no, your engineer can only sign off on the work done to date (at any particular stage) and must included how much is left to complete.
essentially, when you are self-building, you need enough cash to pay for all the work up to the first stage payment, then drawdown first installment from bank, then you need cash to pay for work from 1st to 2nd stage, then drawdown next installment, etc.
if you don't have any cash to start you'll have to talk to your bank or get a loan as the previous poster mentioned.