Full Version: Gas tank ventilation
My 914 loses fuel pressure after running for a while. I have put a pressure guage at the carburators and see the pressure dropping from 3 psi to zero. Does the fuel tank need to be ventilated on a 76 914 when running carbs? I have changed the fuel lines including the line through the tunnel. If ventilation is needed any suggestions on how to best do it. I have pulled the pick up screen and the fuel pump is a 3 1/2 psi pump from cb performance
QUOTE(ice cold @ Jun 28 2014, 08:18 AM) 
My 914 loses fuel pressure after running for a while. I have put a pressure guage at the carburators and see the pressure dropping from 3 psi to zero. Does the fuel tank need to be ventilated on a 76 914 when running carbs? With the fuel cap off the car doesn't appear to lose pressure. I have changed the fuel lines including the line through the tunnel. If ventilation is needed any suggestions on how to best do it.
Fuel tanks always need to be vented. Always! You should have a vent near the cap that goes into the expansion tank. The expansion tank connects to the charcoal canister.
...........and the charcoal canister is connected to both the fan shroud and the air cleaner, providing air flow to remove vapor and burn it.
The Cap'n
The Cap'n
I purchased the car several months ago. There are the two fitting on the bottom of the tank for supply and return. Just checked and you are correct the expansion tank is ventilated. Next step will to be pulling and checking the fuel pump outside of the car.
Does it keep running if you leave the gas tank cap off?
On my Ghia, I had a case where debris in the tank was causing exactly the same symptoms you are describing.
However these tanks have a sock around the fuel pickup, so that is far less likely (assuming you still HAVE a sock in the tank.)
On my Ghia, I had a case where debris in the tank was causing exactly the same symptoms you are describing.
However these tanks have a sock around the fuel pickup, so that is far less likely (assuming you still HAVE a sock in the tank.)
QUOTE(ice cold @ Jun 28 2014, 08:51 AM)
I purchased the car several months ago. There are the two fitting on the bottom of the tank for supply and return. Just checked and you are correct the expansion tank is ventilated. Next step will to be pulling and checking the fuel pump outside of the car.
Since this has been converted to a carb setup, did someone plug the air hoses that go from the charcoal canister all the way back to the air-cleaner?
If so, they plugged the tank ventilation shut!
Sounds like the small vent line is plugged (ask me how I know). I had driven my carbed car for many years with no problem, but one day after driving around most of the day,the car started sputtering. Pulled off road and started checking all sorts of things, and eventually thought to open gas cap in case my level gauge was just reading wrong. When I unscrewed the cap, lots of whooshing sounds and popping of tank metal as the vacuum was released in the tank.
I had plugged the return and vent lines back at the firewall when restoring the car. After doing some research, realized the gas tank cap does not relieve for vacuum, and I then installed a small one-way valve on vent line at the firewall. No problems since, even after driving car for 4 hours on highway.
I had plugged the return and vent lines back at the firewall when restoring the car. After doing some research, realized the gas tank cap does not relieve for vacuum, and I then installed a small one-way valve on vent line at the firewall. No problems since, even after driving car for 4 hours on highway.
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