A320 Eng Start with external Pneumatics
 

When using external pneumatics to start first engine, does it make a difference if XBLEED is open or closed.

I can't see how it would but I'm told there might be a low pressure issue if it is left OPEN and that closing the XBLEED valve would reduce that chance. I'm inclined to think that if there is a lo press sit'n, then the problem is with the source of the air, and the XBLEED configuration has no bearing.

If the cart is not brilliant, it's best to close eveything else off so as to get as much air as possible to the engine you want to start.