Tank low light

[Bwana]

I was reading the owners manual last night (what a concept! reading the instructions!) and noticed it mentions the charge and oil pressure light come on when the key is turned to the "on" position but there's no mention of the "low fuel" light. Mine doesn't come on when I first cycle the key and I'm too chicken to run the tank down that low.

Is the low fuel light supposed to illuminate when the key is first cycled? If not, I'll probably put a gas can in the trunk and see just exactly far I can go (on a quiet road of course)

 

[Stevehose]

It doesn't come on unless you're running low on gas - it will flicker at first then go completely lit. You could pull the sender unit and test it as an option to running the car out of gas.

 

[30csl]

Yeah - same as on mine.

Its funny those little warning lights are one of the collest things on the cs for me - the colours are brilliant. I remember being a kid and getting in the car and turning the key - battery and car were pretty dead but the dash lights would still illuminate

 

[m5bb]

It doesn't come on unless you're running low on gas - it will flicker at first then go completely lit. You could pull the sender unit and test it as an option to running the car out of gas.

Thanks I'm going to test mine. I too wondered when it would come on if at all?

 

[jmackro]

...the charge and oil pressure light come on when the key is turned to the "on" position but there's no mention of the "low fuel" light. Mine doesn't come on when I first cycle the key and I'm too chicken to run the tank down that low.

The charge and oil pressure lights come on when you first turn the key because the alternator isn't charging and the engine isn't developing oil pressure. The low fuel light doesn't come on with the key because the tank level isn't low (of course, it will come on if it is low). In other words, these are "dumb" indicators that simply display what is actually happening. It would take some electronic "smarts" to trigger the lights for a couple of seconds after the key is turned - something that was not installed on cars in the early 1970's. That lack of electronics is part of what makes these cars so charming.

It doesn't come on unless you're running low on gas - it will flicker at first then go completely lit.

Yes, a nice feature - the flashing gets your attention. Nothing fancy is needed to produce the flashing - it's just the fuel sloshing in the tank, causing the float to move up & down, and in turn switching the light off & on. Once the fuel level gets low enough, the light stays on continuously. By the 1980's the engineers at BMW had no doubt developed a $500 computer that reproduces this effect and generates revenue for the dealers.

 

[Bwana]

Excellent explanation! Thanks!

I'm so used to the $500 computer (or more) that's in all my vehicles (including a couple of my bikes) that turn the idiot lights on that it never occured to me that these might simply be "dumb" instruments.

 

[DaveG]

May not be relevent....I have the E24 Fuel pump and sender in My E9 (MS3 EFI)....The level sensor is not quite right for the E9 gauge.
With this set up my low level light comes on with ~2 gallons left....and the gauge is well below the red mark.....I tested it while I was prepping the car for paint...
DaveG

 

[Honolulu]

Anyone planning to remove the fuel gage sender should consider having a spare, new o-ring ready for the reinstallation. It's my understanding that they swell when exposed to gas (installed) and not sure if they can be relied on to shrink later. The o-ring (whose size I don't have right here) is not difficult to find at your FLAP or an industrial bearing supply house.

Bad or old sender o-ring = fuel smell in car, possibly a splash in the trunk. Not generally regarded as a good thing except to drivers of the BMW 3.0CS where it is a feature, not a defect!

 

[m5bb]

Anyone planning to remove the fuel gage sender should consider having a spare, new o-ring ready for the reinstallation. It's my understanding that they swell when exposed to gas (installed) and not sure if they can be relied on to shrink later. The o-ring (whose size I don't have right here) is not difficult to find at your FLAP or an industrial bearing supply house.

Bad or old sender o-ring = fuel smell in car, possibly a splash in the trunk. Not generally regarded as a good thing except to drivers of the BMW 3.0CS where it is a feature, not a defect!

Took my sender out tonight to test the low level light. Just rested sender at top of tank, turned on key and bingo a white light showed up in the dash.
Yes, my CS smells like gas frequently. The area around the sender was dry but will check again after driving.
I bought a small fire extinguisher to keep in the trunk.
We were coming home from the beach a couple weeks ago (not in the coupe)and there was a car on a exit ramp about 3/4 the way up. The hood area was in flames.
What a helpless feeling.
So Gary says get a fire extinguisher.

 

[Stevehose]

Search the forum for trunk smell, if your o-ring isn't leaking and you have gas smell it's probably the vapor cannister. I vent mine out the bottom of the trunk, not through the old, cracked blue plastic tube to the crusty charcoal filter. No smell. PM me if need help.

Took my sender out tonight to test the low level light. Just rested sender at top of tank, turned on key and bingo a white light showed up in the dash.
Yes, my CS smells like gas frequently. The area around the sender was dry but will check again after driving.
I bought a small fire extinguisher to keep in the trunk.
We were coming home from the beach a couple weeks ago (not in the coupe)and there was a car on a exit ramp about 3/4 the way up. The hood area was in flames.
What a helpless feeling.
So Gary says get a fire extinguisher.

 

[m5bb]

Search the forum for trunk smell, if your o-ring isn't leaking and you have gas smell it's probably the vapor cannister. I vent mine out the bottom of the trunk, not through the old, cracked blue plastic tube to the crusty charcoal filter. No smell. PM me if need help.

Thanks Steve, good tip.

I know the canister is gone so probably venting in the trunk or ??
I will perform this fix soon.

Gary

 

[deQuincey]

Anyone planning to remove the fuel gage sender should consider having a spare, new o-ring ready for the reinstallation. It's my understanding that they swell when exposed to gas (installed) and not sure if they can be relied on to shrink later. The o-ring (whose size I don't have right here) is not difficult to find at your FLAP or an industrial bearing supply house.

Bad or old sender o-ring = fuel smell in car, possibly a splash in the trunk. Not generally regarded as a good thing except to drivers of the BMW 3.0CS where it is a feature, not a defect!

as to the o-ring, consider it always to be nbr, nitrilic rubber, other material different than nitrilic will deteriorate quickly and wont do its function

 

[deQuincey]

Took my sender out tonight to test the low level light. Just rested sender at top of tank, turned on key and bingo a white light showed up in the dash.
Yes, my CS smells like gas frequently. The area around the sender was dry but will check again after driving.
I bought a small fire extinguisher to keep in the trunk.
We were coming home from the beach a couple weeks ago (not in the coupe)and there was a car on a exit ramp about 3/4 the way up. The hood area was in flames.
What a helpless feeling.
So Gary says get a fire extinguisher.

a tip from a former fire safety engineer, (including computer aided symulations and correlation real tests)

do not place the fire extinguisher in the trunk, find a place next to you, maintain it at hand, mine is secured front - below the passenger's seat, so i will only have to describe a small circle with my right arm to get it

a reasonably sized fire ext. (less than one kilo) will be able to fight very small fires, seconds count, so if you have to stop the car, get out, go to the trunk, open it (eventually go back for the keys to open), find it, enable it, and operate,...done, the whole car is in flames...:roll:

if possible bring two and not one, (the failure ratio in fire extinguishers is very high, ...even in regularly checked ones)

a blanket, or thick towel can be useful in some cases to withdraw the oxigen from the fire spot

 

[Stevehose]

I took the tube leading into the plastic tank and routed it out through a hole in the trunk floor just aft of the gas tank. Then I capped off both nipples on the expansion tank and the other tube that goes from there to the engine compartment with vacuum caps from the parts store. I can post a pic later if you need. Also check that your gas cap and the small rubber connection hose form the filler tube to the tank are sealing properly.

Thanks Steve, good tip.

I know the canister is gone so probably venting in the trunk or ??
I will perform this fix soon.

Gary

 

[blumax]

White low fuel indicator--

will start to flicker with about 2 1/2 gallons in reserve and become a solid glow when you have around 2 gallons left. This is based on field testing--unplanned--with the BLUMAX. Tanks on early e-9's hold 18.5 gallons--in later models--believe them to be the same capacity.