3/4 is as full as it gets! - 986 Forum - The Community for Porsche Boxster & Cayman Owners

RandallNeighbour · 12-05-2005, 05:10 PM

I've got a puzzling question to pose to all you intelligent boxster DIY guys out there...

My boxster never reads 4/4 when I fill up. The best I get is a hair over 3/4 full.

I replaced the instrument cluster with a brand new one (needed it anyway for a burned out LED segment). Didn't fix the fuel indicator.

Hans (mechanic) tied off the fuel lines inside the tank to keep them from getting in the way of the sending unit's float switch. Didn't fix the fuel indicator.

I replaced the fuel sending unit and calibrated the unit. Didn't fix the fuel indicator.

What else could be causing it?

donv · 12-05-2005, 06:03 PM

These may be so very old school (not high tech), but did you test to see whether the correct voltage into the fuel gage produces a "full" reading (sounds like you tested the sender, but not the "receiver" (gauge)? Could there be a bug (literally) somewhere physically blocking the needle at the gauge itself?

deliriousga · 12-05-2005, 07:21 PM

Willkommen an Porsche.

You've found the one item that seems to be unworthy of repair. Most 928s only show 3/4 at full and everyone says it's not worth fixing because the new one will do the same in a few years.

Look at the bright side. You'll never run out of gas with a 4-6 gallon reserve. :dance:

SD987 · 12-05-2005, 07:32 PM

My BMW does this if you don't remove the key from the ignition before filling it up (leaving it in while filling)...so I'm in the habit of removing the key before pumping gas into whatever I'm driving. Do you?

12-06-2005, 12:35 PM

Quote:

Originally Posted by RandallNeighbour

I replaced the fuel sending unit and calibrated the unit. Didn't fix the fuel indicator.

What else could be causing it?

Randall, you say that it was calibrated. Are you sure it was calibrated correctly? I remember reading somewhere that the calibration process is fairly complex (drain tank, add a pre-set amount, calibrate...).

I can't find the article/posting. If I find it, I'll resend it to your attention.

RandallNeighbour · 12-06-2005, 12:37 PM

Yeah, I remove the key all the time and it still does it, and Hans and I drained the tank and filled it one cup of fuel at a time to calibrate it with the PST tool attached... It was a real pain in the butt. He does it all the time at the dealership and it's routine for him. He was puzzled as well as to why it does not work.

Doggonit, I drive one of the most dreamed about cars on the planet!!! I want my fuel indicator thingy to work right!

How about prying off the needle and moving it up? My mechanic says the empty idiot light that comes on when you're running low on fuel is not triggered by the needle, but by an electronic sensor.

deliriousga · 12-06-2005, 01:41 PM

Quote:

Originally Posted by RandallNeighbour

How about prying off the needle and moving it up? My mechanic says the empty idiot light that comes on when you're running low on fuel is not triggered by the needle, but by an electronic sensor.

Yep. I've never seen the idiot light on the 928. It would hit empty and I would fill it with 16 gallons. The needle was all the way down, but no light. Then I read the manual and saw it holds 23 gallons. As you said, "I drive one of the greatest cars ever made so why doesn't the darn gas guage work right?"

12-06-2005, 06:40 PM

I found the post I was thinking about. Here it is:

"Should the car still be under warranty I would suggest that you bring it to your closest Dealer. The malfunction that you describe may be as simple as just recalibrating the fuel level sensor. While this is simple for the Dealer or any Independent shop with a PIWIS or System2 tester it is not for the owner. There is a specific amount of fuel that is to be in the fuel tank for the calibration and the requirement of the tester. To have the proper amount of fuel in the tank requires the draining of it and then the adding of this specific amount. Even should the car require a new fuel level sender it would still require this calibration.

Scott Slauson - PCA WebSite - 11/23/2005"

Rail26 · 12-06-2005, 07:04 PM

Randall...does it really matter? I know you like to live on the edge, but something tells me you wouldn't drive to the empty light anyway. Houston has a gas station every 100 yds so you are safe. By the time you re-build that 986...you would be halfway to owning a 987. Want to buy mine?

RandallNeighbour · 12-07-2005, 07:04 AM

Rail, you have a good point... but I do not forsee having another sizeable wad of cash to buy a newer boxster for a long, long time. So I'm just fixing up this old one for the duration. I no longer finance automobiles, so it's cash up front or no buy.

I'm quite anal about maintaining everything I own, and having a Porsche in the garage that can't indicate a full tank of gas when every single other car I've owned, including some really crappy ones, have fuel gauges that work fine just drives me nuts.

I'm not losing sleep over it, but you know, there's "right" and then there's everything else.

Rail26 · 12-07-2005, 07:45 PM

Randall-nator,

Were you a hallway monitor in high school?

By the way, please keep me informed if you get the Houston-Austin drive together. I lived in Austin for a while and would love to drive in for it.

RandallNeighbour · 12-08-2005, 08:31 AM

I did not develop picky tendencies until I was in my 20's. I did get busted by hall monitors in grade school from time to time though if that helps any!