reserve fuel light

[mcnevermind]

When the reserve fuel light comes on in a 1.8 190e how longs left in the tank? a few miles or plenty

 

[EuroCLK320]

When the reserve fuel light comes on in a 1.8 190e how longs left in the tank? a few miles or plenty

It depends how fast you drive.. :smile: I prefer not to risk dragging the dregs out of my tank though.. god only knows what might be lurking in there.

 

[stwat]

Just had a quick look through my manual for you. The reserve part of the tank holds 7L.

Stu

 

[sunking101]

I've heard that a lot, about not running the tank right down due to dregs in the bottom but isn't the fuel pump at the bottom anyway? Won't it suck whatever is at the bottom regardless of how full the tank is? :?

 

[tom7035]

Dragging 'dregs and dirt' from the bottom of the fuel tank is a fallacy. Lord knows I've dregged a few score fuel tanks dry in my day and never posed the slightest problem.
Just the same I wouldn't recommend it because of the sheer inconvenience!

 

[philharve]

Hi All

I usually fill up when the fuel gauge needle is approximately midway through the yellow LED region. The fuel tank holds 69L, including reserve, and I usually end up putting in 58/59L. By my reckoning that means there is about 2 gallons remaining in the tank when I visit the filling station. Two gallons translates to about another 60+ miles before we hit the dregs.

What happens if the needle falls below the yellow LED region? Do you get a second 'urgent - fill me up' warning?

Can someone please confirm whether the connection between the fuel tank and the fuel gauge is a simple 1 or 2 wirelink and there isn't a processor intercepting the fuel level signal and outputting a signal to drive the fuel gauge needle, the yellow LED and any other associated instrumentation?

The reason for my inquiry is that I've noticed that once the fuel warning LED comes on, it doesn't flash as the fuel sloshes around in the tank. Onc on, it stays on. However, if the car is switched off and then on again, the needle can appear higher up the gauge and the yellow LED may be off. I wouldn't expect this behaviour if a simple 1 or 2 wire connection was involved. The readings would be consistent.

REGARDS Phil

 

[EuroCLK320]

On the same vein... if you do run out of petrol completely with a modern fuel injected engine is it going to pose any problems trying to start it again?

 

[SLinKyjoe]

2 things.
1. It does say in the handbook, that MB advise against running out of fuel.
2. In my book it says the fuel lamp will light up at around 7-9litres and the dash display warns of reserve fuel, however the yellow led doesnt go off until you have tanken the tank contents beyond 15litres.

Dunno how it works but there is no red section on my fuel gauge and it is pretty accurate.

 

[Mr Chippy]

Can someone please confirm whether the connection between the fuel tank and the fuel gauge is a simple 1 or 2 wirelink and there isn't a processor intercepting the fuel level signal and outputting a signal to drive the fuel gauge needle, the yellow LED and any other associated instrumentation?

The reason for my inquiry is that I've noticed that once the fuel warning LED comes on, it doesn't flash as the fuel sloshes around in the tank. Once on, it stays on. However, if the car is switched off and then on again, the needle can appear higher up the gauge and the yellow LED may be off. I wouldn't expect this behaviour if a simple 1 or 2 wire connection was involved. The readings would be consistent.

REGARDS Phil

The usual setup is two independent systems.

The gauge works off a float system, and the light works off a Thermistor mounted near the bottom of the fuel tank. The thermistor is always trying to warm up but the fuel keeps it cool, which in turn keeps the light off. Then when the fuel level drops lower than the thermistor, it warms up and the light comes on. Usually there is some flickering because, as you rightly say, the fuel slops around. It may be that in some cases the thermistor will operate a latching relay that will only reset once the ignition is turned off, so that the light will be either on or off, no flickering.

 

[philharve]

OK, I will buy this explanation.

I've never heard of a thermistor being used in this kind of application before but I am familiar with the temperature-dependent characteristics of this type of resistor. This may well explain the slightly different fuel level readings I get taking one day with another. Overnight the thermistor cools and may produce a different reading when the car is next started. I instinctively knew that there was more to fuel level monitoring than a simple float system.

Thanks Mr Chippy.

REGARDS Phil

 

[pascal]

Well on 124s there is a seperate wire coming direct from the sender for the reserve light, suggesting there may be another sensor besides the float on the sensor.

PS: mine has a 10L reserve of a total 80L (by the book). If you filled it up completely, immediately after light comes on, and subtract that from total, you'd get the answer, assuming the total MB give is total usable, which I doubt.

Ran out in a 3L 124. The only way it would start was using plenty of throttle.

PS: I stick to a rule of about 30 miles max after the light comes on, and have never ran out since.

 

[philharve]

I covered 40 miles today and the needle on the fuel gauge was between the yellow indicator and the '0' mark. The indicator had been lite for quite some time.

I filled up at the filling station when the needle was resting on '0'. I put 61 litres into my 69 litre tank which, by my reckoning, gives me something like another 50+ miles before the tank runs dry. I wonder if the needle can fall BELOW the '0' mark?

It sounds as though that when the yellow 'low fuel' indicator lites there is somewhere between 10 - 15 litres remaining in the tank. That's quite generous, maybe giving another 100 miles range. Can't complain about that. Better plenty of warning than none at all.

REGARDS Phil

 

[230K]

Hi

When i had the C230K and run out of fuel it was very easy started again.

Different story with current E300TD, book says it holds 70L, after running out i could only get 73 litres in. Reserve is 9L and at best she does 70 miles on the light before running out, 2gal @35mpg seems to be about right.
When restarted car always shows slightly less fuel than before it was stopped, this will rise again after about 5 mins.

My observations, anyone similar??

230K

 

[steve kane]

I would only add that our C250D has what seems to be a really accurate fuel gauge, in that when it reads Half Full it really does seem to be the case, the problem of the fuel gauge falling faster as the tank empties does not seem to apply to the Marc, if it says half full then we know we have got approx 300miles of driveing still to go,
Steve.

 

[philharve]

Hi Steve

I infer from your comments that your C250D's theoretical range is somewhere in the region of 600 miles on a full tank? Do the deisels have an extra large tank, say 80 litres?

REGARDS Phil