The leak detection pump puts two pounds of pressure on the fuel tank and supply system, then a sensor watches how long it takes for that pressure to bleed down. The hoses for the leak detection system cause more problems than the fuel supply system itself.
A slow leak would be caused by something like a loose hose clamp or a pinhole leak in a hose. That will set a different fault code for a "small leak". A smoke machine is useful for finding those. It injects white smoke into the system at about two pounds of pressure, then you watch for where the smoke comes out.
A large leak, other than the gas cap, usually involves a broken plastic pipe on the pump or a disconnected hose. Once you find the cause, it will usually be pretty obvious. I'm not sure where that pump is on your vehicle but it's generally underneath close to the gas tank. Start by looking for anything that may have been hit by road debris, and rusted or missing hose clamps.
Monday, February 7th, 2011 AT 10:05 PM