jlturpin

I picked up a 93 968 Coupe with 66K miles on it. On my 600 mile drive home there was excessive pressure built in the fuel tank. It seems to build the pressure even on shorter trips (50 miles). When the fuel cap is removed, there is a 3-5 second spew of gas fumes. Any help would be appriciated.

KuHL 951

I thought all tanks today are supposed to build a positive pressure. They even test the caps during smog inspections for this very reason. I have 2 P-cars and a luxobarge, all of them let out that strong hiss on a warm day.

jlturpin

Not just a strong hiss, I have owned several P-cars and worked on many and have never seen this kind of pressure in a fuel tank. The tank does not seem to be venting at all.

cjeckert

When i open my tank it usualy takes 30-40 seconds for the pressure to release on a hot day.

Mighty Shilling

ditto... I actually had a thread on this, and someone said the vent lines were clogged. to get to them, you need to remove the fuel tank... to remove the fuel tank, you need to remove the transmission... I decided since there was no change in performance, I'll go ahead and leave it...

MoeJoe

My Haynes manual sudgests that you can remove the fuel tank with the tranny in place. I asume that maybe the rear bumper has to be removed. Don't our cars have a vapor recovery system that vents the gas tank?

Mighty Shilling

no, I checked on many occasion. on the 924S, you must remove the transmission to get to the fuel tank. removing the rear bumper will do nothing for clearance. maybe if you took a hacksaw to the spare tire well....

KuHL 951

There's no way to drop the tank w/o dropping the trans, especially the 85.5+ saddle tank. The early steel tank can be tipped a bit but not enough to get to anything above. You can get to the fuel sending unit from inside though. The fuel systems on any modern cars are not supposed to vent to atmosphere. Isn't it a closed loop with fumes going back into the intake tract after the charcoal canister? That's always been my impression.

jlturpin

On the 968 there is a tank ventilation valve (electronic) between the canister and the intake manifold. When I unplugged the terminal connection, it started venting. It also has a vacuum actuated valve as well.