renault trafic t1100 hard to start ?

HI i have jest acquired a 1990 renault trafic camper with a 1721cc petrol engine and find it hard to get started, i have noticed after the van has stood for a few days that there is no petrol in the filter/pipe from the fuel pump to the carb, what i think is happening is when i crank the engine the fuel pump eventually pumps petrol to the carb and it starts after it starts everything is ok and it runs smoothly.i cant smell any petrol or see any leaks so the petrol must be draining back in to the tank any help into why the petrol is draining from the pipe would be appreciated