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Fuel tank Removal....

20K views 40 replies 15 participants last post by  81300SD 
#1 ·
Anyone have these PDF's
• 47-030 - Function of fuel tank venting
• 47-100 - Removing and installing fuel tank
• 47-120 - Removing and installing fuel gauge sending unit
• 47-200 - Function of fuel evaporation control system
• 47-300 - Checking fuel evaporation control system
 
#3 ·
Thanks Markus.
You are the man!

Markus,
You don't happen to have a picture of the back side of a Euro Gas Tank from a SEC Do you?

My tank is really different than what that schematic shows for the vent line. on mine there is one small vent line exiting the top cent of the tank and it 90]sto the rear and then 90's down behind the protective trunk wall(I haven't removed that yet) to see if there is a connection to the vent line behind that wall I do know that vent line exits through the sheet metal under the car......I think.
 
#5 ·
That looks more like it.
Thanks.
My Indy said that the Euro tanks are different than the US ones because they had this vent line and that is what my tank has. I'll take the trunk panel off and see just where that sucker goes.
 
#7 ·
Actually mine comes from the top center and loops (2 90's) down the center of the back of the tank....Don't have the foggiest idea where it goes from there...yet! I could have that one too for asll I know. But if I have to remove the tank it's not so daunting a project now, But I'm betting that it's the seals around the sender and maybe the feed, return. and vent lines that is allowing the loos of pressure. hopefully not the filler neck joint to the tank.
 
#9 ·
Yep I realize that the vent cannot be from the bottom of the tank, so this line must travel through the body sheet metal and exit where the vent line is connected. Yes I do realize that there is a feed line (big one, and a return line(small one) and the vent line. My vent line is hooked up to a vent valve and that line goes to the Charcoal canister.
What I don't know yet is IF the vent line from the top of the tank is connected to the vent line under the car via a hose connection, or if it is a single hard line to the connection under the car, (which is what I suspect).
 
#10 · (Edited)
Hey guys. I bought my SEC a couple of months ago and gas wasn't great. I mean, I thought it was partly because of the V8. But majority of it was because the fuel distributor was damaged. I replaced it with a new one a little after I got my subs (and amp, obviously) and noticed that gas became a lot better from what it used to be. But not necessarily great. The reason why I emphasize the AMP along with my subs, is because the amp is normally drilled onto the back of the backseats. That being said, I JUST found out the gas tanks on SECs are behind the backseats and not under the cars. That explains so much why gas milage isn't so great! And my car always reeks of gas whenever I load it. I never really noticed wet spots in my trunk, though. Nor does it smell after a while. Would you guys recommend getting a new tank or is this an easy fix?
 
#15 · (Edited)
............... because the amp is normally drilled onto the back of the backseats. That being said, I JUST found out the gas tanks on SECs are behind the backseats and not under the cars. That explains so much why gas milage isn't so great! And my car always reeks of gas whenever I load it. I never really noticed wet spots in my trunk, though. Nor does it smell after a while. Would you guys recommend getting a new tank or is this an easy fix?
Well, that is too bad. Sounds as though you have a very bad situation there.

As long as fuel is above where the tank has been breached, raw fuel is dribbling down the side of the tank, both when running, or when shut off & parked.
After the fuel level lowers, you're going to have a concentrate of raw fuel fumes back there. Uff.

Anyways, you'll have to drain the tank & remove before you'll know whether to repair or replace.

Earlier in this thread, Markus posted all the tank pdfs back in 2008: https://www.benzworld.org/forums/w126-s-se-sec-sel-sd/1408374-fuel-tank-removal.html#post3157176

That should get you pointed in the right direction.

MBL
 
#11 ·
You need to pop the cover panel off and inspect the tank. Did you mean you've installed amps and drilled into the rear bulkhead? Could have pierced it on that side, in which case you'd have to take the tank out and inspect, unfortunately.

It's not too bad a job though overall. You'll get very soaked in petrol when disconnecting the lines under the car.
 
#12 ·
I couldn't tell you if it pierced through the tank, actually. I was just watching a random youtube video when someone noticed (comments) that their AMP was on drilled on the back of the back seat. They went on to explain that they wouldn't buy the car (the video was a sell ad) because it probably leaks and smells. Reading that made plenty of sense to me since I have those problem. Well, the smell for sure. As for the leak, I'm not quite sure. But my gas milage isn't so hot haha.

Either way, it's worth the inspection, anyway. Luckily I'm on winter break and have almost a month to figure out if theres anything wrong with it.
 
#13 ·
Yeah worth a look. I expect they get this problem a lot, probably a lot of people assume the tank is under the car in the usual place. Same with people mounting amps in the boot/trunk, and not realising that's just a cover panel for the tank.
 
#14 ·
1991 560SEL W126 fuel tank removal

Wish I had read this thread before I had the stereo system in my car upgraded. Noticed the gas smell when i drove away. Tank was almost empty so I filled her up and odor got too strong to drive the car. So, I'm assuming I have to take the back seat out to remove the fuel tank. Any advice on whether to repair or replace? A quick search for a replacement didn't come up with any results.
Thanks,
Dan
 
#16 ·
So, I'm assuming I have to take the back seat out to remove the fuel tank. Any advice on whether to repair or replace?
If it would be me I'd request the shop who damaged it pay for the repair. Speaking of the tank, is removed through the trunk, but first you have to get under the car and disconnect the two lines to it (supply and return), then through the back of the car (after you remove the back seat) remove the level sender (which requires a bit of a special tool), then remove the trunk divider and the tank is visible (secured by 4 bolts).

The entire operation is not that easy if you know exactly what you need to do. Only after you get it out you can make a correct determination if is worth fixing it or you need to look for another one. If inside it has no rust, then it may be worth fixing it.
 
#18 ·
Hi everyone.
I am working on a similar issue. I have a bad fuel gauge sending unit, I hope, and am not sure how to get to it to replace it. I am pretty sure I have to remove the power rear bench seat and seat back to gain access to the bad sending unit, but I'm not sure how to get the seat out. Anyone have any suggestions?

Thanks guys!
 
#24 ·
The fuel tank sender is in the top of the tank, under the first aid kit. Shouldn't have to do anything with the seats.

I can measure that big "bolt" if you need but it's about 1 3/8". I tried to get one out with a 1/2" ratchet, no go. Added a pipe to it, no go. Grabbed my 1/2" impact gun and it popped right out. Aluminum tank sender top into a steel tank = galvanic corrosion.
 
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#26 ·
Ya, I took out the first aid kit box, no small feat as there aren't any screws holding it in, but rather it's just sitting in there with the parcel shelf liner and the screw for the latch holding it in. There's just enough room to slide the box side to side, but not enough to actually get it out. Anyway, I finally got it out, and could just barely see the top of the sender unit, but there was no way to reach it without removing the seat and seat back. I used a tool I got on MercedesSource specifically for that sender and the in-tank filter on the bottom of the tank at the hose feeding the fuel pump. Had to get a little tough with it, but it worked like a champ and the sender came right out.
 
#27 ·
I checked on the EPC and below are the part numbers for a 500SEL gas tank, for a 560SEL, and a 560SEC. If you need one, looks like my SEC tank will fit. I've had a motorcycle tank successfully cleaned out and internally epoxy coated. Now you have options.

500SEL A1264704001
560SEL A1264704001
560SEC A1264704001
 
#29 ·
mramay

Thanks for your research. I always appreciate having a few options available as usually my "Plan A" blows up in my face. I don't even want to tell you how many "Plans" I had to go through to get my sprinkler system just right. :)

Just out of curiosity, how much do you need for your SEC tank?

Thanks again!

Jason
 
#33 ·
Just took my tank out to repair hole made by stereo installer. It's not too bad. Question for accessing the sending unit: That's a large socket (if you don't have the tool) 1&15/16ths i think is what we used to remove sending unit and filer for examination. Is there room for that tool after you take the seat out? My tank and all were incredibly clean, fortunately. Good luck with your repairs.
 
#37 ·
Hey Herk Driver.
Yes, it's probably the largest socket I've ever had to use on anything. I actually got the tool from MercedesSource that they made specifically for that sending unit and the in-tank filter screen on the bottom. I was a little worried about getting a tool that I would only use a couple times, but I gotta say it worked beautifully.
Yes, once you get the seat bottom, and seat back out of the car, there is room for the tool, or socket if that's what you are using, but you have to take out the two bolts that hold the seat frame to the car, then the whole thing kinda pivots up and back just enough to access the sending unit.
Sorry to hear about your stereo installation issues, but glad the hole is repairable for you. And glad your tank is in good shape otherwise.

Good luck with your project!

MBZ ROX!

Jason
 
#35 ·
For $100, it's a deal.

But unless there is significant thinning of the tank by rust, take a pass on the coating.

At that price, whatever they are using is so cheap that you probably would not want it anyway.




No warranties express or implied.

Your mileage may vary.

Not intended to replace the advice of a physician.
 
#36 ·
Ya, I'm a bit weary of the quality I'll get for $100, but in their defense I didn't tell them it was a 25 gallon tank. They do a lot of motorcycle tanks, so maybe the price is low because the guy I talked to thought I have a tiny tank. We'll see what they say when I bring it over to them. Hopefully I'll be able to drain and remove mine tonight and run it over the first of the week.
I'll keep you guys updated.

Thanks!

Jason
 
#39 ·
Hi guys.
Thought I would give a quick update on my project. Got the tank out and over to be cleaned and coated. Turns out they can't coat these tanks because there are some plastic bits and parts inside the tank which will get ruined by the coating. I had them clean it out really well and have it installed and ready to fill as soon as my new fuel screen gets here. The good news is that I turned on the ignition and I now have a "low fuel" light. :)
I figured since everything was drained and taken apart I would put in a new fuel pump, filter, screen, sending unit, vent check valve and hoses, supply hose from the tank to the pump, hose from the filter to the fuel line and a new return hose from the return line to the tank. She's going to look amazing! Cant wait to put in the new screen, install the pump assembly and fire her up...

Thanks for all the advice! I really appreciate it!

Jason
 
#40 ·
Hi guys.
I figured since everything was drained and taken apart I would put in a new fuel pump, filter, screen, sending unit, vent check valve and hoses, supply hose from the tank to the pump, hose from the filter to the fuel line and a new return hose from the return line to the tank. She's going to look amazing! Cant wait to put in the new screen, install the pump assembly and fire her up...

Thanks for all the advice! I really appreciate it!

Jason
Yeah, good call, you'd be nutz if having it down to nothing and not replace everything fuel related back/down/under there because (if "luck" like mine) the one thing that wasn't replaced would be where the leaks would come from and you'd have to tear it all back down AGAIN to fix the "cut corner"

Now, and for a while, I subscribe to the "while yer in dere, fiss it, yeah dat too" :grin program of Mercedes maintenance/repair
 
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