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Does it not need to be near something like a gas nozzle (i.e. steel) to close the circuit and open the vent? When it is just sitting on the (wooden) table, the resistance is infinite. Only when I press it against a magnet does the resistance approach zero. I would have thought there was a magnet in it, i.e. when it senses the pump nozzle it closes the circuit and allows air to leave the tank (via the charcoal canister). I am beginning to understand why they redesigned this system on the 997. Only Porsche could so overengineer what is effectively a hole to pour a liquid through.
So, the small magnetic sensor was placed back into the groove in the plastic part of the vent valve which attaches to the fuel filler pipe. Next trip to the gas station - no joy. The fuel spat back out as usual. This morning I unplugged the magnetic sensor and checked it with an ohmmeter - full resistance. I then pushed a large diameter socket extension into the filler neck (to approximate a fuel filler nozzle). Full resistance. I then pulled the sensor from the car and bench tested it by placing it on a large chunk of steel. Full resistance. Finally, I placed a magnet on it - finally, the resistance dropped to near zero. Am I bench testing it properly? Is it supposed to detect the presence of a steel gas station filler nozzle when placed into the fuel tank filler pipe? So far I have replaced the vent valve and the gas cap without luck. I have also checked the fittings at the top of the tank. Besides the vent for the charcoal canister, I am running out of options. Thank for the help so far, I would not have diagnosed the issue to this extent without help from this site.
Will have a chance to look at it on Thursday after work. Fingers crossed.
Ah! That little cylindrical thingy connects to the gas tank vacuum switch where it pokes out of the vent valve. Mine is not connected, and was not connected when I examined it before I replaced it. That might be it. Thanks! Something to try this weekend.
Where would it be? (It does not look familiar). I open the fuel cap, look in, I see a metal disk with a hole covered with a flap on a spring. Not much else. When I fill it with a funnel and a gas can, it fills fine (albeit slowly). Thanks.
johnmh posted a topic in 996 Series (Carrera, Carrera 4, Carrera 4S, Targa)I know this has been covered, but all the posts seem to start with a direction to 'read the posts', which is less than helpful. I have the apparently common problem whereby I need to use a teaspoon when I fill my '01 996, or it will petulantly spit its breakfast all over my shoes. The car has done this since I brought it back to life last fall. I have replaced the fuel line vent valve, checked the mythical E6 fuse (not sure what it does or what it powers, but mine seems the picture of health). I cleaned a ground spade connector which connects to the alloy bracket which secures the fuel line vent valve to the fuller neck. I have also pulled the battery and tank cover plate (when I installed a new fuel pump earlier this week), all the hoses seem good (no mice) and properly connected with a 'click'. From what I can tell, the fuel tank vents through a small diameter hose which connects to the vent valve via a canister. It appears that the air displaced by incoming fuel has nowhere to go; something in this Rube Goldberg Porsche design has gone awry, or never worked from inception. Apparently there is a factory bulletin on this issue? Is there a number / date for it, or is there an online source for these? The fuel line vent valve is a purely mechanical thing? It seems to have no place to plug any wire in to it, so I am not sure how it decides to open or close. Thanks to all for any insight which you can share.
Tank is clean inside, except for a few tiny, broken zip ties. Screen on the bottom of the tank is discolored, but not plugged. This may be a good reason to keep the tank topped up. Comparatively speaking, this has been easy to do (unless I damage the fuel level sender when I reinstall it). I suspect as the entire car was a study in deferred maintenance, the fuel filter may also have had something to do with its demise. Yes, my car was sold new in Georgia, lived in Texas for a while, was exported to Canada, and then brought to Dubai by a Canadian who moved here. It's not done traveling yet, I eventually want to ship it to my place in Italy where it will be holiday daily driver. If I do that I should take it for a road trip to Stuttgart to close the circle.
Scary stuff, but I am not certain there would be enough oxygen in the tank to actually catch fire.
Fuel pump is toast. No errors displayed on Durametric. No fuel pressure. Fuse ok, jumped pump relay made no difference. I drained the tank and pulled the pump. Wow. All insulation burned off one wire. Wire itself dangling free, not connected to pump as the pump electrode melted through and detached. All plastic near the electrode melted to a black crisp on the top of the pump body. Amazing this much current could do this damage without burning through a 30A fuse or a relay. No detritus in the tank, but the rubber seal around the top had turned to black goo. How did this thing not torch itself? I was very lucky. Will post pictures later.
I added fuel to the tank and checked the 30A fuse (neither were the issue). I will use the Duramteric tomorrow and measure fuel pressure, but just so I understand where all the relevant electrical components are - there is one fuel pump relay on the board under the dash above the fuse box, and a second one in the back of the car (underneath the convertible top tray)?
Got the car back and turned the engine over. Tach needle moves up ever so slightly. Perhaps the CPS is ok. My order from Pelican will only arrive early next week, so plenty of time for diagnostics this weekend.
Thanks for the suggestions, I get the car back tomorrow (it was in having the convertible top fixed) so I can check that then. Is the 60 sec / off for 10 sec necessary to generate error codes? Yes, I have a durametric scanner. Do the fuel pressure regulators fail on these cars?
Interesting, so the CPS signal dictates spark timing as well as sending a signal to the relay which feeds power to the fuel pump? Is there not a cam position sensor which plays a role in spark timing as well? FWIW, I was wrong about the Testarossa, the tachometric relay only permits the fuel pumps to get power, the spark timing is established by a combination of two distributors and a Marelli ECU which sets advance. Out of an abundance of caution I added a CPS to my Pelican order of a pump, a relay and a 30A fuse. If you replace everything, it must work, no? Unless it is out of gas....
The car will turn over, catch on a cylinder or two, but not actually run. To my mind, that may rule out spark, but not fuel. So the crank position sensor actually needs to deliver a signal before the fuel pump will switch on (a typical safety feature)? My Testarossa uses a tachometric relay which shuts the fuel pumps off when the car is not running, in order to prevent the fuel pumps from running after an accident which stops the engine from running. The thing is, with a bad tachometric relay, the TR will not even catch on a single cylinder, as there is no signal to tell it when to spark. Would a failed crank position sensor on a 996 also result in no spark, as the CPS needs to tell the engine when to spark?
Awesome. Thanks. Will check the fuse and relay first. And the fuel level in the tank...