Fuel Gauge never reads full - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Overdrive · 09-03-2010, 09:25 AM

Hey, everyone. This is an issue I noticed right off the bat with my '97. When I first got it I went about filling the tank, as it was reading between 1/4 and empty. I let the pump work until it shut itself off, and this was so long ago that I can't recall how many gallons I did actually pump, but the point being when I got back in the car and fired it up, the fuel gauge only came up to just about halfway between 3/4 and full.

So far I've filled the tank twice, and the gauge still only goes as high as that with no noticeable improvement. It does take a decent amount of miles before it moves from that indicated spot, but it has never read full for me, so to be safe I have never let the gauge go below 1/4 again, as I can't trust the gauge. Now the car did sit at the place I purchased it from for about 5 years or so and was probably only started to move it from one space to another on the lot during that time, possibly the occasional test drive of any interested folks, and probably also had that low level of fuel in it for that long period of time, but my wonder is whether this is a problem of 14 years of age and the gauge just not reading as well as it did back in 1997, or if there could be a different problem? Finally, is there some way of adjusting/re-calibrating the gauge so that it will read full when the tank is indeed full? If there's any other information on the matter that anyone needs I'll do my best to provide that for you. Thanks for any help, insight, and/or advice provided, everyone.

eightsandaces · 09-03-2010, 09:57 AM

I'll bet it's a stuck tank float, since the Boxster has a low gas light, I wouldn't worry about it unless it bugs you. It's likely an expensive repair for little return.

Overdrive · 09-03-2010, 02:29 PM

Quote:

Originally Posted by eightsandaces

I'll bet it's a stuck tank float, since the Boxster has a low gas light, I wouldn't worry about it unless it bugs you. It's likely an expensive repair for little return.

It is annoying, eightsandaces, since I like to have my vehicles in as good repair as possible, though it is someting that I can live with...overall the only time it'll really bug me is when I fill up.

And I figure you're rigt as far as it being a fix that'll probably be more of a cost than it may be worth, but I figured I'd ask around here and see if it's actually easier and less costly than I think. The gauge seems to operate normally other than not reading full when the tank actually is, though I haven't driven to the point of getting a low fuel light, so I may have to check on that part of its functiion, as well.

eightsandaces · 09-03-2010, 03:21 PM

Quote:

Originally Posted by Overdrive

It is annoying, eightsandaces, since I like to have my vehicles in as good repair as possible, though it is someting that I can live with...overall the only time it'll really bug me is when I fill up.

And I figure you're rigt as far as it being a fix that'll probably be more of a cost than it may be worth, but I figured I'd ask around here and see if it's actually easier and less costly than I think. The gauge seems to operate normally other than not reading full when the tank actually is, though I haven't driven to the point of getting a low fuel light, so I may have to check on that part of its functiion, as well.

OD, I'm with you on making the cars as perfect as possible, working on gas tanks is a pita. There is a chance you can replace the float mechanism without tank removal or even free up the unit you have. I've never studied that part of Bentley. I certainly wasn't suggesting you let the vehicle fall into disrepair, just letting you know gas tanks suck. Since I run half tank to save weight, it would never bother me...

PS If you run it to the near empty, then fill it up you might just get lucky and get the float working again, it's not without precedent.

ekam · 09-03-2010, 04:57 PM

I know a friend broke his Mercedes ML tank gauge by keep holding the gas pump release after it clicked a few times until it's completely full. If you hear the click and the pump releases itself you're supposed to stop pumping, but he didn't thinking he will get more into the tank.

Overdrive · 09-03-2010, 11:01 PM

Quote:

Originally Posted by eightsandaces

OD, I'm with you on making the cars as perfect as possible, working on gas tanks is a pita. There is a chance you can replace the float mechanism without tank removal or even free up the unit you have. I've never studied that part of Bentley. I certainly wasn't suggesting you let the vehicle fall into disrepair, just letting you know gas tanks suck. Since I run half tank to save weight, it would never bother me...

PS If you run it to the near empty, then fill it up you might just get lucky and get the float working again, it's not without precedent.

I didn't take your words to mean that at all, eights.

I know what you were getting at. Like I said, it's just a pet peeve of mine when it comes to my cars not being in tip-top, and I know I've got a long road ahead of me before I get this Boxster to where I'm quite happy with its overall condition. It's those little things, like a fuel gauge being a little off, that seem to bug me worse than if part of the car's body were hanging off, heheh.

Despite it being a little thing, though, working on it isn't as small of an undertaking, so like you said, little return for the effort.

You make a good point, though. Maybe I will run the tank down on a long drive or something, and see if filling it up from there will smack some sense into the float.

vath2001 · 09-04-2010, 02:39 AM

My indicator gage works ok, but I do notice that the level drops very quick from the full to the half mark... and that's not from my driving habit either. After that it does take a while to finish the second half of the gage.

j.fro · 09-04-2010, 07:58 AM

There was a technical service bulletin on this for some models. The float arm would get tangled in some of the wiring, and the TSB basically says to zip tie the wires out of the way. The float mechanism isn't too tough to get to; the job can be easily accomplished in a couple of hours. I'd suggest driving the car to almost empty before tackling it, just to minimize the amount of fuel you have to work around.
Be careful undoing the snap-connect fittings from the plastic nozzles on the top of the fuel sending unit...the nozzles can become brittle.

eightsandaces · 09-04-2010, 08:37 AM

Quote:

Originally Posted by j.fro

There was a technical service bulletin on this for some models. The float arm would get tangled in some of the wiring, and the TSB basically says to zip tie the wires out of the way. The float mechanism isn't too tough to get to; the job can be easily accomplished in a couple of hours. I'd suggest driving the car to almost empty before tackling it, just to minimize the amount of fuel you have to work around.
Be careful undoing the snap-connect fittings from the plastic nozzles on the top of the fuel sending unit...the nozzles can become brittle.

Good advise on draining the tank, remember, gas vapors are volatile and incredibly flammable. Work in a ventilated area and be conscience of any open flame, including a hot water tank pilot, avoid anything that could cause even the weakest spark.