Fuel filling, fuel tank capacity & fuel gauge

[babarsheikh]

When I fill up my 280SL with gas, it seems to get full really quickly,seemingly after about 12 gallons.  According to my manual, the capacity is 18 Imperial gallons which is about 21.7 US gallons?  I know reading some threads that the filling causes some issues and it requires that you just fill really slowly but seemingly after about 12 gallons  my fuel gauge needle shows that tank as pretty full and I feel that gas is getting near the top.  Next time I fill up I will make sure I fill to the brim and make sure that the tank is really full but in the meantime...

I am thinking it might just be a very basic issue based on ignorance on my part: maybe I am just filling my tank too early i.e. when there is alot of fuel left in my tank.  I don't wait until any light goes on, just when it is just above the "R", so maybe thats the issue?  I dont have a gas can backup and am just parranoid about the car dying with no fuel.  

At what point do others fill up their tanks?  Also wondering when others fill up, at what point does the automatic pump nozzle shut off kick in,  after which "slow filling" is required.

Thanks,

Bobby
1970 280SL

[J. Huber]

Hey Babar.

I tend to fill mine up when I get down to about a 1/4. I always hold the nozzle when filling because the kickback of the pump shut-off can easily knock the nozzle out (hitting the bumper on the way to the ground and making a big mess!). I continue to fill it after I feel the shut-off. Slowly working it until I actually hear the gas coming up the tube. I bet a couple more gallons go in this way. This way I am sure its full and if checking mileage, this is important.

I have let the tank go low enough to see the red light -- mainly to find out if it worked. I believe there are still a couple gallons at this point -- but like you, I'd hate to "push it!" (literally)...

James
63 230SL

[babarsheikh]

Thanks James.

Couple of questions for you:

1) Where is the needle on the gauge when the light goes on?
2) When you fill up when there is about 1/4 tank left,how many gallons can you fit in?
3)As I said, I fill up when the needle is above the 'R' but the needle goes alot lower (e.g. when the ignition is off") so does it seem strange to you that I only get about 12 US gallons when the needle is at that stage? I guess I am wondering what the high and low points of the gauge are...

Thanks again..

quote:Originally posted by J. Huber

Hey Babar.

I tend to fill mine up when I get down to about a 1/4. I always hold the nozzle when filling because the kickback of the pump shut-off can easily knock the nozzle out (hitting the bumper on the way to the ground and making a big mess!). I continue to fill it after I feel the shut-off. Slowly working it until I actually hear the gas coming up the tube. I bet a couple more gallons go in this way. This way I am sure its full and if checking mileage, this is important.

I have let the tank go low enough to see the red light -- mainly to find out if it worked. I believe there are still a couple gallons at this point -- but like you, I'd hate to "push it!" (literally)...

James
63 230SL

[enochbell]

I was going to correct you concerning the 21.7 gallon tank (my 230sl is 17.2) until I looked it up.  Holy tank capacity, gas man, that's a lot of petrol!  Was there any good reason to install that huge "ballast" in these semi-light cars?  Range?  Sign of the times?  

As far as the problem itself, I think it is more likely the guage or sending unit.  The acute bend in the filler neck makes it hard to fill on "automatic shutoff" mode, I always have to fill slowly and hand-modulate the pump.  As long as you are doing that you should be able to fill the tank.  Now, assume 18 mpg and drive it for about 350 miles, ignore the guage.  Did I mention that it would be a good idea to bring a spare gas can (full) with you on this test?

Best,

g

'64 230sl, fully sorted out...ooops, spoke too soon

[Naj ✝︎]

Bobby,
The 230s have a 65 litre tank while the 280s have an 80 litre tank.
I filled 280 up yesterday from 1/4 tank. The gage is quite accurate at the lower end. It took about 60 litres. Nozzle popped at 50 litres and then further 10 liters by holding the nozzle just a couple of inches into the tank filler. I can fill it to the brim without spilling if I do it with patience.
Gage would have still shown full if I stopped at 50 litres but would start going down after 20-25 miles. If filled to the brim, it starts going down after 80 or so miles. Gage is less accurate at the top end.
Light goes on at 10 to 12 litres remaining in the tank

naj

68 280SL

[J. Huber]

Hey Bobby, I think the others have summed it up pretty well. Here would be my responses to your questions:

Originally posted by babarsheikh

Thanks James.

Couple of questions for you:

1) Where is the needle on the gauge when the light goes on? Not sure exactly but pretty far down there: I was nervous checking the light and was surprised that when I filled up, it wasn't that close to empty.
2) When you fill up when there is about 1/4 tank left,how many gallons can you fit in? I have the smaller tank -- I'd have to say around 12.
3)As I said, I fill up when the needle is above the 'R' but the needle goes alot lower (e.g. when the ignition is off") so does it seem strange to you that I only get about 12 US gallons when the needle is at that stage? I guess I am wondering what the high and low points of the gauge are... I agree with Naj that the needle is most accurate as it gets lower. Except for when its full to the brim, mine tends to jump around a bit until it gets low.



James
63 230SL

[Benz Dr.]

Only fill the tank full to the top if you plan on driving for a while to lower the fuel level in the tank. If you fill your car at night then take it home close by gas can come out the vent line when it gets hot out through the day.
 I '' learned '' this the hard way filling diesel tanks on farm equipment at night before I left for the day. Usually a big mess by noon the next day.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[n/a]

Bobby

J. Huber mentioned this but maybe we should emphasize that there are two size tanks in the 113 cars.  The cars with the vertical spare have a much smaller tank than the ones with the spare that lay flat.  As in most things it is a trade off.  With the flat spare you have a longer range with a full tank, but very little space for luggage for the longer trip.  With the vertical spare,  you have room for more luggage, but a markedly decreased driving range, and an ugly spare tire well hanging down under the car.  I am not sure which cars had what spare tire configuration.  I do know I have a US 230 SL with the vertical spare and a euro 250 SL with the horizontal spare configjration.  Maybe someone else can shed some light on the differences.  

Good Luck

Iverson

Good luck

Iverson

[graphic66]

The fuel level sending unit has a small labrynth at the bottom to let the fuel slowly find the level in the tank and not have the needle bouncing all over the gauge as fuel sloshes around. I kept trying to get the reserve light to work and it would only come on after it was parked for a while. It turns out that the small plastic labrinth at the bottom of the sending unit in the tank was partialy blocked with rust particles and wouldn't let the fuel pass through quickly enough to register on the gauge unless it sat long enough. I pulled the sending unit from the tank via the trunck and found the obstruction and the reserve light started working as normal. My tank was replaced and I'm sure the sending unit was not cleaned at the time. The reserve light doesn't come on until the gauge is dead on E, and it has enough fuel to get to a gas station. I love to see that litlle orange light working but hate the consequences, another 50 bucks guzzled and worth way more than that in the delight of driving the finest car ever made.

[DavidAPease]

To clarify Iverson's observations a bit: According to at least one source, the vertical spare mounting of the 230SL was abandonded in November of 1964, in favor of the horizontal mounting.  (I believe that this was due to ground clearance problems/complaints.)  However, the smaller tank continued throughout the 230SL series.  The larger tank was introduced in January of 1967, with the start of 250SL production.  

When I asked whether I could fit a larger tank in my 1966 230SL, I was told that the fuel pump on my car would be in the way, and I'd have to switch to the later, smaller pump as well.

-David Pease
'66 French 230SL

[Naj ✝︎]

David
 

quote:When I asked whether I could fit a larger tank in my 1966 230SL, I was told that the fuel pump on my car would be in the way, and I'd have to switch to the later, smaller pump as well.

I was told by SLS that the bigger tank would fit the 230SL as long as you have the horizontal spare wheel.

My 280SL had the old large fuel pump and the pump mounting is exactly the same as the 230. I think the larger tank would fit the 230

naj

68 280SL

[DavidAPease]

Naj,

Thanks for the info.  I'll love to try it, when the budget allows.

-David Pease
'66 French 230SL

[Naj ✝︎]

David

 

quote:Naj,

Thanks for the info. I'll love to try it, when the budget allows.

At least at SLS, the bigger tank is a lot cheaper [:p]
The extra bit goes in the space created by the missing early spare wheel well.

naj

68 280SL

[Benz Dr.]

The tank is larger on the left side of the car. I think the large tank will it any car.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[babarsheikh]

I have been working on my trunk.  I was sanding off the surface rust in preparation for thh primer and decided to take a couple of pictures of my fuel tank just to see what others thought and that it was all looking OK.  Here are the pictures.  I have the Haynes book and there is a black and white picture but have not seen another's trunk in much detial.  Just wondering if there is anything weird looking about it? Thanks...


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[dldubois]

Bobby:

Looks good.   These cars are famous for rust in the trunk.   My car's in the process of being repainted.   I went and visited my painter yesterday and he was busy sanding away on my trunk floor...



Dana DuBois

1969 280sl
Corinth, TX

[rwmastel]

quote:Originally posted by babarsheikh

.... decided to take a couple of pictures of my fuel tank just to see what others thought and that it was all looking OK.

You don't get to the good part.  What counts is what's inside.  Did you look?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[Cees Klumper]

Strangly enough, the tank in my '69 280 SL is the smaller 65 litre one. At least, I think so, because I have once ran the car to where the 'tank empty' light came on, and very soon after that the car appeared to get fuel starvation, right as I was pulling into a gas station (in other words, I think I ran it to practically empty) and still the tank would not hold more than 65 liters. I typically fill up with approx 61-62 liters when it is almost empty. So ... it seems a PO replaced the old tank with a (used) one from a 230 SL?

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[Cortez-Campos]

I have been thinking about this tank capacity for a long time, my 280 SL should have a 82 liters tank, but I have never filled more then 65 liters on it.
After my restoration last winter, I bought an used tank from another 280SL, and it also only contain 60-65 liters.

I have never seen the light come on, but I have been very close to empty, normal I only fill 30 liters on it, but it is also a ½ tank.



Christian Cortéz-Campos

280 SL 1969 anthracite 172, with red inteior.

[babarsheikh]

Rodd,

Did not look yet.  Reading all these threads on the gunk found, I think I should take a look but for now, I am focusing on rustproofing the trunk.  I spent 5 hours sanding by hand last weekend and then this weekend bought the sanding attachment for my drill to get ever last bit of rust out. Worked great.  Is is common practice to give the fuel tank a clean every so often?

Bobby

quote:Originally posted by rwmastel

quote:Originally posted by babarsheikh

.... decided to take a couple of pictures of my fuel tank just to see what others thought and that it was all looking OK.

You don't get to the good part.  What counts is what's inside.  Did you look?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[kbailey]

My 69 has a 18 gallon tank.  The fuel back washes into the fuel fill neck because the tank is so low and the neck is almost in line with the tank.  I fill my tank whenever, but certainly within 20 miles or so of the red light coming on.  My tank stops the gas pump at 11-12 gallons and I have to pull the nozzle out far enough to get the fume/splash guard out of the line of view and watch the balance of the fuel go in at about 1/4 pump speed...just barely squeeze the handle...be careful and don't splash.  This takes a bit of time too...  It helps to park on the filling station pad with the front pointed even the least bit down hill.  You can hear the change in tone of the fuel going into the tank...just like filling up a glass.

Good luck!  Another joy of the Pagoda!  I usually have the extra time taken up by other motorists coming over to chat.

KBailey
69 280SL Cream
Black Interior
Dallas

[rwmastel]

quote:Originally posted by babarsheikh

Is it common practice to give the fuel tank a clean every so often?

Yes, every 30 or 40 years.  Actually, if the car ever sat unused for a prolonged period (over 1 year w/o starting) in it's life, then the tank should be checked.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[thelews]

I let my car's fuel run down today, so I could fill with non-ethanol gas, to when the reserve light came on (first time I've seen it work).  It took 16.25 gallons.  I can't figure out what size tank I have or how many gallons were left in reserve.  Old tank style (18) 2 gal. left, New tank (21) 5 gal. left?  That seems like a lot.  I'm number 1543 in 1967, March build.  Any ideas?

Edit: Well, looking at the technical manual, it appears I have the larger tank.  Wow, 5 gallon reserve?  That's almost 100 miles.  I'm not rushing to the gas station anymore and wouldn't have stopped to put 2 gal. in to make sure I got to the non-ethanol station today.

[mdsalemi]

John, you have a WHOLE LOT more options for non-ethanol gas in Wisconsin than we do in Michigan; one of the websites that keeps track of such things does not list many Michigan stations (small airports and marinas are included!) in populated areas.

[thelews]

The station I use is about 20 miles away.  Gives the car a nice run.

I figure I'm about 3% ethanol now, having had so much in the reserve tank.  Next time I'll know better and will put a gas can in my trunk just to be safe.