Has anybody any experience of fuel problems on an old Yanmar mini mustang mini digger.

There is fuel going into the pump when I manually pump it but none coming out. I've removed the pump and checked the barrels at the top but to no avail.

 On the top of the pump there are three outlets for the cylinders. There are nuts holding the pipes to the outlets and the outlets themselves have threaded retainers to hold the pump barrels together. If I remove the pipes, I still get no fuel. If I loosen the retainers, I get fuel at all three every time I pump manually. I assume therefore that these should be locked tight.

 Any ideas anybody.