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Used Porsche Cars for sale in Slough, Berkshire | RSJ Sports Cars

Fuel Gauge not registering small top-ups

W

Whytar

Hockenheim
Joined
3 Jan 2015
Messages
661
Just wondering if anyone else has had a similar experience... If I let my fuel drop into the 'red' zone then fill up with just 10 or 15 pounds worth of fuel I notice that the fuel gauge doesn't register it and the range says it's the same as before the top-up.

It seems to only like larger (half or full tank) fill-ups...

Anyone else had this issue?
 
4wd has saddle tanks, the float is above the point the tank divides

So they all do that
 
Learn something new every day on here

:yes:
 
More information on the 911 fuel tank here
 
Thank you. That makes a lot of sense and puts my concern at ease...
 
Porsche did it to shame people into brimming their tank when they refuel :grin:


edit: It does actually explain all this in your handbook.
 
markiii said:
4wd has saddle tanks, the float is above the point the tank divides

So they all do that
Click to expand...

The saddle design of the (lower) tank is not the issue.

The issue is the upper and lower segmentation! (the somewhat convoluted constriction between them)

The small lower tank cannot support the use of a contiguous float or capillary sensor all the way to the base (ie it only operates in the larger upper tank).

The lower tank use is estimated by the DME (using fuel injection volumes), but it cannot know if you then added a small amount (<19L total) of fuel.



99620102201lr.jpg
 
Mine doesn't register until I put a lot more than 19 litres in (more like 25) which may explain my faulty fuel gauge and diagnose is a mechanical fault (ie. float sensor) and not a software fault.
 
Do you know if your car has ever had the upgraded recall part?

TSB R2000.14 Kraftstoffkugelhahn (fuel ballcock update)

http://www.directwatertanks.co.uk/image/cache/data/ball-*****/images-500x500.jpg








... in all seriousness, there was a DME update that corrected early C4/Turbo fuel gauge readings


15/01 DEC 01 Instrument Cluster - Incorrect Fuel Level reading


You should also be aware loss of battery power in certain circumstances can require re-calibration of the fuel gauge datums.

(on my VW it was overly optimistic with the gauge and thus range to empty etc, so I used VAGCOM to change the correction factor in the DME just for this purpose: apparently the expectation is that the sensors are variable in their output, so they are able to be set individually)
 
Cheers GT4. I contacted the OPC Byfleet Service Centre when I bought my car after reading the post in this sub forum for any outstanding recalls. They told me my car didn't have any????? So I'm not 100% sure, I can only go off what they said.
:dont know:

I've disconnected my battery numerous times with the tank full, empty, half full, etc. to see if I can get any variation of the gauge reading but it's repeatable, no matter what I do. I've worked it out and (almost exactly) I've 18.2 litres in the tank (4 gallon) when the light comes on. I've run out twice and predicted both times within a couple hundred yards.

I've lived with it but it is rather irksome. Nothing more annoying than the light being on and it only taking £50 to brim it. Feels like your either tied to the pump or driving round like a chep b4stard with the light on.
 
:yes:

:nooo:
 
I suppose I could fill the bottom of the tank with 2 gallon of resin :lol:

Apologies for the :hijack:
 
Won't help

The issue is with the sensor or its calibration, not the tank shape.
 
@Alex- is the gauge consistent, i.e if you fill when its showing 3/4 full, is it about right?

This might give you a steer as to whether its the float, or the DME calibration that's at fault. The car clearly thinks its using more fuel than it actually is- is the OBC MPG really low vs 'brim to brim' calculation?
 
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