turbo97se

I decided to replace a gasket I thought was giving trouble. I can now confirm it is not the gasket. Image below are the gaskets. The black one is the original one and the green one is the replacement part. I had thought that the gasket was leaking so I replaced it. Either way you are going to have to remove the sender so here are some steps as to how to do it.



Below is a picture of the fuel sender. It is underneath the back seat behind the driver's side. Actually there are TWO, one on the driver's side and one on the passenger's side. Only my driver's side one was leaking! So I am only showing that



Step 1. Disconnect battery in trunk
Step 2. Remove rear seat - there are two indentations that need to be pushed in to release the back seat - I didn't take pics.

Step 3. Disconnect the plugs to the sender and fuel pump
Step 4. Remove the black fuel line - be VERY careful here not to pull too hard on the fuel line since it is rather weak plastic it flexes very easily and could break. I took the liberty of replacing the hose and added some good stainless clamps.
Step 5. Turn the black ring counter clockwise to release the sender and pump.
Step 6. Ease the fuel sender up slowly and carefully. You have to wiggle it up. Do not pull too hard, there are hoses attached inside the tank

Below is a picture of the sender out of the tank:



I did not know this when I took the picture but the leak is occuring where the line is shown (above)

Below is a picture of my finger pointing at it from the top view ... after I had reinstalled it and topped up my fuel tank .... grrrrr!



The place it is leaking from is where the fuel pump sits. I would see fuel pouring down from the gap the line points to.

Let me finish off my "DIY" here

Step 7. Pull the old gasket out by sliding it over the fuel sender so you do not have to disconnect the tubes inside the tank.
Step 8. use mineral oil to lube up the new gasket and slide over the fuel sender and place on the tank lip.
Step 9. slide the sender back in carefully so as not to push the gasket into the tank.
Step 10. Put the black ring back on (clockwise to tighten).
Step 11. Use brake clean as lubricant to slide the fuel hose back on (remember to put hose clamps on first). Slide on quickly before the brake clean dries.
Step 12. tighten clamps on fuel hose - be VERY careful here since the tubes are made from plastic and VERY easy to crack! just tighten to where the clamps don't rotate or slde and then snug down a little. tighten until the hose does not rotate easily.
Step 13. Hook up battery
Step 14. Start car and check for leaks before replacing everything.

Step 15. Fill up tank
Step 16. Get really angry when it leaks out of the fuel pump cap!!

So ... I am not done yet but at least I know where the fuel is leaking from precisely. I need to take a closer look at that cap to see how it is held on there.

That's all for now .. I'll upload more pics and info as I find out more. If any one else has more info to share, please do!

EDIT: I think the driver's side may only have a sender and not a pump ... maybe someone else can verify this. I did not spend a whole lot of time looking at the sender. In any case it is leaking from that cap ... whatever it is!

Yacht Master

Good job! Thanks for taking steps to help us all out, When mine was recalled the dealer put a sleeve in the fuel barb. The claim at the time was that the factory hose clamps would crush/crack the fuel barb (part the hose goes on) and cause a leak.
The material the pump/sender is made of looks like nylon and I think our ethanol enriched gasoline may be causing part of this problem.

Turbo97, your leak looks like it is on a "glued" seam, is that the case?

turbo97se

Sure thing! I am an engineer and don't like to just have people replace parts without fully understanding why. Just replacing the sender will fix this issue but I want to know why cos it will likely happen again!

I showed a buddy of mine real quick and we think it is supposed to be a glued seam (as you said) - not sure yet. Going to try to plastic weld this and see what happens. Now I need to drain my fuel tank since it is pouring out of there! Grr I'll probably pull the sender again tomorrow.

The fuel barb would be easy to crack, it is very thin ... I don't like the design at all. Both sides of the fuel hose go to plastic barbs that are really very thin. You need to be really careful when tightening those clamps.

shardul

iTrader: (1)

nice DIY

turbo97se

I tried to pull the sender out yesterday, but you need to pull the fuel pump assembly on the passenger's side (right side) first. The hoses have disconnects on that side and are crimped on to the sender on the left side. After looking at the right side, I may want to replace both sides ... I'll have to see. There are signs of cracking on that side too. I would like to urge everyone to please check under your rear seat for these issues. On the left side I was shocked at the big fuel puddle that it left when I topped up my tank. My car is a 2005 .. I don't regard it as being very old. Mine supposedly had the recall done before. Please check yours ... just a safety thing. It only takes 10 minutes to check if that.

dansamg

Where you able to pull the cap?
mine is leaking from the same place. I dont want to start an expensive exploration out.

Thanks

03RSTT

Nice work. I have both the assemblies that came out of our E55 this past fall. If you need any pics or have detailed questions LMK. We replaced both sides and saved the old ones. (12,000 miles old after the recall)

The driver side assembly has the fuel pressure regulator in the housing. Thus, there is a a major source of pressure under that side. If this cap is exposed to that pressure....could be a source of many problems.

moosejaw

OP
Did you get the evap error code?
I too replaced the gasket but the check engine light kept on coming back after filling up,
I plan on replacing this, however in the last two months i decided not to fill up the tank and the error code doesnt come back.
BTW How much was the new part?

AMGPilot

You're probably getting the evap error because the evap valve is cracked. Problem is the fuel tank needs to be replaced....

The Evap Valve which is located on the saddle and goes to a 1" vent line cracks and leaks. When it leaks the fuel will flow down to the pump/sender basket and pool on the pump or sender.

The ONLY way to see the evap valve leak is to drop the fuel tank (After you drop the exhaust and drive shaft)

turbo97se

I pulled the sender out completely today. To pull the sender you need to disconnect all the piping from the pump side (right side of the car under rear seat). I will post some pics here but didn't take photos of everything. I will take better pics when I reassemble.

Here is a picture of the pump side (right side of car) You can see there is a major crack forming ... . There is an Airtex replacement for this side that sells for about $300 E8572M ($350 from Rockauto). There is no Airtex replacement that I can find for the sender part (left side)



Below is the fuel pump side. Need to disconnect 4 pipes and 1 harness connector. There are two pumps in the tank which is nice. You disconnect the pressurized lines by pulling the locking clips on each pump (I only show one here). Then pull the pump assembly to the right side of the car and release the Y-portion that feeds to the other side. I will take a picture to show this. The whole thing is a little bit of a spaghetti because of the dual pumps. I imagine the non E55s are probably single pumps not dual. Note the un-insuated terminals (browns are grounds, Reds are power) Never heard of molding them into a single plug so no way for them to come off and touch? - THANKS MERCEDES!

turbo97se

Below is a picture of a fuel pump assembly - borrowed this from Airtex. You can ignore my rightmost comment in the previous picture. A Y-pipe connects the two pumps. You can disconnect at the end of the Y (top right with red button on the picture below) instead of at each assembly.




Just noticed the sizes of the pics ... I'll fix those later .. more coming soon Annotating pics and taking more....

AMGPilot

That's the way EVERY car manufacture does it, nothing wrong with the way Mercedes does it. And as a point of reference liquid gas will not burn, it's when it's in vapor form or atomized into microdrops that it burns. You can put out a match in gasoline.

turbo97se

Hmm ... I haven't worked a lot on German car gas tanks before so may be my experience is limited. I know for sure Japanese cars use a single molded connector so the parts cannot possibly touch.

I know that liquid gasoline does not burn on its own .. need oxygen in there too. However, these connectors are not always completely submersed in gasoline. They sit in air and gasoline vapor when you are at anywhere below 3/4 of a tank of fuel.

Interesting that Mercedes were careful enough to ground all the metal components in the fuel tank maybe to avoid electrostatic discharge, but would allow a power wire to be naked in gasoline vapor and air.

turbo97se

Hmm ... I wonder why my original post cannot be edited?

At step 4, I would recommend cutting the fuel line off and replacing it rather than risk cracking the sender or other end. You can get the fuel line from local parts store. I got mine for free since it was an offcut.

Step 6. I would like to recommend that people wear grounding straps (especially in low humidity environments). Strip some wire and connect to body chassis, the other end, tie to your ankle. Gas fumes are highly flammable so want to avoid discharging a spark. It's been rather dry the last couple of days and I have been discharging quite a bit. Have a bucket of water/hose and damp cloths handy as well as fire extinguisher!

Other thing is a disclaimer that I cannot be responsible for any damage for work you do on your own vehicle!

I am going to replace the entire unit at this point - there are hairline cracks in the plastic webbing that cannot be plastic welded.

Some pics of the cracks .. and yes they are cracks and not just dirt!:



More cracks:

turbo97se

Here is a picture of the sender with its spaghetti pipes. Since I determined it was to be replaced, I decided to take it apart.

The top of the sender twists off




description of the piping:



Below are pics of the sender internals ... OK I was bored! LOL ...

The Sender has

1. Fuel pressure regulator on the bottom held in by a c-clip
2. Pressure sensor (The part that is leaking)
3. The fuel level sending unit
4. Filter

Not sure why they made this so complex! Lexus IS300s have a saddlebag design fuel tank too but the pump, sender and regulator are all in one unit. Granted it is single pump but there is plenty of space in there to put a second pump!

dvdt

This is a great post! So the filter is on the sender assembly and its pretty much impossible to buy the filter separately. FUN.

03RSTT

It was good to pull this thread up. I dont think some of the new guys have looked at the extensive photo list that the op listed. NHTSA also needs to look at these photos because only an engineer can go into this sort of detail.

And knowing that the leaks are from cracks developing in the plastic used to house these components there is no way on this earth to ever fix this situation short of gutting the rats nest of wires and pumps and throwing it all away.

The design is the worst. Audi simply installed a fuel filter outside the tank and included a fuel pressure regulator and short return line back to the tank to comply with EPA fuel returnless guidelines. Audi does not have this rats nest of garbage in the fuel tanks. Just a lift pump for volume and then a outside pump for pressure.

WHTEVO

I also agree this is a good thread. I wonder if the replacement unit fixed the OP's issue?

Aaron

BBBSS

Wonder if a $300 airtex sending unit would solve some of our problems? Seems the plastic chosen is of poor quality for the application at hand. That's probably a manufacturing issue but MB should have had some say in the materials chosen. Perhaps they chose the cheaper of a few options and here we are? Does ethanol make this plastic brittle and prone to cracking?

Be interesting to see one of these soaked in pure ethanol for a while.

dvdt

I did some googling at it seems like Airtex makes a ton of replacement pumps for various manufacturers and the quality is hit or miss...

If i ever arrive at this issue i'll probably just try and get a discounted genuine MB pump.

efiftyfizzle

I can't believe there are all these aftermarket pulleys, heat exchangers, etc. mods to make your car go fast, but not one attempt at replacing this junk MB has left us with which deals with reliability of our cars. Do we value speed / adrenaline more than reliability? lol

Forrest Gump 9

Thank for pulling this thread up.

Can I fill the crack areas up with JB weld?

Hulk

a fab guy i know and also bruce from TTM , said we should fill the senders with epoxy, if I understood correctly

03RSTT

I might say a coating of epoxy over the entire surface might help but remember that if a crack develops its under pressure and starts to spray out. Unless the epoxy has bite into the plastic it will just creep out under or between the epoxy and housing anyways.

I will also say this. GregMB if you are reading this thread and are still in contact with NHTSA...some of these pictures should demonstrate that a serious flaw or defect is located in the actual plastic material that these sending units are made of. My MB dealer has said they replace these sending units daily and the same cracks are developing in the housing that were developing in the fuel nipple port to cause the recall in the first place.

How friggin hard is it to just demand that the supplier change the plastic to a more crack resistant and heat resistant form.

Recall these damn cars again and make a real fix.

Stupid rats nest of lines and emission equipment. Throw it all in the trash bin and install a simple lift pump, pressure pump, fuel pressure regulator on the engine and return line. No more pressure in the gas tank and no more leaks.

Hulk

i thick amount of epoxy should save it even if the unit cracks..in theory