2001 E350 Class C fuel leak

[Bo]

We have a small, 21 foot, Ford Super Duty E350 based motorhome. If the fuel tank is filled completely it leaks out of the top and runs under the motorhome. This happens most often when the motorhome front is slightly lower than the rear when filling the tank. Even when I stop at the first fuel cutoff I still get a pool of fuel on the ground. Associated with this, I think, is an engine diagnostic code indicating a gross evaporative control system leak which usually is due to a loose fuel cap. We continually get this fault code and sometimes get a SES along with it. Before I drop the tank I'm trying to determine if this is a common problem with this chassis and if so what is the cause. Any help or advice will be appreciated.

[Bo]

We have a small, 21 foot, Ford Super Duty E350 based motorhome. If the fuel tank is filled completely it leaks out of the top and runs under the motorhome. This happens most often when the motorhome front is slightly lower than the rear when filling the tank. Even when I stop at the first fuel cutoff I still get a pool of fuel on the ground. Associated with this, I think, is an engine diagnostic code indicating a gross evaporative control system leak which usually is due to a loose fuel cap. We continually get this fault code and sometimes get a SES along with it. Before I drop the tank I'm trying to determine if this is a common problem with this chassis and if so what is the cause. Any help or advice will be appreciated.