ogm

I noticed when driving my 964 today that the fuel gauge showed empty tank and the fuel warning light was blinking on and off. There was no central warning light as usual if the tank is near empty. I know the tank is 3/4 full.
Any ideas?

Odd Gunnar Moe
Norway

Indycam

Just for grins , pull the wires away from the sender atop the fuel tank and see what the gauge does .


Arctic Circle, Norway ???????????

ogm

I pretty sure I tried that yesterday, giving the same readings with the sender unit unplugged.

Smokin

ogm... Just take out the sending unit and clean it all up. If you do a search you will find a few threads on the subject. Sometimes all they need is a cleaning. A lot of dirt gets in there over the years.

The float (sending unit sensor) rides up and down on two wires. If the wires are dirty you get no signal or at least intermittent signal. I think in one case someone's wire had snapped. They replaced it with a wire out of a piece of cabling and it worked well.

Good luck and please post back what the fix is!

Indycam

"same readings with the sender unit unplugged"
I would say do a few tests before you start taking things apart .
What ever you do be very carefull , gas and sparks = a bad time .
The sender is a variable resistor , its resistance goes up and down with the gas .
If you have a multi meter you should be able to watch the resistance change as the tanks filled .

If you have a decade box or know someone with one you can hook it up in place of the sender a spin it up and down to see if the gauge / wires to the gauge are ok .

If you don't have , can't find a decade box , a ten turn VR can do the same thing if speced ok .
What ever you do be very carefull , gas and sparks = a bad time .
Another way to test is to go from open to zero resistance and see if the neddle swings from peg to peg .

I have never done this test on a 964 , so I don't have details on readings .

ogm

Measured the resistance on the sender unit yesterday. I have read that i should vary from 75 ohm with empty tank to approx 10ohm with full tank. Mine read open circuit , so i guess the wire is broken. If the resistance is up to 75 ohm in the wire, it can not be replaced with a wire out of a normal cable. I will have drive some more miles to lower the fuel level and take out the sending unit for inspection.
I will come back with more information.

Thanx guys

Odd Gunnar Moe

Smokin

ogm... I think the reason for the differences in resistance is because of the sending unit or float that rides up and down the wires... Not the wire itself.

In my case the fuel gauge worked but I was getting a flashing light saying "low fuel" yet it was not kicking on the ! master. When I took out my sending unit it was filthy. After cleaning it up it worked perfectly. Now... After using my car a lot more often I never see the fuel warning unless I am low on fuel. About a year ago someone posted how they replaced their wire.

Just searched... Here it is....

Click me! Fuel Sending Unit Fix

ogm

I have also read that tread. Im an engineer in electronics. A Cu-wire like in your telephone cable have a resistance of approx 0,065 ohm pr. meter/yard. As i have understood the wire in the sending unit is of a high-resistance type and the unit is calibrated to the specific wire used?

I will check this this weekend and reply.

Odd Gunnar Moe

Indycam

Why is a electronics engineer asking for help ?

Miguel

and even more when he resides in the artic circle?

Smokin

Would YOU want to run out of gas in the Arctic Circle???

ogm... Trust me... Take it apart and you'll see what I mean.

ogm

Guys, i wasnt trying to be rude saying im an electronics engineer (the Porsche electronics is complicated for me to), I just had some doubts about replacing the wire with one from a cable or speaker as the resistance should be totally different.
Anyway i took out the sending unit today. The end cap had come of and is at the bottom of my gas-tank. The aluminium-tube is also at the bottom of the tank, and the wire is broken/destroyed. Ripped of the wire, measured the resistance to 75 ohm. Therefore I will have to order a new unit. I will leave the tube and cap in the tank so far, and will remove the tank later to get the remains out of there.


Regards
Odd Gunnar Moe
Arctic Circle
Norway

Indycam

http://www.aventools.com/admin/uploa...blePick-Up.jpg
http://cgi.ebay.com/24-Claw-Pickup-P...QQcmdZViewItem

jimq

that sure looks like a pretty place to run out of gas! Would want to have some warm clothes handy tho

ogm

Picture taken at my local racetrack, Arctic Circle Raceway 2 weeks ago.
The northernmost racetrack in the world 2.35 miles long and brilliant!
Located where it is, the season is only May to October. In the winter there could be up to 3 yards of snow on the track.

Thanks to the Gulf-stream our climate is probably like Canada, not like the north pole.....
Anyway a C4 does the job with winter-tires fitted. We normally use studded winter tires but the Porsche have unstudded winter tires. Works pretty good on snow but a bit scary on ice.

Indycam, the tools seems proper for the job.

Odd Gunnar Moe