds lame, especially on a leak but I don't know what else to do. As far as I can tell it's leaking from the top fuel pump, but I mean it's got new OEM washers from MB and it's as tight as it can go.. What else can I do?

the hose going from the tank to the fuel pump did start leaking but stopped after the pumps were hanging in the correct position. I didn't see fuel dripping down the hose when I tired starting it, it was just coming from the top fuel pump and dripping onto the bottom one. arrgh

[79Mercy]

show me a picture

[tinypanzer]

Yikes! Apart from learning the hard way how to work with banjo fittings, there's one thing missing from your setup. Nobody ever mentions this, and I think it's extremely important.

ALWAYS have a GOOD fire extinguisher within arms reach when working on fuel systems!!

Especially when it gets cold and the air dry, a fire that burns you badly, destroys your car and burns down your garage and house is only one itty-bitty spark away.


Now, having said all that, one thing that can make those washers leak is if the banjo pipe got torqued or dinged during the work. If the loop of the banjo isn't perfectly flush and level with the pump, the surfaces won't seal up correctly. Also, if you nicked or got plier marks on that surface, same deal. If it's just twisted a bit, you can use pliers (with leather to prevent marring) to get it straight again. If you've scarred the sealing surface, you may have to replace that part.

[JordaanDMC-12]

Here are some pictures. If you look closely you can see some form of drip mark on the banjo fittings. It doesn't look like a lot but when the car is running it drips out a lot of gas!

[JordaanDMC-12]

Originally Posted by tinypanzer

Yikes! Apart from learning the hard way how to work with banjo fittings, there's one thing missing from your setup. Nobody ever mentions this, and I think it's extremely important.

ALWAYS have a GOOD fire extinguisher within arms reach when working on fuel systems!!

Especially when it gets cold and the air dry, a fire that burns you badly, destroys your car and burns down your garage and house is only one itty-bitty spark away.


Now, having said all that, one thing that can make those washers leak is if the banjo pipe got torqued or dinged during the work. If the loop of the banjo isn't perfectly flush and level with the pump, the surfaces won't seal up correctly. Also, if you nicked or got plier marks on that surface, same deal. If it's just twisted a bit, you can use pliers (with leather to prevent marring) to get it straight again. If you've scarred the sealing surface, you may have to replace that part.

There actually was a fire extinguiser there it just wasn't in the picture. I stole it out of the 220D. I was very careful made sure nothing electrical was around and the battery was disconnected.

The washers were in bad shape and I tired reusing them which was a bad idea lol but I got OEM ones from MB and it's still leaking like I hadn't changed them. I'll check the surfaces for scarring tomorrow as I'm doing this all over again for the third time to make sure everything is in place.. Hopefully there aren't any nicks or dings in the sealing surface.

[JordaanDMC-12]

Finally after two days of trying to get these stupid pumps in and working 100% they are in, working 100%, and leak free. THANK GOODNESS!

Turns out it was leaking from where the main fuel bolt (don't know its name) screws into the actual pump. I had everything pretty tight but I didn't notice I had to tighten it there. It wasn't until my dad took the old pumps to the mechanic to see if he could give us clues and sure enough, he said that was the last step I'd missed. So I took it all apart again today, went and got more new OEM copper washers from MB to make sure there would be no leaks, rewired and put back together... I was pretty nervous about the first start but we cranked her up and no leaks. It was so amazing lol

I drove to the gas station to put more chevron in and all seems well so far. She hasn't stalled out yet but we'll see. I'm hoping the pumps were the main cause of this. Thank you all of you who helped out with this!!!!!!!!! Here is a picture of me pointing to where it needed to be tightened.

**Also, if I never had to smell or deal with gasoline again, it'll be too soon.. Gasoline is the most evil substance lol

[79Mercy]

Are you sure you installed a washer on both sides of that banjo fitting?