RE: [alfa] Fuel Tank Vapor Pressure Buildup

["John S." <roadtrip999@xxxxxxxxxxx>]

I think the problem is a plugged up vent system. Since the atmospheric 
pressure is much more down low, if you seal the tank, then climb up a 
mountain to where the pressure is much less, there will be a very 
significant pressure buildup in the tank. Conversly, if you seal the tank, 
then burn down fuel, you'll get a vacuum and make the fuel pump work extra 
hard and may even cause fuel starvation.

The "fuel pressure problem" you are thinking of was due to the main fuel 
supply pump being unable to pull the fuel out of the top of the fuel tank 
starting in '77. Alfa retrofitted those cars with an in-tank boost pump to 
supply a positive head of pressure to the main supply pump. It had nothing 
to do with the vent system.

The culprit in your case is most likely that the metal tube inside the 
plastic vapor recovery tank is rusted-shut . . . . very common. Remove the 
tank (just held by a rubber strap, then remove the short rubber tube at the 
top fitting and withdraw the metal tube. Clean it out. Also make sure that 
the vinyl tubing from that fitting up to the metal tube on the intake 
manifold is clear and in good shape. Fuel resistant vinyl tubing like that 
is available very cheaply in hardware stores.

Here's a link to a schematic with a picture of the metal tube:

http://www.alfabb.com/bb/forums/showthread.php?t=6797&highlight=vapor+recovery+tank

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