[durtkillon]

My car gets really stinky on hot days both inside and outside the cabin at the rear of the gas tank. If the temp is over 90 degrees, I hear a gurgling sound from a tube at the back of the gas tank that emits just noxious gas fumes. It looks like an overfill tube of some type, but I figure it must be have a pressure release valve somewhere. I really don't understand how the car is supposed to manage pressures built up from an increase in temperature, but it appears that the fumes seep both inside and outside the car when the pressure builds.



I had my tank pressure tested and it's OK. An inspection of the lines , filler neck, etc. were OK. There are no drips anywhere.



Does anybody else experience this? I live in New Mexico, so 90-100 temps in the summer are pretty typical.



Does anybody have a diagram of the fuel system? The parts diagrams leave a lot to interpret.

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[Rap]

Thank god. I just had a plate, not sure if that is correct terminology replaced in the trunk because of the gas odor. They had another fix which involved a valve but of course concluded this fix worked. I thought perhaps it was worse after a fill up. It never occurred to me that heat might play a factor. I am going to have to call Provost back to see what the other fix was.

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[Chris Vais]

I believe that part of the air emissions control system includes a fuel tank vent line that is supposed to capture any overfill and vapors from the fuel system. If the line itself has failed or if it is plugged you might get the problem with fuel vapors you describe.

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[jaap]

I just went through a lot of effort finding out why the fuel tank was not venting an building up pressure wehn hot. From this I learned that this venting system is quite complex. The tank itself has two vent lines that connect to the filler neck. from there a line goes to a small expansion tank in the C-pillar(on a coupe). From there a line goes through a safety valve (not pressure valve but just to prevent fuel spilling when you are upside down) to the front of the car where there is a charcoal cannister in the left wing. Then a vent line goes from the cannister all the way back and exits just behind the fuel tank. The cannister is also connected to the intake manifold so that it can 'clean' the cannister from collected fuel vapor (when engine is running and certain temp. conditions are fulffiled).

In my car the vent line to the front of the car was stuck between the tank and body so not venting anymore. In your case since fuel smell is present behind the tank it could be that the cannister is no longer able to hold the fuel vapors.Sometimes the material disintegrates.



Jaap

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[johns_968]

I am also experiencing similar problems. When it's hot and the tank is close to full I get fuel vapor smells in the cabin and trunk of the car.



Less so when tank is close to empty but I hate running on low tank.



My local mechanic is planning on doing a smoke test of the fuel evap system to determine if there are any leaks on that side of the fuel system. He doesn't suspect a problem on the supply side.



If he gets his hands on that smoke machine and does the test with any positive results I'll post them here.

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[nissanite]

I have the same type of problem. When we get the odor on the track car, the fuel tank is under extreme pressure. If you remover the fuel cap it will vent fumes for 20 to 30 seconds.



When running mostly full throttle on the track the intake system will not pull out the vapors.

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[jaap]

Even if the intake system does not pull out the vapors there still should not be a presure build up in the tank. The only purpose of the cannister is to absorb the fuel in the vapors running through it. The ventline should be free to let air in and out. In my car the vent line got stuck and pinched between the tank and car body. Other failures are that the cannister itself gets blocked due to charcoal breaking up closingof the vent line to the rear of the car.



Jaap

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[durtkillon]

I'm getting my car back today from my mechanic. He said they tested the safety and check valves. They were OK. The charcoal can was breathing fine. I can't say whether it's absorbing correctly. There are still no visible leaks anywhere. He pressurized the system again and got the smell to come out the back of the tank, but it was not detectable inside the car like I've witnessed.



Jaap, do you know the system well enough that you could sketch a diagram out with all the valves, canister, expansion tank, etc? I know this system is complex, but I'm sure there is a smart way to troubleshoot it if I just understood how it's layed out. It sounds like you've already done the work to understand the system.



The gurgling noise from behind the tank should not be happening if I understan how you described that line. Gurgling implies there is a restriction or the vent line is acting like a p trap. Maybe there is fluid in some part of the vent line.



Also, can you describe where the pinched line is located? I'd like to check that.

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[Lonestar968]

Kurt,

I also suffer from the same EXACT problem. It is especially noticeable on hotter days (90+). I have also experienced the same gurgling sound you mention. It seems loudest immediately after shutting off the engine following a drive, and dissipates after it sits (engine off) for 1-2 minutes. Since you're in Corrales, I'm guessing you're a RRR member and if you are, try to contact Bob Blackwell, he has experienced alot of 968-related anomolies over the years.



I'm going to start a different thread about another little unexplainable, yet related, tid-bit which happened the other day as the car was going, nose-up, onto a flatbed wrecker (long story). Fuel was seeping sufficiently that it made a nice little stream of fuel on the wrecker bed and dripped off of the end. The fuel seemed to be coming from the fuel filler neck area, though I couldn't pinpoint exactly where it was leaking from. Pretty freaking alarming, to say the least!



I am very interested in finding out more about the mysterious gurgling noise, charcoal canister, vent lines, etc from your original post and the ones that followed.



Dan

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[MCL968]

I just spoke to the mechanic and there seems to be a lot of staining on the rear of the gas tank from fuel coming out of the vent line just above the rear of the tank.



It seems the vent line is supposed to be open, but somewhere there (I believe) is a valve that is supposed to prevent fuel from coming out of this hose.



Anyone out there know where this valve is, or perhaps what could be causing raw fuel to come out of this vent line?

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[Ryan]

Look on a copy of PET and I think it has an exploded view with all parts

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[banditsc]

The valve that controls the evap system for the fuel tank is in the engine bay, close to the master cylinder.

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[MCL968]

How could this result in raw fuel going up the line and out the back by the tank?

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[banditsc]

One of the failure modes is for it to have continuous suction on the tank, on the 928 it causes the tank to implode. It's vacuum operated, I suppose you could try plugging the vac line and see if the symptoms change.

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