I think the solenoid is on the fuel rail. It might be on the plenum. Its job is to capture and release residual fuel vapour when the engine is switched off. This is then fed into that canister that is inside the driver's wheelarch.
The canister is full of carbon and this absorbs the fuel vapour, presumably to stop the car smelling of fuel and also reduce the risk of the fuel ending up somewhere it shouldn't like a hot manifold or somethng. Vapours are a lot more explosive than liquid petrol.
Locate the rubber pipe that leads to the inner wing and trace it back to the solenoid.
Also search this site for 'wiring diagrams' to check the number of wires and their colours.
Hope you have an easy fix.