Fuel tank questions

[andre]

So I think I have a flower pot issue in my 71’ 280sl.  Although sometimes it seems to happen with more than ½ a tank of fuel.


I’ve had what has feels like a fuel delivery issue for a while.  I replaced the fuel pump and the stumbling went away for a period of time.  Then it came back, my thinking is it may have gone away do to the new fuel pump (slightly hotter) and the in pump filter being new ( less restrictive).  I don’t drive the car often about 3K in the last 7 years (61K total miles).  First thing I thought was to check the flow at the fuel return line from the engine (at the tank).  Slow, over a minute to fill an empty beer bottle.  After draining the tank I blew through the return and supply lines, clear passage.  I started to remove the tank and this was more difficult that so I removed the large drain plug and the sending unit and look through the inspection hole (sending unit hole).  The screen had a little grit in it nothing major around the inside of hole there was more grit.   Next step, check the flower pot flow out so I replaced the plug and started to fill the tank with water well there was just a trickle out the supply line ( I ran out of empty beer bottles because the kids took them to the recycle center).  Anyway, how fast should the flower pot fill up, when fuel is under the top edge?   Should it drain the tank completely dry I still have a little ½ - ¾ inch of water standing in the tank that I have to get out?  I also had the occasional “burpâ€? which I suspect would create air bubbles that could collect in the filter canister and displace fuel? Where are the holes that allow the flower pot to fill and how large are they?  Dan mentions that you can dig around in the inspection hole and “clearâ€? then/it.  What should the fuel pressure and volume be like at the return hose at the tank?  I’m thinking the filter in the fuel pump might have some “stuffâ€? also restricting flow and volume.  I read and reread the tank tour and looked at the pics very close and can’t see where it fills.

Also, is there a trick to removing the gas tank?  Or must the fuel pump and the exhaust be dropped?  I pulled the fuel pump just figured I would ask before lowering the exhaust.

André

[glennard]

Remember: If there's a dirty Shroud of Fuelin,
             There will be no Pagoda Tourin!

     As I remember my fuel tank problem---
  The Shroud of Fuelin holds more than a quart, less than a gallon or say 10 miles or so of gasoline, plus a filter.    Gas enters an empty tank and rises to fill the volume of the greater tank and the Shroud of Fuelin- if the openings in the bottom of the Shroud are free of rust and crud.  At about 3/4 full the gasoline can spill over the top of the Shroud.
     Starting the car circulates gas from the bottom inside of the Shroud, to the engine, and back to the inside of the Shroud.  Once the tank level falls below the top of the Shroud, gas must come into the Shroud via the openings in the bottom of the Shroud.  If the rusty crud drops the flow rate below 4 gph, the electric fuel pump gets starved when the Shroud goes dry.   Tank could still be 3/4 full.

    My tank had about 2 quarts of crud outside the Shroud in the bottom of the greater fuel tank blocking flow thru the openings into the Shroud.   I think I drained the tank, turned the car upside down, and flushed and vacuumed the tank.

[glennard]

Remember:  If there's a dirty Shroud of Fuelin,
                  There will be no Pagoda Tourin!

My memory of the problem goes like this--  The Shroud of Fuelin in the center bottom of the greater tank holds more than a quart and less than a gallon(10 minutes or so driving time), plus the in Shroud filter.  The electric fuel pump takes suction from inside the Shroud, pumps to the engine, and the excess returns to inside the Shroud.  
     Filling the greater fuel tank also fills the Shroud via openings in the bottom or, at about 3/4 tank, gas spills over the top of the Shroud and into it.  
     When the engine is running and the tank is less than 3/4 full, the engine burns gas and empties the Shroud in the 10 minutes or so unless new fuel flows in thru the openings in the Shroud's bottom.
     My tank had about 2 quarts of cruddy rust in the bottom of the greater tank outside the Shroud blocking the flow into it.  I think I drained the tank, turned the car upside down, and flushed and vacuumed it.

[andre]

So the holes are near bottom of the "pot"?

 Does the fuel flow under the pot to fill? I cleaned and vacuumed the tank and got about a table spoon of junk out.  I'm going to give her a second round tonight if I get a chance.

"If the rusty crud drops the flow rate below 4 gph, the electric fuel pump gets starved when the Shroud goes dry" ? So the additional fuel that one would burn is from the return line?  I believe I'm above the 4gph but that would be pretty easy to test from the supply line.  By filling the tank below the top of the pot and checking my 2 gal bucket every 15 mins.

[glennard]

Andre, The electric pump should do 40-80 gpm at 15-20 psi at the injection pump suction.  This is 10 times the fuel burn of 4 gph at 60 mph and 15 mpg.  If gas flow is restricted by crud between the greater tank and the Shroud, the Shroud is soon emptied and suction is lost(flow) is lost.

[Naj ✝︎]

Andre,

This may answer your 'flower pot' question:
http://www.sl113.org/forums/uploaded/ja17/20047104938_illate%20tank,%20flower%20pot%20illus..JPG

Also, have a look at the tank tour:
http://index.php?topic=1712&whichpage=1
 

quote:I think I drained the tank, turned the car upside down, and flushed and vacuumed it.

I trust this will not be necessary

naj

65 230SL
68 280SL

[andre]

Thanks Naj, this is what I was looking for (read this a couple of times)   I guess I spend more time looking at the pics looking for the hole.

"Right where the return line ends there's a small hole right at the bottom where fuel enters the flower pot when the tank gets low"

I cleaned the tank again a couple of time and get almost nothing in the screen and much better flow now (good sign).  Next is getting the filter out of the fuel pump as the hose flange is stuck. I suspect, I could just reverse the polarity on the pump and "blow the stuff out. I'm going to stick a prefilter in line anyway.

[Naj ✝︎]

Hi, Andre,

 

quote:I'm going to stick a prefilter in line anyway

What prefilter are you going to use. In my view, the small plastic ones used in carburettor engines may not allow enough flow rate.
Besides, you need one with a 12mm fitting.

Since you have a spare pump now - I thought I would mention this. You can use it to pump fuel into the tank thru the return line into the flower pot. Just 2 or 3 litres will be enough to get the car started.

naj

65 230SL
68 280SL

[graphic66]

You can get real high flow filters at a marina. They make ones for boats that have spin on filters as big as an oil filter with water separator capabilities. These are about $30.00 and are overkill for the situation but it may help until you pass the contaminants.

[knirk]

Andre,
I tried to reverse the polarity on the fuel pump to blow out dirt. I let it run for about 30 seconds. Afterwards – just to be sure – I removed the filter and it still had a lot of dirt in it.
http://www.sl113.org/forums/uploaded/knirk/2005617173851_fuel%20filter.jpg

Hard to say how much more dirt present without the blow-out procedure.


Per G. Birkeland
69 280 sl aut 834
Norway

[glennard]

quote:Originally posted by naj

Andre,

This may answer your 'flower pot' question:
http://www.sl113.org/forums/uploaded/ja17/20047104938_illate%20tank,%20flower%20pot%20illus..JPG

Also, have a look at the tank tour:
http://index.php?topic=1712&whichpage=1
 

quote:I think I drained the tank, turned the car upside down, and flushed and vacuumed it.

I trust this will not be necessary

naj

65 230SL
68 280SL

'upside down'-  just to see if you're paying attention!

[andre]

I was thinking something like one of the filters with the trap.  I saw one locally once now I just have to remember where.

http://topyauld.en.alibaba.com/product/50005961/50039182/Auto_Parts/Plastic_Fuel_Filter/showimg.html

[mdsalemi]

Andre,

You can see my similar posts in the past month or two on this issue.  After all kinds of discussions of blowing out lines, cleaning screens, filter, etc. it turned out to be the fuel tank itself, slowly self destructing after 30+ years of service.  Fine rust would form on the inside, would work its way to the fuel filter then the larger particles eventually clogging the screen.  I lived with the problem for 2 years, working every angle to avoid the inevitable...

If your car ever sat unused for any serious length of time don't rule out this possibility. It's an easy fix albeit quite expensive as a new fuel tank is about $950...


Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[knirk]

SLS in Germany lists a new fuel tank for (250-280sl) 435 Euros. The 230sl tank is almost double price at 801 Euros.
http://213.239.220.84/bin/dbframes.phtml?mid=IN02

Per G. Birkeland
69 280 sl aut 834
Norway

[mdsalemi]

quote:Originally posted by knirk

SLS in Germany lists a new fuel tank for (250-280sl) 435 Euros. The 230sl tank is almost double price at 801 Euros.
http://213.239.220.84/bin/dbframes.phtml?mid=IN02

Per G. Birkeland
69 280 sl aut 834
Norway

Be aware of what you are looking at...I think at least one of the tanks that they list is a repro.  K&K here in Michigan had reproduction 280SL fuel tanks made at half the price of a factory tank, but they had two little problems--first, they didn't fit properly which made installation for those who bought them a real "bear" as we say, and second, they leaked.  I don't know about you but this would have me kicking and screaming.  If a part doesn't fit, and doesn't work, what the heck good is it, and how are you saving any money?

Do your homework before you invest in a part of this magnitude; I did, heard of these problems and went with a factory original.

Also, shipping a single bulky part like this by your self overseas would cost quite a bit of money, so factor that into your decision.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[knirk]

Good point Michael,
I may need a fuel tank in the near future so I will e-mail SLS and ask for some more information.

Per G. Birkeland
69 280 sl aut 834
Norway

[knirk]

I asked SLS to comment on our discussion about aftermarked fuel tanks, and here is the answer:

you can also post my opinion in your web-discussion:
Our fuel tanks are reproductions but almost a later and more developed version than other companies are selling. Our fuel tanks fits and if one rubber has to be turned a little bit, you have got to decide yourself if you want to pay doubleprice for not turning a bit...
But it fits without any problems. None of our tanks are leaking! If so (never happened yet), it's a complaint and you are getting a new one. Just good responses yet from our customers, so we will further sell them.

Best regards

Bastian Petersen
SLS GmbH


Per G. Birkeland
69 280 sl aut 834
Norway