[jrd22]

Our Yanmar does not have a drain plug in the pan so we have always had to use the dipstick tube. With the oil hot it has never been a problem getting the oil to vacuum up the tube. I agree with Ajari, try pulling the tube back a bit, maybe it is curling back up inside the pan up above the oil level. Straighten the tube as much as you can and then carefully push it down the tube until you just feel it hit something and stop there. It's either that or your new pump isn't working properly as suggested above.