Low fuel light (revisited)

[lloyd]

I asked about the existence of this light some time ago*. While this warning light has never been a priority, I took a closer examination without success. Before throwing in the towel, perhaps you folks have some "bright" ideas.

They are perhaps not the most accurate of measuring devices, but my gauges are fairly steady. The fuel gauge typically reads full, half or empty. When the fuel tank is low - but not empty, the gauge reads empty. It has been that way as long as I can remember. On that note, the only evidence I have a low-fuel warning light may have been some passing flickering. Maybe it was only "wishful flickering."

I recently pulled the sender/float assembly in the tank to check for binding. With the ignition on, I could get the gauge to register evenly as I fiddled with the float, but I could not get any low fuel light illumination. The float did not appear to bind at all. I previously removed the bulb and checked it both for corrosion and continuity. It seemed fine. I suppose the plug socket or the circuit board could be buggered up, but I hope that is not the case.

If someone knows, is the low fuel warning light triggered by the fuel level sending unit or is there something else one might consider. One would think that if the gauge reads empty so might the warning glow, but such is not the case. Any constructive thoughts would be appreciated.

Thanks in advance.


*http://e9coupe.com/forum/viewtopic.php?t=190&highlight=low+fuel&sid=1d7a5e8884cb9ab5b02cbbc50f0a7f30

 

[Malc]

lloyd,
The warning light is "triggered" by contacts on the float mechanism. I would consider the following points and steps:
1.. Remove float sender assembly, using a multimeter test for smooth varing resistance (guage input) and an "on/off" contact for the low fuel.
2.. Check that the earth(ground) to the tank / Sender etc is good.
3.. With the sender removed, but reconnected, ignition on, move float to see if guage responds and bulb illuminates
4.. If the guage works but the bulb does not then I would suspect the bulb / bulb holder etc.
5.. If sender and "switch" ok, and bulb and bulb holder ok then I would suspect the wiring, instrument PCB

Sometimes the tank may not appear to be "empty" enough for the warning light to illuminate. THis can be due to various reasons such as
1.. Sticky float
2.. Damaged / dented tank
3.. Dirt and rust in tank
4.. Wrong sender unit
5.. Float hitting the bottom of the tank before the low fuel contact is made
6.. Bent, wrongly adjusted float arm (if that type of sender unit).
7.. Float stuck before contact made, "tube" type sender
8.. Often a "low" reading gauge is due to a bad earth. Ie reads "empty" with plenty of fuel in the tank.


HTH
Malc

 

[Malc]

I forgot to add....
A gauge reading empty but no fuel warning light is a common "problem" on the Saab 900, the "classic" type (1979 - 1993).
This is most commonly due to bad earthing/wiring connections/instrument connections

The gauge on my daily hack will be below the reserve mark and reading less than empty before the fuel light will come on.
It has a 70 litre tank and "appears" empty when there is over 30 in it. One day I got brave.....
The fuel light came on permanently when there was 10 litres left in the tank.
If you feel brave too then put a full Jerry can (20 Litres) in the back of your car and just keep driving till the fuel light either comes on or you run out of petrol!
Then you will finally know......
Malc

 

[lloyd]

Thanks for your replies.

As noted above, I had the sending gauge/float assembly out of the tank and the fuel gauge moves smoothly in concert with float movement. The light never glows even with the float at its lowest level. Appreciate your mentioning of the Saab grounding issues. Having, for the most part, eliminated the sending unit as the source of the problem, I think I have a ground problem elsewhere.

Naturally, no sooner than you posted your reply, I was unable to start the vehicle. In a fit of frustration, I tugged on the pristine cable attached to the pristine starter, and the car started. What this portends, I know not. Can't wait for the brittle original fuel injection wiring to start talking to me at the wrong time.

I doubt I can attend to this benign warning light issue until science determines what is lurking in the tank. Pulled the sender/float while in a poorly lit garage. Wished I had not looked in the tank. Don't think this coupe has been to Scotland, but I think I saw some mutant haggis with flippers in there. Wont sleep well till this bilge is gone.


Thanks again

 

[Arde]

You found biological diversity inside the tank? Neat. Forget the light, you may train these crits to tell you when the tank is almost empty. The first E9 with molecular biology instruments. Send pictures!

 

[lloyd]

Loch Ness Amoeba??

Arde, because of your special interest in things terrestrial and otherwise, I felt compelled to provide an update on the what's in the tank adventure. (It turned out to be trash and you might want to stop reading now!)

Not sure what Lord Carnarvon or Dr. Who might say, but this examination is a lot less daunting in broad daylight. (Considered using a remote submersible camera, until I realized it was probably being used somewhere in the North Atlantic.) Preliminary findings indicate broken fuel sender gasket remnants - of unknown origin and possible painting remnants including a torn plastic sheet or a possible sandwich wrapper. I expected to find an old rubber boot and an anchor, signed by Captain Kidd, but I am glad I did not- because some foreign government might seek to lay claim. I am on a budget and thus decided not to forward these specimens to the laboratory for further analysis. I suppose the conspiracy theories will never be put to rest now.

Never personally recall needing to replace gaskets and certainly would not have left anything in the tank, had it been permitted to fall in.

Much of this is guess work and "the Yard" is to busy to take my calls anyway. Admittedly, from time to time, das auto has not always been in my exclusive control nor did the tank always have a locking gas cap. I would like to think otherwise, but it is possible some inconsiderate bloke, or the female equivalent, confused the fill-up tube with a garbage disposal. Tank was removed many years ago, but perhaps the floatsam went unnoticed because we were too focused on other areas of the car being painted or rebuilt. Because of time constraints and environmental concerns, use of the fish strainer, the three prong pickup tool and replacement of the filter will have to do for now.

The low fuel light continues not to work, and I expect it will remain that way for quite some time.

On an unrelated note, Malc used the term “jerrycan.” I have always assumed the label is one given by the Brits for German fuel containers. But what do the Germans call it?

 

[Malc]

Jerry Cans

The term Jerry can is "Brit" Speak for a metal petrol can.
Asked my Dad (91 years old and still a hoolgan behind the wheel) to confirm where the term comes from in the UK.....

During the 2nd World War the Brits were putting petrol in tin cans, basically big baked bean cans. THese had to be opened and could not be resealed....Not the brightest idea

Meanwhile The german army where having a drive around the Western Desert and fancied a trip to see the pyramids just down the road near Cairo. The lack of handy petrol stations on the way meant they had to carry extra fuel in handy 30 litre reusable cans.....
One thing lead to another and both army's bad habit of leaving litter everywhere. meant that some Brit soldier found one of these handy cans and thought "I can make money out of this"
Sadly he didn't as the army (met with some resistance in the upper ranks) realised that this was a spiffing idea and copied it. I think they flogged it to the RAF, but the Navy didn't think they were big enough :wink:
I think they even flogged it to the US Army

So the term "Jerry Can" originated from the UK army in the Western Desert and is still in use today

Sorry for being a bit of an Anorak :roll:
Malc