Fuel pump???

Dear All - I have a mildly irritating problem with fuel syphoning out of the line and back into the tank.

It's only really noticable if I leave her standing for more than a week, which unfortunately is more often than not these days.  The problem arises when I try to fire her up and can end up cranking her over until it flattens the battery.

It suggests to me that either there is a leak in the fuel line somewhere, although I can't find one, or the fuel pump is weak, however when she is running it's very smooth.  BTW it's the original mechanical pump not the electric type.

I guess I could fit a non-return valve but this might just be papering over the cracks.

Any ideas?  Thanks.

Thanks Richard.

I've got a copy of the 'bible', perhaps I should try reading it properly!!!