TM 9-2320-279-10-1 Change 8 2-41 Table 2-1. Preventive Maintenance Checks and Services for Models M977 thru M985E1 Location Item No. Interval Item to Check/ Service Crewmember Procedure Not Fully Mission Capable If: DRIVER 12 Before Fire Extin- guisher Continued b.  Check gage for proper pressure of about 150 psi (1 034   kPa).   Make   sure mounting is secure. b.  Pressure gage needle in RE- CHARGE area. c.  Check for damaged or missing seal. c.  Seal   broken   or missing. 13 Before Instru- ments a.  Start engine. a.  Engine   will   not start. b.  Tachometer. 1. Non-FHTV model vehicles.  Check tachometer for damage, operation, and condition. Correct idle is 625 to 725 rpm. b. 1. Tachometer indicates   less   than 600 rpm or more than 800 rpm. 2. FHTV model vehicles. Check tachometer for damage,    operation    and condition. Correct idle is 700 rpm when engine is hot. 2. Tachometer indicates   less   than 700 rpm or more than 725 rpm when engine is hot.