|
|
Post by 90GTVert on Mar 29, 2012 15:05:01 GMT -5
The petcock is actually a valve. A vacuum actuated valve. Vacuum is applied to a spring loaded rubber diaphragm inside that opens the valve to allow fuel to flow to the carb. The spring closes the valve when vacuum is absent. They sometimes go bad. Either they get gummed up from sitting un-used for extended periods or they get sediment/tank rust/grit in them that makes them stick open or the diaphragm itself can fail. You'll see them listed as a "fuel pump" on many parts sites. That is incorrect. They do not pump the fuel. The fuel simply runs downhill due to gravity.
There are two types of these valves. One mounts to the tank bottom and has a strainer that protrudes up inside the tank to filter out sediment/debris. The other is frame mounted and is fed through fuel line. On the frame mounted ones it's best to install an in-line fuel filter between the tank and the valve because there is no strainer in the tank with a frame mounted setup.
Tank mounted unit:
Frame mounted: |
|
