This manifests itself as a strong smell of fuel when starting the car or whilst running. First thing to try is to look at the fuel injector seals in the inlet manifold whilst the fuel pump primes (ignition switch on - but not start). Have someone stare at the top of the four injector seals and check that the seals remain dry after the fuel pump primes. If one or more bleeds fuel it can be the seals themselves or the actual fuel injector body which leaks.
The cheap fix to try is to replace the seals first, if it still leaks, you will need to replace the fuel injector.
The picture shows the orifice where the fuel was leaking out from on the injector.
When re-installing the injectors use clean engine oil on the o-ring seals to stop them from tearing.