W124 fuel tank removal tips - PeachParts Mercedes-Benz Forum

ps2cho · #1 07-03-2011, 11:32 PM

I am going to need to pull the fuel tank out and take it to a shop to be cleaned and such....

I tried to tackle it about 2 months ago (albeit in an apt complex which made it difficult -- I am in a house now so gonna try again).

...I had not disconnected the main fuel line underneath, but was hoping if I could lift the fuel tank UP I could get at the line from inside the trunk. Can that not be done? I couldn't even get the damn tank to move an inch at all. I drained all the gas too, so it wasn't the weight.

Any tips or tricks on how to get it out successfully?

I got a new tank filter on its way to me. I'll just have the shop clean and do whatever they do to make sure its 100% rust-free. From there I can start replacing pumps/accumulator/fuel pressure reg one by one until I can get the 260E running properly again.

Ferdman · #2 07-04-2011, 06:15 AM

ps2cho, according to the Haynes Service Manual:

1) Depressurize the fuel system and disconnect the battery.

2) Label and disconnect the supply, return and vent hoses.

3) Unhook the rear section of the exhaust system from its mountings and temporarily support it on wood blocks to avoid straining the joints.

4) Disconnect the wiring from the fuel sender guage at the connector.

5) Support the underside of the fuel tank using a trolley jack and a block of wood to prevent damage.

6) Unscrew the nuts and remove the support bar from the rear of the fuel tank. Similarly, unscrew the nuts from the mounting brackets at the front of the fuel tank. Recover the washers and bushings.

7) Lower the fuel tank away from the underside of the vehicle, making sure that nothing remains connected to it. Revover the padding strips if they are loose.

8) Unscrew and remove the fuel strainer from the tank, recovering the O-ring seal.

Reinstall the fuel tank by reversing the removal procedure, noting the following points:
a) Use new self-locking nuts on the fuel tank mountings.
b) Ensure the padding strips are refit correctly.
c) Ensure the sender unit wiring plug is securely reconnected.
d) Test drive the vehicle and then check around the area of all disturbed components for signs of fuel leakage.

ps2cho · #3 07-04-2011, 11:29 AM

Thanks...this is for sedan, not wagon though

ps2cho · #4 07-06-2011, 01:44 PM

Got it.....

Looks like it wasn't moving due to the headrests which lean down slightly.

Looks like I'm gonna need a big socket or wrench to get the strainer out....Don't have anything big enough right now.

ps2cho · #5 07-06-2011, 04:11 PM

Managed to get the fuel level sender off using the wrench -- I peeked inside and I see some crud, but it looks OK. I couldn't get the strainer out though due to it being further recessed in the tank.

I do see some rust, but its around the strainer in that area? It looks like its blocked off, almost a separate chamber? Why would that section have rust, but the rest of the tank look perfect?

I wish I could get a photo, but the flash and camera lens can't get the shot with the size of the hole...

ps2cho · #6 07-06-2011, 06:35 PM

Found a sears (although an hour away) that carried a 1-13/16th in socket in 3/4 drive....Got a 3/4in -> 1/2in adapter at Harbor Freight and and old strainer is out.

Doesn't look bad either....

I'm thinking this may be something I don't have to take to a shop to fix.

Whats the best acid product to clean the tank with? The walls look perfect, its just the section around the strainer that has some "slight" rust. Is that section something to do with hard cornering and keeping fuel available?

After clean, any sealer or anything?

I got a few photos to come out ok....You can see not bad at all inside!

So I'm guessing its gonna be new fuel pumps and possibly FPR and/or accumulator. I may junkyard grab those 2 though since they are expensive.

EDIT: Just got some better shots.

I don't see ANY rust at all

I wonder what the hell happened then? Maybe a bad batch of gas nuked the fuel system?
I saw the particles though, so SOMETHING was running through the system!

Hmmm....

ps2cho · #7 07-06-2011, 08:03 PM

Alright, so let's get back to the drawing board

Fuel Tank + Strainer --- GOOD.
Fuel Pressure --- GOOD.
Fuel Injector Spray Pattern --- GOOD.
Fuel Pump Volume --- INADEQUATE.
---> FSM states:

If delivery is less than 1L in 40sec test following points:

a) Check fuel strainer for blockage ---> GOOD.
b) Fuel Pump voltage is at least 11.5v
c) Check for fuel line restrictions (pinched lines)
d)Pinch of leak line between fuel accumulator and intake damper. Check Delivery and if its good, replace accumulator
e) Replace fuel filter ---> GOOD.

I'll get the fuel tank shaken and stirred to get rid of those "bits" it has at the bottom then put it back in the car and get some gas back in it. From there I'll go through the list....

Question 1: Anyone understand the charcoal filter part of the fuel system? I have no idea about anything related to it. Is there anything that side I should be checking at all?
Question 2: What is this intake damper in regards to accumulator?

ps2cho · #8 07-09-2011, 02:04 PM

I've decided to first replace ALL rubber hoses in the fuel system.

I checked the EPC, but I cannot seem to find a parts diagram that lists all the hoses from the fuel tank to pump? Also the rubber hose that goes from the fuel pressure aka return line...

Anybody know where I can find part #'s?

sptt · #9 07-09-2011, 10:08 PM

Have you tried Parts Geek dot com ?

timc · #10 07-10-2011, 12:18 AM

i bought some of them from this site, but try also Germanauto and M%RCEDE$$OURCE.

KJZ78701 · #11 12-20-2017, 02:05 PM

What ended up being the problem here?

Since installing a new fuel pump with the new motor last summer, I experienced fuel starvation when the tank got down to 1/4 or less. This happened twice (i.e. the car stalled) but with two gallons in a jug in the trunk I just filled and off I went to the gas station. We went months without letting the tank go under 1/4 and had no issues. Just last week, we didn't get to the gas station in time and the motor stalled again after, oddly, several miles of hesitation. There was no hesitation the first couple of times. It ran perfectly and then stalled when I took my foot off the gas to make a turn. Now, after filling the tank completely, the motor starves for fuel around 2000 RPM. So, it starts and idles, but effectively cannot be driven.

Sadly, I am away from the shop so checking fuel pressure is not a DIY option. I will check fuel volume at the pumps here in the next couple hours, but was hoping someone else might give me some additional places to look.

p.s. When I checked the strainer from inside the tank a couple months ago (just after the first starvation at low fuel level episode) with a borescope, it looked nearly new. Anyone actually checked flow rates through and old, but clean looking strainer to see if they get microscopically clogged?

p.p.s. My tank has a different looking catch can around the strainer than ps2cho's. It seems my return line (inside the fuel tank) should dump back into this catch can, but the borescope indicated that my return line is split just before the catch can, so returned fuel is not going back exactly as it should. Anyone have a fix, short of replacing the entire tank?

Ferdman · #12 12-21-2017, 06:30 AM

KJZ78701, consider using some Techron to clean the fuel system. Even though the fuel tank appears clean, there may a slight blockage in the fuel lines which reduces fuel flow. When was the last time you replaced the fuel filter? The service manual recommends fuel filter replacement every 60,000 miles.

280EZRider · #13 12-21-2017, 09:22 PM

[Question 1: Anyone understand the charcoal filter part of the fuel system? I have no idea about anything related to it. Is there anything that side I should be checking at all?
Question 2: What is this intake damper in regards to accumulator?

[/QUOTE]

If by "charcoal filter" you are referring to the charcoal cannister in the engine bay, this is part of the emissions system and stores fuel vapors after the engine is turned off, after which they are sucked into the engine for combustion once the engine runs again. This would have nothing to do with inefficient fuel pressure from the tank.