Fuel gauge never goes beyond 3/4

[GromitInWA]

I have a new fuel sender and it was replaced with an almost empty tank. Since then, the fuel gauge no longer reads full. I've read threads about calibration, zip ties on the lines and also the vent line preventing the tank from filling. However, I filled the tank up to overflowing and then drove it until the refuel light came on. Thinking that I actually had 1/4 tank plus the 1/8 reserve left, I drove it some more and calculated that I should have had about 4 gallons left when I took it to my Indy for calibration. They drained the tank and found just about fumes (less than a gallon) then they filled to 13 liters and did the calibration. I then filled up to the gills again and the gauge reads 3/4 or a little and rises slightly but never to full. As stated before, the gauge used to work.

From the observed behavior, it seems that the tank is filling to full and the gauge is not reading off (since when the gauge was reading empty the tank really was). The only other piece of information is that I have pulled the instrument cluster to fish a Bluetooth microphone to the factory spot, but everything has been reconnected and other gauges appear to work.

So what are your thoughts... Defective replacement fuel sender or something else?

[JFP in PA]

I have a new fuel sender and it was replaced with an almost empty tank. Since then, the fuel gauge no longer reads full. I've read threads about calibration, zip ties on the lines and also the vent line preventing the tank from filling. However, I filled the tank up to overflowing and then drove it until the refuel light came on. Thinking that I actually had 1/4 tank plus the 1/8 reserve left, I drove it some more and calculated that I should have had about 4 gallons left when I took it to my Indy for calibration. They drained the tank and found just about fumes (less than a gallon) then they filled to 13 liters and did the calibration. I then filled up to the gills again and the gauge reads 3/4 or a little and rises slightly but never to full. As stated before, the gauge used to work.

From the observed behavior, it seems that the tank is filling to full and the gauge is not reading off (since when the gauge was reading empty the tank really was). The only other piece of information is that I have pulled the instrument cluster to fish a Bluetooth microphone to the factory spot, but everything has been reconnected and other gauges appear to work.

So what are your thoughts... Defective replacement fuel sender or something else?

The factory calibration procedure is to use 28 liters (7.3 US gallons), not 13 liters. It is also important that the fuel tank is completely empty before starting this procedure.

"Calibrating fuel level sensor system

1. Disconnect the battery and cover terminal or battery.

2. Remove cap over the fuel level sensor system.

3. Remove fuel level sensor. Removing and installing fuel pump.

4. Using a fuel extractor, completely drain the fuel tank through the fuel level sensor opening.

5. Make sure that the two recesses on the left and right hand sides of the tank are emptied completely.

6. Reinstall the fuel level sensor and, with "ignition off", fill the tank with exactly 28 liters of fuel.

7. Perform tank calibration with the Porsche System Tester 2 (PIWIS or Durametric):

- Select vehicle type (911 Carrera)

- Select control modules

- Select instrument cluster

- Select menu item "Tank calibration"

- Confirm calibration

8. The fuel level sensor system has now been calibrated."

[GromitInWA]

Thanks JFP. I might be mistaken about the 13 litres though I think it is what the diagnostic tool (Autologic) suggested. One question: the recesses mentioned above make me wonder if those instructions are for a C4?

[JFP in PA]

Thanks JFP. I might be mistaken about the 13 litres though I think it is what the diagnostic tool (Autologic) suggested. One question: the recesses mentioned above make me wonder if those instructions are for a C4?

It is also for the C2, you just have to be more careful with the C4 because there is more places for residual fuel to hide due to the unusual tank shape. Plus the two tanks are close enough in capacity (the manual says 16.9 gallons for the C2, 16.6 for the C4) that there should be no real difference. 28 liters is the correct fuel quantity, and you also should not be using anything other than a Porsche specific diagnostic tool to do this, we have had to redo several that were supposedly done correctly with another system, only to have problems. Done correctly, the cars were fine.

[Loren]

Just to clarify fuel tank calibration amounts (per the service manual) --

C2 = 12 liters

C4 = 28 liters

[GromitInWA]

... you also should not be using anything other than a Porsche specific diagnostic tool to do this, we have had to redo several that were supposedly done correctly with another system, only to have problems. Done correctly, the cars were fine.

So a PST2 or PIWIS and not the Autologic system that my indy uses?

[JFP in PA]

Just to clarify fuel tank calibration amounts (per the service manual) --

C2 = 12 liters

C4 = 28 liters

I stand corrected. Further research had demonstrated that Loren's information is correct, and I should also note for future reference that multiple information sources, including Bentley's 996 manual, have proved to be incorrect on this point. The publisher has been notified of the correct information.

[JFP in PA]

... you also should not be using anything other than a Porsche specific diagnostic tool to do this, we have had to redo several that were supposedly done correctly with another system, only to have problems. Done correctly, the cars were fine.

So a PST2 or PIWIS and not the Autologic system that my indy uses?

It is impossible for me to know if the tool your indie use is accurate or not, but based upon our experience with the results of some other highly considered diagnostic tools which were supposed to be able to do this calibration and did not, I would suggest caution on how the calibration is done. The PST II, PIWIS, and Durametric a known to be able to do it, other systems not so much.

What is known is that your tank was not completely empty before running the test, and from your memory they added 13L of fuel, which would appear to indicate that there may have been more fuel in the system than should have been for the calibration, and which may have thrown it off. I'd suggest that your indie rerun the calibration with the tank completely dry, 12L of fuel, and their Autologic tool; the outcome should answer your question.

[GromitInWA]

Yes. I'll have a chat with them to see what they did.

[01slvr996]

On 4/13/2014 at 4:39 PM, Loren said:

Just to clarify fuel tank calibration amounts (per the service manual) --

C2 = 12 liters

C4 = 28 liters

I replaced my fuel pump in my 01 C2 and now my gauge never reads full, only 3/4. Just want to confirm for my car it is 12 liters; and nothing has changed in the last 4 years.

[Loren]

16 minutes ago, 01slvr996 said:

I replaced my fuel pump in my 01 C2 and now my gauge never reads full, only 3/4. Just want to confirm for my car it is 12 liters; and nothing has changed in the last 4 years.

 

Correct no change to tank calibration amounts.

You empty the gas tank - then add 12 liters and use a PST2 or PIWIS to run the calibration. 

[James Austin]

Is the calibration for a 06-08 Cayman different??  Thanks for a reply.

[Loren]

2 hours ago, James Austin said:

Is the calibration for a 06-08 Cayman different??  Thanks for a reply.

 

No, for the 06-08 Cayman...

You empty the gas tank - then add 13 liters and use a PIWIS to run the calibration. 

[Boris1]

I want to do the calibration but don't understand how to do it in durametric. I have the enthusiast version, but when I go to the cluster module I don't see an option for fuel tank calibration. I have an option to turn on various lights and sounds on the cluster or to reset the cluster (I don't know what a reset means), but no option for fuel tank calibration. Has someone done it with durametric, and if so, how?

[JFP in PA]

Not sure the enthusiast version can do this; you might want to contact Durametric directly and ask. 

[Boris1]

So I just wanted to provide an update here. I reached out to Durametric and they said none of their versions (pro or enthusiast) has this function and there are no plans to add it either in future updates. I am disappointed. I thought the durametric would be all I need, but now I have to find some other option. If I was going to buy a PIWIS or something else in that price range, why do I need a durametric? Anyhow, does anyone know if there are other scan tools out there (Autel, Foxwell, etc.) that may have this functionality? I emptied my tank completely and was ready to do this calibration by the book only to be dissapointed by durametric.

[Loren]

Any shop that has an old PST2 should be able to help. More available than PIWIS and they may even loan you the PST2.