How to replace fuel pumps on m103 - PeachParts Mercedes-Benz Forum

JordaanDMC-12 · #1 11-15-2009, 12:38 PM

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 · #2 11-15-2009, 01:07 PM

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 · #3 11-15-2009, 01:11 PM

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

JordaanDMC-12 · #4 11-15-2009, 01:15 PM

Quote:

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 · #5 11-15-2009, 01:23 PM

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 · #6 11-15-2009, 01:26 PM

Quote:

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

JordaanDMC-12 · #7 11-15-2009, 02:46 PM

Someone please help, I have no idea what just happened and I don't know if I'm doing this right.

I tried taking off the fuel lines and one of them broke. The line from one of the pumps to the furl filter. This is such a nightmare.... What did I do and where do you unscrew them from? Did I totally mess this up?????? lord have mercy lol

This is what i'm dealing with at the moment.

Billybob · #8 11-15-2009, 03:32 PM

Looks like because you did not use a second wrench to "back-up" the fitting you where trying to break free you ended up twisting the entire part an broke the steel line where it connects at the banjo fitting. There is a fitting which threads into the fuel pump and there is a banjo connection with its own nut which connects to that. You should have used a wrench on the fitting where it threads into the pump to hold it from turning then another wrench on the nut securing the banjo fitting to crack that nut free.

Now you need a replacement line, that about $30 last I saw. You will also need replacement crush washers for each side of all the banjo fittings in order to prevent leaks when you re-assemble everything. A small dab of grease on the electrical connections to each of the fuel pumps will be much appreciated by the next person to fool with them, also replace the rubber boots on the electrical connections if they are torn or damaged. When putting everything back together grease the screw which tensions the bracket holding the two pumps together, it’s small and Philip’s head so it’s easy for it to be a pain to remove if it gets any rust.

Get everything together loosely and in place and then give the fittings their final tightening torque that way there is no tension binding between the parts.

79Mercy · #9 11-15-2009, 03:37 PM

Listen to Billybob, he is correct.

JordaanDMC-12 · #10 11-15-2009, 03:47 PM

Quote:

Originally Posted by Billybob

Looks like because you did not use a second wrench to "back-up" the fitting you where trying to break free you ended up twisting the entire part an broke the steel line where it connects at the banjo fitting. There is a fitting which threads into the fuel pump and there is a banjo connection with its own nut which connects to that. You should have used a wrench on the fitting where it threads into the pump to hold it from turning then another wrench on the nut securing the banjo fitting to crack that nut free.

Now you need a replacement line, that about $30 last I saw. You will also need replacement crush washers for each side of all the banjo fittings in order to prevent leaks when you re-assemble everything. A small dab of grease on the electrical connections to each of the fuel pumps will be much appreciated by the next person to fool with them, also replace the rubber boots on the electrical connections if they are torn or damaged. When putting everything back together grease the screw which tensions the bracket holding the two pumps together, it’s small and Philip’s head so it’s easy for it to be a pain to remove if it gets any rust.

Get everything together loosely and in place and then give the fittings their final tightening torque that way there is no tension binding between the parts.

Thanks billbob! I'm now on my way to go get another fuel line... ugh a mistake i'll never make again that's for damn sure lol

Billybob · #11 11-15-2009, 04:37 PM

Quote:

Originally Posted by JordaanDMC-12

Thanks billbob! I'm now on my way to go get another fuel line... ugh a mistake i'll never make again that's for damn sure lol

I'd be suprised if it's a stocked item! World Pac does carry it I'm almost certain, if not its a dealer part! Don't forget the crush washers!

JordaanDMC-12 · #12 11-16-2009, 02:59 PM

Well I got up at 6:00 this morning to finish everything up and I put it all back together at 11:30 and started it up and she ran! The most beautiful sound in the world atm!!!

Just (hopefully) one last problem. I reused the old copper washers from the other pumps and put them on the working ones

It's now leaking....

So i'm off to get some washers and be done with it!!!!

JordaanDMC-12 · #13 11-16-2009, 07:25 PM

I hate to say it but I give up lol

After both fuel pumps got brand new OEM copper washers from Mercedes-Benz of Palm Springs and the darn thing is still leaking pretty good when there is pressure in the system. I have no idea why... I think I might just take it to the mechanic my dad has been saying we take it to since the start. Guess it's time to admit defeat by a fuel pump job.....damn

79Mercy · #14 11-16-2009, 07:28 PM

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

JordaanDMC-12 · #15 11-16-2009, 07:34 PM

Quote:

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