30 CFR § 36.21
Engine for equipment considered for certification
Only equipment powered by a compression-ignition (diesel) engine
and burning diesel fuel will be considered for approval and
certification. The starting mechanism shall be actuated
pneumatically, hydraulically, or by other methods acceptable to MSHA.
Electric starting shall not be accepted. Engines burning other fuels or
utilizing volatile fuel starting aids will not be investigated.
[Sched. 31, 26 FR 645, Jan. 24, 1961, as amended at 61 FR 55526, Oct. 25, 1996]