fuel gauge

[rc3064]

My fuel gauge SEEMS to work. When I fill the tank the gauge goes to full and goes down all the way to R as I drive(150 mi). But I can never fit more than 11 or 12 gallons when I fill up. I've never seen a gauge that goes from full to reserve for half a tank.

[scoot]

My fuel gauge SEEMS to work. When I fill the tank the gauge goes to full and goes down all the way to R as I drive(150 mi). But I can never fit more than 11 or 12 gallons when I fill up. I've never seen a gauge that goes from full to reserve for half a tank.

Does the amber low fuel indicator come on when the gauge says you are on R?

[olazz]

Why not fill up, zero the trip and carry a spare 5l can of fuel. Drive the the car until it coughs and runs out of fuel.
Note the Odo reading refuel from can and hey presto!

You've got a much more accurate measure of Miles per tank, or indeed miles you can drive with the fuel light on.

[rc3064]

I haven't gone quite that far on reserve I guess, my light has never come on.

[scoot]

I haven't gone quite that far on reserve I guess, my light has never come on.

You can have even more fun with this if you want - you can take out the fuel sender (unplug, remove little nuts, nudge it back and forth and UP, and remove from tank), then plug sender back into socket and see if when REALLY empty the gauge reads lower than you have seen before and if the amber light comes on...   The down-side to this is that you may need a new cork gasket, which is only a couple dollars but you want to get this in advance so that you can put the sender right back in after test is complete.  It's possible that the gauge goes lower, and that the light comes on.  Or it is possible that the gauge doesn't work right.  Or that the sender doesn't work right.

Point of clarification - if you have an EARLY 230 SL ignore what I wrote above.  I think early 230 SLs have the float-type sender (looks like a conventional gas float on an arm, etc).  Those are a nightmare.  I guess I would still take it out and experiment with it, maybe moving the arm and seeing if you get a full range of motion and if you get the amber light.  I have never been able to get one of the early style to function properly.   And you can't just replace it with the later style.


Oh!  If you have an early 230 SL and someone replaced the early float sender with the late tube sender, this could explain what you are experiencing...

[hauser]

I had some similar problems, replaced the unit and it's worked fine since then.

[jacovdw]

...I think early 230 SLs have the float-type sender (looks like a conventional gas float on an arm, etc)...

That is correct.

The early style float and lever type sender was used up to chassis number 008953 for all LHD 230SL's and up to chassis number 013302 for all RHD 230SL's.
Sadly this part has been NLA from Mercedes for quite some time.

There is an upside however, the same type of sender was also used in the early fintails (220Seb, 230S and 220SE coup/conv.).

...If you have an early 230 SL and someone replaced the early float sender with the late tube sender, this could explain what you are experiencing...

Also correct as the gauge in the in the instrument cluster is different for the early and late style fuel sender units. You cannot used the later style sender with an earlier gauge as your readings will be different.

The reserve warning light has a delay built into the circuit. Once contact is made, the light would come on after a few minutes. This is to avoid the light flickering due to contact bounce whilst driving with a tank close to the reserve mark.

The lag is typically 4 to 7 minutes.

All pagodas after the above mentioned chassis numbers should have the later tubular style sender unit. If so, then you have nothing to loose by removing it from the tank and open it up for an inspection and clean.

The usual precautions apply when working with gasoline and always replace the fuel sender gasket on the tank.

[Benz Dr.]

I had this problem with a 220SE Cab that we were working on. The 128 cars have a reserve warning light but it wasn't working. I used a 190SL sender but it never really worked properly.
We figured out the problem eventually. The float was hitting the flower pot so we bent the end in the opposite direction and now it works perferctly. It won't have a low warning light but the sender with that function is very exspensive if you can even find one. I imagine the early 230SL has the same sender and similar fuel tank except for the filler neck.

[jacovdw]

The early 230SL's with the float lever type sender unit has a 65 liter fuel tank, the same as the later 230SL's that use the tubular fuel sender unit.
The pontons used a 50 liter fuel tank, thus the height of the tank is different and consequently the installation height of the sender unit is different too.

From what I can gather, the float and lever type fuel sender used in the pontons (190c and 190Dc) is different from the one used in the early 230SL's in terms of the length of the float lever.

The differences in length of the float levers (and thus the radius of the arc the lever travels as the tank empties) accommodated the difference in the height of the tanks.

The resistance values of the senders are the same when you look at the respective levels of fuel in the tank (full, half and quarter tank respectively).
This would require further research and testing to verify though.

[Benz Dr.]

Fuel tank on the 220SE is supposed to be 62 liters and is similar to the 190SLwhich is 65 liters. The 230SL is also 65 liters so a gage from a 190SL should work.

You will need to change the way the sender mounts so it facees 180 degrees opposite to the way it would normaly install. This requires moving one of the six holes ( drill or file ) that indexes the sender so you can turn it to the proper position. The float arm swings to the right on tanks with a flower pot and to the left on the 190SL so changing the direction is critical.

[hands_aus]

Would you be able to use the later fuel sender if the fuel gauge was swapped to the 280 sl model fuel gauge?

I have issues with my early 250sl fuel level. with the reserve light on I have 38L of fuel in the tank.
The sender is a later unit which connects to an early gauge.

Are gauges more readily available as compared to early fuel senders?

[jacovdw]

Bob,

Technically you should have the correct gauge in your instrument cluster.
The changeover to the later style tubular sender unit (and gauge) occurred in the 230SL's already (manual cars from chassis number 008954 and automatic cars from chassis number 013303).

Is there not perhaps an issue with your sender unit then?

 

[hands_aus]

Hey Jacovdw,

I think there must be a problem with the sender.
Myabe I need to clean the labyrinth and give the little wires a clean.
Possibly they are oxidized.
It is a tricky job.

thanks

[studioPaGoNa]

Hello All.

Please allow me that it might be different topics.
My SL suddenly stopped at the corner and it stuck there. Finally it was towed to my mechanic. The mechanic explained me that the fuel pump was broken due to no petrol in the tank. The fuel sender unit was also found to be out of order due to the debris. I just remember that the fuel level indicator never comes on warning light in the past.
The replacement cost for the new pump is very expensive here which I was very shocked.  I cannot afford to replace the fuel sender this time. So I have to fill up petrol at 1/4 remaining in the fuel gauge.
Anyway, may I confirm if no petrol results in destroying the fuel pump as mentioned by the mechanic?

Koki
`68 280sl Moss green metallic w/Cognac

[ja17]

Hello Koki,

Running out of fuel will not destroy the fuel pump in most cases.   If you have dirty fuel tank issues make sure that the mechanic cleans the intake screen in the electric fuel pump (important, it  is located in the intake fitting of the electric fuel pump) and the filter screen on the fuel tank drain plug before you start the car again. 

Check the fuel pump fuse in the fuse box. If the pump runs when you turn on the ignition, it is most likely fine. If it does not run check to see if it is getting power.

[studioPaGoNa]

Hello Joe,

Thank you for your valuable input. I was expecting your answer to some extent, because the mechanic said to me that the fule tank as well as the tank drain plug with screen as you mentioned was found to be clear but the fuse is open.  I am wondering what happened to my pump?
As the broken pump is with me, I am trying to check if it works though as I am a layman.
The pump was already replaced by the new pump in which I paid very much.
Somehow it is too late, isn't it?

Regards,Koki