The full faith and credit of the city are hereby pledged for the prompt and full payment of the principal and interest on all improvement bonds made payable from the consolidated improvement bond debt service fund, and the city council shall provide money for the payment of such principal and interest when due and, if needed for such purpose, levy a direct ad valorem tax on all of the taxable property in the city without limitation as to rate or amount. (1981 Code 110 § 5)