Fuel gauge reading and reserve

[911ac]

Hey,

Apologize in advance for the very simple question. I am expecting to take delivery of my first 911 air cooled (1987) tomorrow.

I have a photo from the shipping company, when they loaded the car, that is showing the fuel gauge.

I am wondering if I should have enough to drive to the gas station (around 2 miles) or if I better prepare a gas can ? I am not entirely sure when it hits the reserve.




Thanks,

[Ian Comerford]

I would take a gas can, you don’t know how long it has been that low nor how accurate the gauge is. You don’t want to suck any crap in the tank up into the system and block it

[ccallana]

Is the light actually on? If no light, you have a few gallons, you'll be fine to get to a station.

If the light is on - I think you are down to less than maybe 2 gallons - could be risky....

[Bill Douglas]

Yeah, that's 30 miles or more.

So, tell us about the car?

[Schulisco]

Porsche tells in the manual of roundabout 8litres/2.1gallons in the tank remaining when the reserve warning light comes up. Either carry a gas can or top up some litres in the barn/garage before heading to the gas station as said. You cannot rely on the gauge until you tested it by yourself.

Congrats to the first aircooled Porsche 911 & welcome to the club!

Thomas

[911ac]

Thank you all for the great inputs. I will prepare a gas can to top it up before heading to the gas station, just to be on the safe side.

I will share more about the car once it gets there!

[fanaudical]

In case it's helpful - My paranoid practice on my 911 is to keep at least half a tank of gas to keep the "stuff" in the tank in suspension and out of the fuel injection system. I have an older car with the fuel pump in the rear so some extra gas keeps the pump full.

[smadsen]

Many years ago I drained the tank on my '82 to service the screen. When I filled the tank from zero, with the ignition on, it took about 2.5 gallons to make the light go out.

[nickelplated5s]

Wasn't there a Seinfeld episode when they wanted to see how far it would go? Bring a gas can.

[Quickstep192]

There was an episode of Mom where they called it “riding the zero” - trying to see how long you could go with the light on… Guess how it turned out

Bringing a can sure ain’t gonna hurt.

[spuggy]

Can full of nice fresh gas would be a no-brainer I think.

Gas gauge is basically a voltmeter, is affected by system voltage. If motor isn't running, no alternator charging the battery - so only the "at-rest" battery voltage driving the gauge.

The reserve light is a switch and isn't...

Noticed this when I swapped out my Bosch alternator for the CR 175A one - a modern alternator, which, unlike older tech ones, puts out over 14V at idle. My reserve warning light now switches on with the gauge reading just over 1/4 full, where with the original alternator it'd be reading closer to where that gauge does in the photo. (and it'll take 18 gallons to top it off).

Reserve light can also be affected by the attitude of the car. When the tank just starts to get low on mine, reserve warning will light up nose-down on a slope or under braking, and go back out when the car is level.

Used to have to pay quite close attention to the gas gauge when the car would get 6-8 MPG in town with CIS...

[PeteKz]

+3 on the gas can. Until you know from your own experience at what point the low light comes on, carry one. Or find out the hard way. Is your AAA paid up? Do you feel lucky?

[Old H2S]

Everything said above is true. But it is your new car and YOU do not know and that information is good to have. So bring a can and drive it around until the light comes on , then go fill it up and see how much it takes. I do like the drain the tank with the big bolt on the bottom and spray out all the crud..it is an unknown car to you and do the filling until the light goes out.

[SpyderMike]

The low light comes on when the sensor float touches and connects two contacts at the very bottom of the sender. That is the light's circuit path.

[motorstereo]

I keep one of these with my 5 gal gas can, the flexible section makes pouring gas in much easier. And use non-ethanol gas if you can find it!

[jgurnari]

no problem. it’s still above the line… if you see the light flashing as you drive due to gas swishing around, you still have 30 miles

[Schulisco]

Fun fact: I filled up the 911 last weekend, tank gauge showed up less than 1/4 full of gas, but no reserve light. At the end 20litres / 5,3gallons were still in the tank so I could add 60litres / 16gal. The lower the fuel gauge displays the more unprecise it gets.