Questioning the reliability of the 996 (starting problems) + Fuel Vent System(PICS)
06-24-2010, 03:01 PM
#62
Three Wheelin'
I should have elaborated on the sender thing. I don't mean to give elementary advice to a seasoned mechanic, so pardon me if you find this post too simplistic, just take it for what it is or isn't worth:
I noticed you replaced the fuel pump. When you reinstalled the sending unit, did you notice a marking on it? You would have to turn that marking to match a similar marking on the tank itself. I also thought that it was possible that in fact your original error was a faulty or miscalibrated sending unit which was informing the computer that the car was empty when in fact it was not. Since calibration is fairly simple if you have someone nearby who will hook up a pst, i thought it was worth giving you the procedure.
Even fairly seasoned DIYers rarely get too deep into the fuel tanks on these cars, but I'll share some thoughts:
0. Invest in the durametric software, as a DIY guy you will find it invaluable in working on these cars
1. You replaced the fuel pump, but did you measure flow with the new pump and the tank down to 1/4? If it's not giving you enough pressure, it could be the tubes or venturis in the tank itself. It could be the fuel lines (including the return line if Mk1, bosch systems rely on return as well). It could be the filter.
Nominal test values:
Stationary engine 3.8 ± 0.2 bar
Engine idling 3.3 ± 0.2 bar
2. If your fuel gauge/trip computer is reporting incorrectly empty or lower than actual, might be worth replacing and recalibrating the sending unit just to eliminate. Cheap. http://cgi.ebay.com/ebaymotors/ws/eB...1#ht_500wt_751
3. Just to eliminate possibilities in ignition, you should bridge the clutch interlock switch (and inspect that fuse) and the ignition switch should also be inspected and replaced if necessary.
I really, highly recommend visiting the 996 section at renntech.org, downloading some manuals at http://www.cannell.co.uk/Manuals.htm, and searching renntech's forums. It is a much more technical forum, and you're more likely to see a similar issue there.
Finally with regard to your intuition about a connection to the vent system, take a look at it, I've seen stranger things. The fuel filler neck and gas cap also should be inspected. Look at all the fuses and switches that prevent ignition. I have an MB that wouldn't start at a gas station last month. It was a faulty brake light switch, $8, just coincidental. You never know.
I noticed you replaced the fuel pump. When you reinstalled the sending unit, did you notice a marking on it? You would have to turn that marking to match a similar marking on the tank itself. I also thought that it was possible that in fact your original error was a faulty or miscalibrated sending unit which was informing the computer that the car was empty when in fact it was not. Since calibration is fairly simple if you have someone nearby who will hook up a pst, i thought it was worth giving you the procedure.
Even fairly seasoned DIYers rarely get too deep into the fuel tanks on these cars, but I'll share some thoughts:
0. Invest in the durametric software, as a DIY guy you will find it invaluable in working on these cars
1. You replaced the fuel pump, but did you measure flow with the new pump and the tank down to 1/4? If it's not giving you enough pressure, it could be the tubes or venturis in the tank itself. It could be the fuel lines (including the return line if Mk1, bosch systems rely on return as well). It could be the filter.
Nominal test values:
Stationary engine 3.8 ± 0.2 bar
Engine idling 3.3 ± 0.2 bar
2. If your fuel gauge/trip computer is reporting incorrectly empty or lower than actual, might be worth replacing and recalibrating the sending unit just to eliminate. Cheap. http://cgi.ebay.com/ebaymotors/ws/eB...1#ht_500wt_751
3. Just to eliminate possibilities in ignition, you should bridge the clutch interlock switch (and inspect that fuse) and the ignition switch should also be inspected and replaced if necessary.
I really, highly recommend visiting the 996 section at renntech.org, downloading some manuals at http://www.cannell.co.uk/Manuals.htm, and searching renntech's forums. It is a much more technical forum, and you're more likely to see a similar issue there.
Finally with regard to your intuition about a connection to the vent system, take a look at it, I've seen stranger things. The fuel filler neck and gas cap also should be inspected. Look at all the fuses and switches that prevent ignition. I have an MB that wouldn't start at a gas station last month. It was a faulty brake light switch, $8, just coincidental. You never know.
06-24-2010, 03:03 PM
#63
Well said.
...On to your problem. I think you're on the right track. An important clue is that your problems occurred at the gas station while filling the tank. Therefore, it might make sense to familiarize yourself with the vapor recovery system. May I suggest purchasing a full set of service manuals (you may be able to find a set for free download on the internet). These are really necessary if you what to maintain the car yourself and will provide you information on how to troubleshoot and test various systems in the car.
On the bright side, these "little" issues provide a chance to get in there in learn about your Porsche.
Good luck!
Joe
...On to your problem. I think you're on the right track. An important clue is that your problems occurred at the gas station while filling the tank. Therefore, it might make sense to familiarize yourself with the vapor recovery system. May I suggest purchasing a full set of service manuals (you may be able to find a set for free download on the internet). These are really necessary if you what to maintain the car yourself and will provide you information on how to troubleshoot and test various systems in the car.
On the bright side, these "little" issues provide a chance to get in there in learn about your Porsche.
Good luck!
Joe
06-24-2010, 07:54 PM
#64
I should have elaborated on the sender thing. I don't mean to give elementary advice to a seasoned mechanic, so pardon me if you find this post too simplistic, just take it for what it is or isn't worth:
I noticed you replaced the fuel pump. When you reinstalled the sending unit, did you notice a marking on it? You would have to turn that marking to match a similar marking on the tank itself. I also thought that it was possible that in fact your original error was a faulty or miscalibrated sending unit which was informing the computer that the car was empty when in fact it was not. Since calibration is fairly simple if you have someone nearby who will hook up a pst, i thought it was worth giving you the procedure.
Even fairly seasoned DIYers rarely get too deep into the fuel tanks on these cars, but I'll share some thoughts:
0. Invest in the durametric software, as a DIY guy you will find it invaluable in working on these cars
1. You replaced the fuel pump, but did you measure flow with the new pump and the tank down to 1/4? If it's not giving you enough pressure, it could be the tubes or venturis in the tank itself. It could be the fuel lines (including the return line if Mk1, bosch systems rely on return as well). It could be the filter.
Nominal test values:
Stationary engine 3.8 ± 0.2 bar
Engine idling 3.3 ± 0.2 bar
2. If your fuel gauge/trip computer is reporting incorrectly empty or lower than actual, might be worth replacing and recalibrating the sending unit just to eliminate. Cheap. http://cgi.ebay.com/ebaymotors/ws/eB...1#ht_500wt_751
3. Just to eliminate possibilities in ignition, you should bridge the clutch interlock switch (and inspect that fuse) and the ignition switch should also be inspected and replaced if necessary.
I really, highly recommend visiting the 996 section at renntech.org, downloading some manuals at http://www.cannell.co.uk/Manuals.htm, and searching renntech's forums. It is a much more technical forum, and you're more likely to see a similar issue there.
Finally with regard to your intuition about a connection to the vent system, take a look at it, I've seen stranger things. The fuel filler neck and gas cap also should be inspected. Look at all the fuses and switches that prevent ignition. I have an MB that wouldn't start at a gas station last month. It was a faulty brake light switch, $8, just coincidental. You never know.
I noticed you replaced the fuel pump. When you reinstalled the sending unit, did you notice a marking on it? You would have to turn that marking to match a similar marking on the tank itself. I also thought that it was possible that in fact your original error was a faulty or miscalibrated sending unit which was informing the computer that the car was empty when in fact it was not. Since calibration is fairly simple if you have someone nearby who will hook up a pst, i thought it was worth giving you the procedure.
Even fairly seasoned DIYers rarely get too deep into the fuel tanks on these cars, but I'll share some thoughts:
0. Invest in the durametric software, as a DIY guy you will find it invaluable in working on these cars
1. You replaced the fuel pump, but did you measure flow with the new pump and the tank down to 1/4? If it's not giving you enough pressure, it could be the tubes or venturis in the tank itself. It could be the fuel lines (including the return line if Mk1, bosch systems rely on return as well). It could be the filter.
Nominal test values:
Stationary engine 3.8 ± 0.2 bar
Engine idling 3.3 ± 0.2 bar
2. If your fuel gauge/trip computer is reporting incorrectly empty or lower than actual, might be worth replacing and recalibrating the sending unit just to eliminate. Cheap. http://cgi.ebay.com/ebaymotors/ws/eB...1#ht_500wt_751
3. Just to eliminate possibilities in ignition, you should bridge the clutch interlock switch (and inspect that fuse) and the ignition switch should also be inspected and replaced if necessary.
I really, highly recommend visiting the 996 section at renntech.org, downloading some manuals at http://www.cannell.co.uk/Manuals.htm, and searching renntech's forums. It is a much more technical forum, and you're more likely to see a similar issue there.
Finally with regard to your intuition about a connection to the vent system, take a look at it, I've seen stranger things. The fuel filler neck and gas cap also should be inspected. Look at all the fuses and switches that prevent ignition. I have an MB that wouldn't start at a gas station last month. It was a faulty brake light switch, $8, just coincidental. You never know.
2. I did notice the marker on the fuel level sender, I lined it up during install. The fuel filter has been replaced, the relay as well.
3. Also, I have jumped the clutch interlock switch already.
That online manual is only partial, not even close to being complete.
BTW: It is not a good time opening the fuel tank. Do you have a diagram of the fuel vent system?
06-24-2010, 07:58 PM
#65
06-24-2010, 08:57 PM
#66
Nordschleife Master
Just throwing a shot in the dark (imagine that
) but could this be a fuel pump issue? If there is any debris clogged it could mimic the same symptom. I had that issue in my RS America. Change the fuel pump and voila!
06-24-2010, 09:15 PM
#67
When i replaced the fuel pump a month or so ago there was not much sediment in the bottom of the tank and the small filter element on the old pump was barely covered. I doubt the new pump is clogged. Have any experience with the vent system for the fuel tank?
I just thought of something else that may help solve the issue. My last time at the fuel pump when it broke down. I filled it up until the pump nozzle clicked and stopped flow, (like usual) i tried to top it off and the fuel squirted out at me a little bit. That usually never happens. Any ideas?
06-24-2010, 09:28 PM
#68
Nordschleife Master
Good call on the pump since you check the filter element and any debris in the tank. If it isn't burned out you can reverse the pump to clear out any debris but since it is new and the tank is clean we can almost certainly rule that out. It does sound more and more like a venting issue, doesn't it? I have absolutely zero experience with that. However, the collective here has got to have somebody that has been in the vent system.
Guys???
Guys???
06-24-2010, 09:37 PM
#69
Much missed
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Hope this helps.
link to RennTech
1 - EVAP canister purge valve
2 - EVAP canister
3 - Purge air
4 - Tank
5 - Pressure sensor
6 - Shutoff valve
7 - Operating purge valve
8 - To intake manifold
9 -Vacuum control valve
link to RennTech
1 - EVAP canister purge valve
2 - EVAP canister
3 - Purge air
4 - Tank
5 - Pressure sensor
6 - Shutoff valve
7 - Operating purge valve
8 - To intake manifold
9 -Vacuum control valve
06-25-2010, 12:14 AM
#72
How do you go to revert the fuel pump ? I mean I wonder how that work..where does the gas go ?
I am struggling with a fuel thing myself and I suspect the computer would shut down the fuel pump in case there is too much 'negative pressure'/suction, in order to prevent any damage to the fuel pump. So the question is what is releasing the pressure in the tank, is that the "1 - EVAP canister purge valve" ? If yes I wonder where is is located ?
I am struggling with a fuel thing myself and I suspect the computer would shut down the fuel pump in case there is too much 'negative pressure'/suction, in order to prevent any damage to the fuel pump. So the question is what is releasing the pressure in the tank, is that the "1 - EVAP canister purge valve" ? If yes I wonder where is is located ?
06-25-2010, 08:45 AM
#74
How do you go to revert the fuel pump ? I mean I wonder how that work..where does the gas go ?
I am struggling with a fuel thing myself and I suspect the computer would shut down the fuel pump in case there is too much 'negative pressure'/suction, in order to prevent any damage to the fuel pump. So the question is what is releasing the pressure in the tank, is that the "1 - EVAP canister purge valve" ? If yes I wonder where is is located ?
I am struggling with a fuel thing myself and I suspect the computer would shut down the fuel pump in case there is too much 'negative pressure'/suction, in order to prevent any damage to the fuel pump. So the question is what is releasing the pressure in the tank, is that the "1 - EVAP canister purge valve" ? If yes I wonder where is is located ?
