gas gage - sending unit confusion

[A Dalton]

As Lewis points out..With these cars being as old as they are, if you are not the original owner or know the history well, it is difficult to tell what parts have been changed, re: tank/sender/gauge.
 As I posted earlier  ,if a 100 ohm  test resistor in place of the sender registers 1/2 tank on the gauge, your fuel level indicator system should be coupled with the earlier external float sender unit.

 Resitance specs are from  '59 BBB

[Mike Webster]

A Dalton

Yoe hit the nail on the head. I am the second owner of this "restored" car. God only knows what parts are in it.

Mike in Detroit

[Mike Webster]

Scholars,

I finally received my new float-lever style sending unit from SLS and installed it Saturday. When I turned the ignition on the gage read empty on a 3/4 full tank. So I took the unit out and manually moved the float while a friend observed the fuel gage and found the gage reads full when the float is in the empty/down position, and empty when the float is in the full/up position. I am now the proud owner of two new VDO sending units, neither one getting the job done. Any ideas?

Mike in Detriot
1966 230sl silver/red

[A Dalton]

Do you have any in between readings when you go through the range??
..if not [ reads full or empty only] , then I think you may have the wires crossed at the sender for the gage feed and the reserve lamp feed .. that would explain the full/empty only readings when operating the float by hand.
 So, check my first queestion and post finding...

[Mike Webster]

A Dalton,

Yes, the indicator moves up and down the range of the gage with corresponding movement of the float, only in the opposite direction. However,I cannot recall the low fuel light comming on (I know that the light does work). Anyway, if the wires are crossed, why does the cylindrical style work?

Mike

[A Dalton]

<<why does the cylindrical style work?

>>

 If the cyl works , why are you using another style???

 Do you have an ohm meter???

[Mike Webster]

A Dalton,

This is what happens with the cylindrical style unit. With the tank full, the gage reads full. After running about 100 miles, the gage shows half full. At 200 miles, the gage shows empty, with the low fuel light on. At the pump I check my fuel usage aginst the odometer and the car runs about 18-20 mpg. Assuming the tank is 17 gallons, the tank should rum empty around 300-340 miles.

Mike

[A Dalton]

I see .. that seems a little different than your other post, but I do believe I have some info for your problem..
 First of all , all 65/l tanks take the float/rod sender unit. All 82/l tanks take the cyl unit.
 Second , you can not use a cyl sender with an early gage and vics/versa..
 So, you have a 65/l tank with the newer sender and gage , which will work, but will not be accurate/calibrated to a 65/l tank, as they belong in an 82 l tank..
 .. That is why I mentioned using a 100 ohm test resistor back in place of the sender unit in an earlier posting.. if that resistor test results made the gage register 1/2 tank, you then would know  you have the earlier float system and that you also have verified the earlier gage calibration...

[Ben]

But 17 gallons is 65 litres !

 

quote:This is what happens with the cylindrical style unit. With the tank full, the gage reads full. After running about 100 miles, the gage shows half full. At 200 miles, the gage shows empty, with the low fuel light on. At the pump I check my fuel usage aginst the odometer and the car runs about 18-20 mpg

........my own 230SL behaves pretty much in the same manner, though I normally get the fuel light "on" at about 215 miles and can stretch maybe 240 from a tank !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[hands_aus]

one gallon = 4.5456 liters
65 liters = 14.3 gallons (imperial)

I think the floater sender unit is from a sedan of the same period.
I vaguely remember this info from a previous discussion either on here or the old Yahoo site.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Ben]

quote:one gallon = 4.5456 liters
65 liters = 14.3 gallons (imperial)

......Bob my 230SL owners manual states 14.2. Imp. Gallons/17.2 US gallons/65 litres !

If you made a mistake whilst calculating mpg figures you could end up with quite a difference in range in you Pagoda !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[hands_aus]

True Ben,

Your original post mentioned 17 gallons = 65 liters and I assumed you would be thinking imperial gallons not US gallons, because the discussions on here always refer to the tank as being 18 gallons (obviously they mean Imperial gallons)

I made a spread sheet in which I enter 'liters used' and 'distance travelled in miles' and it converts to liters/100km, km/liters, MPG Imperial, MPG US, miles to KM, US gallons, IMP gallons.

It is very informative.

I always think in Imperial MPG for my 250SL and Km/liter for my Toyota Corolla.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto