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Many resonances in the reaction {sup 27}Al+{ital p} for {ital E}{sub {ital p}}=3.58--4.06 MeV were observed corresponding to excitation energies {ital E}{sub {ital x}}=15.03--15.50 MeV of the compound system {sup 28}Si. We measured the excitation functions for the decay mode with exit channels ({ital p}{sub 0--}{ital p4},{alpha}{sub 0},{alpha}{sub 1},{gamma}) in the above proton energy range with energy steps of 2 keV at 135{degree} and 145{degree} for proton and {alpha} particles and at 60{degree} for gamma rays. Two solid-state detectors and a 5.1 cm{times}5.1 cm NaI(Tl) scintillator were employed. High experimental resolution of {similar to}1 keV enables us to deduce the average {sup 28}Si level spacing in the region of 15 MeV excitation. The structure of resonances is discussed and energies, together with widths of resonances, are presented. The {ital J}{sup {pi}} assignment for several resonances was proposed as well.