There are acids that will remove the rust and not harm plastic. Your tank is junk.
I think you would be better off getting a good used tank. Check the EPC. I think the 380 uses the same tank.

 

wschnitt,I to have fueltank problems.I have a 1985 380 and after looking at my fueltank I new it was shot so I deceied to cut the top off mine to see how fuel is dispersed thru the fuel system,as you can see in the pics the return line acts like a squirt gun in the swerrl chamber.if the target hole in the bottom of the swirell tank is pluged fuel has to flow over the top of swerrl can for fuel pump to get any fuel wich takes at least half tank to make this happen. As you can see in the pics.the po tryed to fix the tank with a liner that was a fail from the getgo as he did not understand whats going on in there.as you can se in the pic I cut the return line to show the liner pluged the return line ,and the little pieces of liner came out of the return line that I cut off in 2pic,as you can see no way that liner is going to stick to that swirell tank,thus pluging the strainer in bottom of tank. I have more pic if you need them wschnitt...Cheers, scott

 

Which is why I am not a fan of trying to "line" or coat a used tank...

 

first off Guys please excuse my typing skills. well i took a few more pics of the tank hopeing this might help folks with fuel issues. as you can see in the pics there is no way fuel can get to the suctionscreen if that little hole is plugged in the bottom of the swirrle can. like i said ,the little squirt gun at the end of the returnline might not have enough pressure to blow out any crud thats in there,wich i think can cause a lot of problems(wont run after half tank,runs good for a few min.,on and on)as you can see in the pics i think its possable to cure a lot of issues by takeing out the fuel sender and putting a air nosel at that little hole in the bottom of the swirrel can and blowing out all the crud. btw, if you lift the softop in the back you can see the big plug in the bottom of the softop house and can acess that fuelsender from there and not have to pull tank....Cheers,Scott

 

and

 

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Thanks for the additional pics rwa.

 

yup

 

Thanks for those revealing pics, bud. At long last I think I understand why my W123 would never maintain autobahn speeds with a half-tank of gas.

Good road,

 

So red is the tank feed to the swirll pot and blue is the return line? I also only see one small hole at the bottom of the swirll pot so do both the tank supply and return line "T" into that hole? If so depending where the blockage is blowing air into the return may have no affect at all if the blockage is on the tank side of the union.

 

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I thought that blue pipe was the end of the air nozzle...

 

petesmqa,there is no union there, the red line you have circled is the returnline i cut off and the blue circle is the blownosel to open the small orfice on bottom of swirrel tank. as you can see in pics that liner shit can even get into the return line that you circled in red.....hears a pic of blowgun in the tank

 

Got it, Thanks.

 

So how does a fuel tank get into this condition? I'm guessing long term storage with a near-empty or empty tank.

That W123 I owned in Germany that I'm guessing had a rusty tank had been stored in a dry garage for at least a year before I bought it. But the body was pretty much rust free for a 20-year old Germany-driven car. I'd like to know how to avoid this happening to my R107 that isn't driven 4-5 months out of the year.

Do those gas additives really disperse any water droplets that condense and settle to the bottom of the tank? Which are better, the alcohol-based ones (like HEET) or petroleum-based variety (like STP, Techron, etc.)?

Good road,

 

Which are better, the alcohol-based ones (like HEET) or petroleum-based variety (like STP, Techron, etc.)?

When I lived in the midwest I had a 1976 Corvette for a few years. In the winter I used Sta-Bil in the gas tank. It always started in the spring.

Sta-Bil Fuel Stabilizer

 

When I cleaned out the tank from one of the 450's, I submerged it in acid for 5 days...then took a high-pressure water hose to it. Chunks of crap were coming off. Then I took a wire hanger and fed it through the tank lines. The lines were full of gunk.

 

Fuel starvation - two different 107s

So I read all of this with great interest, since I just helped my dad purchase a very nice looking (and at the test drive time, running) 87 560SL.

When I went to bring the car back from Savannah to Hilton Head in the middle of TS Andrea last Thursday (6/6/2013) all went well until I got to downtown Savannah and the car just petered out. Managed to finally get it started and literally drove straight back to SC without stopping or slowing down. Not many folks on the road in a tropical storm, so I got lucky.

Without getting into details, after reading all this, and then coming to the conclusion that my own 380SL only starts stumbling when the fuel drops below 1/2 tank, I eventually found these threads.

Totally makes sense...

I'm thinking both my 380 and my dad's 560SL have tank/filter issues. I'm going to ask my mechanic Frieder to look at this first with my dad's car once it's towed to his shop. You guys may have save me many diagnostic dollars!

Thanks!
Anton on the Island

 

I find you forum members fantastic! I recently bought a 1985 Mercedes 380SL with 107K original miles on it. The car has been sitting unused for 10 plus years. You can well imagine that my car has some of the same problems that all of you have been discussing on this thread. I have really been enlightened through your discussions. Thanks a million! I will begin with the removal of my gas tank tomorrow. If I find the exercise and the results worth talking about, I will post some of my efforts on here. Thanks for all of the information that this knowledgeable group has provided. It's greatly appreciated!