mambodoc

So far my new C4S launch Coupe is a blast. I'm only at 1,200mi and ran the tank into the "reserve" zone...was rushing to get to work last night...and when I went to gas up this a.m. afterhaving purchased 5 gallons, the fuel gauge remained unchanged to the degree of counting down the remaining miles to zero....(10 mi drive home). The car sat all day and this p.m. I filled it up...the total gallons jived with tank capacity. Initially the guage showed 3/4 full and within 5 minutes of driving, worked its way up to full. Any ideas or experience with this? It is an 8/08 build and I purchased it 2 weeks ago with 34 mi on the odo. I'd like to trust the gauge/s...all of them. This is my 4th fill up I believe. Thanks!

Fahrer

Did you turn the ignition switch on while the car was being filled? I experienced this with another car and it took a while ( driving for about 15 minutes) before the gauge reached ( showed) full.

mstams

This happened to me once before. Coincidentally, I also have an early build (10/08) ordered C4S coupe. I partially filled the tank with just a few gallons after driving to almost empty in an unfamiliar part of town. To my surprise, the gauge acted like I had added no fuel at all -- still showing only a few miles left in the remaining range. It made me wonder if there was a problem with the pump, but I drove back to my usual fill-up station near my house on the other side of town and was only able to add the expected remaining balance. The gauge seemed to hesitate at less than full but then went all the way up to full mark.

Like I said, that only happened once. I now have over 6,000 miles and have never let it get that low again. Not sure if it was just a fluke, but I wouldn't worry too much about it.

mambodoc

The ignition was not touched Farher. The scenario was exactly as experienced by mstams. We'll see what happens. Will probably run it low again to check it...if repeats...back to the dealer. Thanks for the input. Anyone else?

simsgw

Well, for what it's worth, the current owners manual (2009 that is) says the gauge and the "miles to empty" indication will not be correct after a partial fill. I can go get the exact wording if it matters, but I think it amounts to "Don't do that." Partial fills, that is. Or at least do your range calculations in your head if you do.

Edgy01

Partial fills confuse the system. Try to avoid doing that.

mambodoc

Thanks guys, I guess I should read the manual. That said...any hints to programming the homelink garage door opener. My opener has a rolling code and I DID read the manual on this but still no go. Anyone?

vexed

I followed the instructions in the manual and it worked the first time. I did stand directly in front of the car and pointed the remote at the bumper. Give it another shot, it should take.

MyEmily

There where a discussion on Homelink. The best way is to go to homelink.com and follow their instructions. It's slightly better than the porsche's instruction.

mambodoc

Will do. Thanks!

Minok

Ok, so today I had my experience with the dumb gas level gauge.

Drove the car to about 42miles remaining, needle a bit into the lit-up-orange last 1/4 tank region (the message about fuel already cleared). Drove into a convenient but expensive station to get a splash of fuel.

I added about 3.4 gallons. Drove off. The remaining miles and the fuel level needle actually went DOWN. Now I was reading 35 miles left, and the needle was further down in the last 1/4 tank than before.

Hey, I can understand that miles remaining might be thrown off a bit.. maybe.. but why the heck is the needle not reading the right tank level? Why did my 94 VW Golf have a better fuel capacity system than my Porsche 997.2?

I can only conclude that these cars actually have NO WAY of measuring the fuel level in the tank as it goes up and down at all. They must only have a way of sensing that you have filled the tank, which resets the system to full and then have a flow meter that measures fuel leaving the tank so that they compute the remaining capacity and miles based on the fuel you have consumed. That would jive with the idea that the system is inaccurate on a partial fill that supposedly is in the manual.

So, the fuel guage ONLY measures how much fuel you have used since the last FILL UP (or near fill up). Once it gets below a certain point, the car doesn't recognize you have put more fuel in the tank. Methinks thats a bit crazy-stupid, but if the tank shape is really wierd, thats probably the best solution, since metering the actual tank level would be a nightmare.

But it was still a WTF moment to put 3 gallons in and see no improvement on the needle. Very odd feeling.

YA911Fan

If they can't measure the fuel level correctly after all these years, it makes you wonder why they think they can accurately measure the oil level.

Mike in CA

I can't explain what you noticed, short of some kind of fault, but I've had a different experience. Recently I was down to about 1/4 tank. I don't run autoX with a full tank to save weight, so for my upcoming event I added a couple of gallons of Sunoco 100 at home. The fuel gauge went up in response. To top up to about 1/2 tank I stopped at the gas station and added another 3 gallons. The gauge went up again to the appropriate level. Seems to me if what you are saying about how the fuel level is measured were true, the gauge would have been totally confused and not responded as it did.

RED HORSE

I had the same problem. Homelink folks said I needed a new battery in my opener. I told them the opener worked fine. After trying several times without success I went ahead and changed the battery in the hand held opener and the process worked as outlined in my owner's manual. Try changing the batteries.

Fahrer

All cars basically use the same design for fuel sending units. A float is used to determie fuel level ( nothing elaborate as described in your post). There have been problems over the years with sending units ( often European cars) exposed to the higher sulpher levels in fuels used in the US. The sulpher would react with the additives in the fuel to form deposits on the metal contacts in the sending unit, resulting in faulty readings. I had a 1999 Audi A6 with this problem. They replaced the sending unit four times... but all with same design of course. The problem was never really fixed. Imagine the problems with Quatro models which used THREE sending units per car ( in series)! I had a 1986 Taurus with the same problem. It was a common problem with those Fords also. You may want to try a different brand of fuel also. Also, do not turn the ignition key to "on" while the car is being filled. It might take 30 minutes after starting to read properly.