For the purpose of paying the pensions hereunder, a fund shall be created as follows:
If at any time there is not sufficient money in the pension fund for the purposes thereof, the governing body shall include in any tax levy a sum in addition to amounts theretofore contributed which shall be sufficient to meet the requirements of the fund. This sum shall be raised by tax levy no longer than is necessary to meet the requirements of the fund. Whenever the fund exceeds an amount which the governing body by resolution from time to time determines to be adequate for the fund, no moneys, except the four per cent of salaries and the fines, donations and rewards specified in this section, shall be paid into the fund unless and until the fund falls below the amount so determined to be adequate.
N.J.S. § 43:13-27