Aaron Posted August 19, 2017 Author Share Posted August 19, 2017 I'll be getting at it myself soon and testing it. It can't be that difficult to move the float manually and see if it hits full. I called Porsche Bristol to get a second opinion and they said that the diagnostic offered was a likely culprit. Link to comment Share on other sites More sharing options...
Aaron Posted August 22, 2017 Author Share Posted August 22, 2017 Picked up a fuel sender for £90 direct from Porsche. That beats the hell out of Cardiff's £200 for the part. I'm gonna rent a garage when it arrives and swap it over myself. Update to follow once that's been done. I'll try to get some pics and share my testing methodology as this issue seems to be prominent in the community but there's little info besides dealers resolving the issue. Link to comment Share on other sites More sharing options...
tomprout Posted August 22, 2017 Share Posted August 22, 2017 The problem that you may face is the need to calibrate this new sensor... Don't you think? Link to comment Share on other sites More sharing options...
Aaron Posted August 22, 2017 Author Share Posted August 22, 2017 Technically speaking, all of the senders should give the same level of resistance range and should, therefore, all be within the same margins. Provided the current calibration is accurate (which, according to Cardiff, it was), then replacing the sender should resolve the issue without any calibration provided the sender is actually what's at fault. Link to comment Share on other sites More sharing options...
Aaron Posted August 27, 2017 Author Share Posted August 27, 2017 (edited) I have an update! A friend and I removed the fuel sender from the tank and tested it with it outside of the tank, moving the float up and down. Initially, it looked like the sender was buggered as the gauge was stuck in the same place as before. However, I noticed a bit of gunk/dust at the top of the sender gauge, cleared it off and it now read full! Tested empty and full a couple of times and I've now got more fuel in the car than before I started! Going to fill it up later but I'm confident the issue is now resolved. This is the top of the fuel sender unit and you have to remove this lock ring to get into the tank and see the sender's internals: Once you're past the lock ring and initial connections, you partially lift out the sender, wiggle it around until you can get your hands on the fuel pump connector hose. Remove this and the plastic clamp holding on the two spade connections then fully lift the sender out. I would recommend tying the fuel pump outlet hose to something, otherwise it will drop into the tank and you have to fish it out (I tied it to be safe). I then remotely wired the battery (only low load so the wire was fine), turned on the ignition and began moving the float. Testing the gauge, moving the float up and down: The sender went back in fully assembled, lock ring back on, tray loosely on top, start car and smell/check for leaks. Car started fine and let it run for a bit - no leaks. Remove the battery tray, visually inspect it and, again, no leaks. Tray back in, battery back in, terminals connected and cover back on. It's been an hour and a half job with plenty of breaks as it's simply scorching hot today! I'm going to fill up sometime tomorrow and I'll inform everyone of the outcome. It should go full... Edited August 27, 2017 by Aaron 1 Link to comment Share on other sites More sharing options...
barryb Posted August 27, 2017 Share Posted August 27, 2017 Hi Aaron Well done, you need a job in a Porsche garage specialising in fuel gauges Barry Link to comment Share on other sites More sharing options...
Aaron Posted August 27, 2017 Author Share Posted August 27, 2017 Cheers, Barry. This isn't my first fuel gauge rodeo, fortunately. There seems to be so little info in the wild about this. I think the majority of Porsche owners must bend over for dealers/specialists and take little into their own hands. Or, they do, and they just don't bother to tell anyone about it! Link to comment Share on other sites More sharing options...
Aaron Posted August 28, 2017 Author Share Posted August 28, 2017 (edited) I filled up today and no joy... s**t. It actually sat lower with a full tank than where it was previously. It did make its way back to where it has been sitting eventually, however, so something is amiss with the sender. It worked when it was outside of the tank, but I was leaning the contacts directly onto the PCB rather than freely floating. This leads me to think the contacts are worn. The crud that was on it has probably not helped. My replacement gauge should help me here - it's actually from a gen 1 997 911 (brand new) but the sensor in the fuel sender is still a Siemens VDO A2C53104913. Lever at the lowest level (empty) gave resistance of 300 ohms and at the highest point (full) was 10 ohms. The sensor is mounted upside down in the sender. I'm going to compare the resistance values against the unit on the car and swap them over tomorrow. Whilst the gen 1/2 fuel sender units themselves are not the same (plastic apparatus is rather different), it does appear that the sensor itself is the same and swaps in and out. Yes, I could've measured the resistance previously but I had no control numbers to know whether they were actually within spec or not. Now I do. Only real hassle swapping them is that there's a plastic connector on the gen 1/997/987 sender and the gen 2 is soldered directly to the terminals for the connector. I'll be getting the sender out tomorrow (again) and soldering the new one into place. Haven't whipped the iron out in a while; this should be fun. I'll take pictures for reference. I am not paying £400 to a dealer to resolve this issue. Edited August 28, 2017 by Aaron 1 Link to comment Share on other sites More sharing options...
Aaron Posted August 29, 2017 Author Share Posted August 29, 2017 Swapped the sensor today. It did work like I thought it would, so that's good. I have lots of pictures to describe the process but I'm on my phone and photos are a big hassle. I'll edit/post another update. The gauge looks like it's pretty much in the same place so I'm starting to question the calibration. Swings and roundabouts... Link to comment Share on other sites More sharing options...
Aaron Posted August 29, 2017 Author Share Posted August 29, 2017 (edited) OK, so this is the story. Bought a sender from a 997 gen 1 which has a different sender apparatus but the Siemens VDO potentiometer and float are identical. The sensor can be removed from the apparatus quite easily. You can see the disassembled parts as follows: Pretty obvious, really. The contacts run along the circuit board and vary in resistance - the lever is raised and lowered by floating in the fuel tank thus adjusting the resistance. Now the numbers. The sensor is mounted upside down on the sender so empty is a high value and full is a low value. Old sender: Full: 10 ohms Empty: 300 ohms New sender: Full: 10 ohms Empty: 300 ohms The only difference between the two was that the newer float was much easier to move by hand that I can observe. The resistance values are the same. I then measured the resistance present when the tank was full (to the point that fuel is tipping the filler neck) and the value was 30 ohms. This would suggest that the sender cannot hit 10 ohms in the 54 lite tank but I imagine it would in the 64 litre. Instrument cluster, after said fuel brimming, shows the following: The car decides that, based on the amount of fuel it thinks is in the tank it could do 298 miles at 23.9 MPG. This works out at 56.6 litres of fuel which would align to the "overfilling" of my 54 litre tank. It has to be the fuel tank setting/instrument calibration. There is simply no other explanation. The new sensor connected to my gen 2 sender unit: I'm calling Porsche tomorrow. This is getting ridiculous. Edited August 29, 2017 by Aaron Link to comment Share on other sites More sharing options...
tomprout Posted August 30, 2017 Share Posted August 30, 2017 Hi Aaron, We definitely have the same issue... Anyway thanks for your investigation that showed this problem does not come from the fuel level sender unit... Link to comment Share on other sites More sharing options...
Aaron Posted August 30, 2017 Author Share Posted August 30, 2017 Thanks, Tom. It's been a bit of a dilemma getting here and all I find myself doing is questioning the competence of the Porsche technician that's programming the cluster. I'm going to get in touch with a specialist and get a second opinion. There's got to be some ammunition I can use against the dealer. Link to comment Share on other sites More sharing options...
tomprout Posted September 4, 2017 Share Posted September 4, 2017 FYI, I went to 2 different specialists one official Porsche dealer and one independent and none of them were able to fix the issue by calibrating the fuel gauge using piwis tool... I hope you will have more luck with you specialist... Link to comment Share on other sites More sharing options...
Aaron Posted September 5, 2017 Author Share Posted September 5, 2017 The specialist couldn't initiate a calibration, so I'm stuck with the dealer. Bugger. According to the service manual, they need to drain the tank, fill it with 13 litres and then calibrate it. Cardiff claimed to have calibrated it but between calling me to say they would calibrate it and calibrating it, there was 5 minutes or so at best. There's no chance they've drained the tank in that time. I called them Wednesday, got promised a call back and never received one. The same thing has happened today. Does anyone know if Porsche can be approached directly? I'm not sure what else I can do when the dealer is ignoring me. Link to comment Share on other sites More sharing options...
Aaron Posted September 5, 2017 Author Share Posted September 5, 2017 Having just done some research, I'm in Milton Keynes next week and there's a specialist with PIWIS 45 minutes away. I'll give them a call tomorrow. Link to comment Share on other sites More sharing options...
tomprout Posted September 5, 2017 Share Posted September 5, 2017 1 hour ago, Aaron said: The specialist couldn't initiate a calibration, so I'm stuck with the dealer. Bugger. According to the service manual, they need to drain the tank, fill it with 13 litres and then calibrate it. Cardiff claimed to have calibrated it but between calling me to say they would calibrate it and calibrating it, there was 5 minutes or so at best. There's no chance they've drained the tank in that time. I called them Wednesday, got promised a call back and never received one. The same thing has happened today. Does anyone know if Porsche can be approached directly? I'm not sure what else I can do when the dealer is ignoring me. Hi Aaron, I confirm this is the standard procedure that my dealer followed without any success. After that they called directly Porsche national HQ and the only reply from them was to suggest to change the instrument cluster. Before to visit the other specialist make sure to read again all the information I wrote. It can be useful for you to save some money Link to comment Share on other sites More sharing options...
Aaron Posted September 6, 2017 Author Share Posted September 6, 2017 The car has been booked back in with the dealer for Friday. They're confident they've set the wrong fuel tank size (I've spoken to the assistant manager). Link to comment Share on other sites More sharing options...
tomprout Posted September 7, 2017 Share Posted September 7, 2017 If you want to avoid another visit to your delaer I strongly suggest to ask them to validate my previous statement: <<- They tried to use Porsche piwis tool to set 54 liter option: The mark goes well to 8/8 when the tank is full but the low fuel reserve warning is triggered when the mark is just below 2/4 instead of 1/4. I strongly suggest to ask your dealer to remove some fuel and make sure you will not have the same issue in order to not having to bring them back again your car.>> Link to comment Share on other sites More sharing options...
Aaron Posted September 8, 2017 Author Share Posted September 8, 2017 I'm definitely keeping that in mind, Tom. I'm going to fill up at halfway or so (if they resolve it) to get an idea of how much fuel would be left in the tank. Link to comment Share on other sites More sharing options...
tomprout Posted September 8, 2017 Share Posted September 8, 2017 (edited) You have to fiil up a little bit more than halfway. If not then the gauge level will not be updated (Known issue on 996/987 models) Then drive so gauge level goes close to the reserve Edited September 8, 2017 by tomprout Link to comment Share on other sites More sharing options...
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