TM 5-3895-374-24-2 the  end  of  the  crankshaft.    thus  when  the  compressor  Is  In operation,  centrifugal   force   acts   upon   the   unloader   weights and   they   swing   outward.      (See   Figure   4-4).      When   the compressor    stops.        these    weights    retract,    (Figure    4-3) permitting the thrust pin spring to move the plunger and thrust pin  outward.    The  thrust  pin  opens  the  pilot  valve  and  the trapped air pressure escapes from the cylinder and intercooler through  a  passage  in  the  frame  end  cover  (See  Figure  4-5), through the unloader tube and to atmosphere through the inlet filter/silencer. Figure 44.  Position of weight and thrust pin when compressor Is operating.. When  the  compressor  starts,  centrifugal  force  acts upon   the   unloader   weights   and   they   swing   outward.      This permits the plunger and thrust pin to move inward and the pilot valve   to   close.      The   escape   path   to   atmosphere   for   the cylinder pressure is now closed and the compressor pumps air in a normal manner. If  the  pilot  valve  tube  line  is  excessively  hot,  it  is  a good indication that the pilot valve is leaking and adjustment is required. PILOT VALVE ADJUSTMENT To   adjust   the   pilot   valve,   refer   to   Figure   4-3,   and proceed as follows: 1 Stop the compressor.(Disconnect the electrical supply main switch to prevent accidental start-up. 2. Remove the pilot valve tube and the tube fittings. 3. Remove the pilot valve body and all existing shims. 4. Screw  the  pilot  valve  body  back  into  the  frame  end cover (without any shims) until contact with the thrust pin is felt Advance the pilot valve body 1/4 to 1/2 turn more. If   contact   with   the   thrust   pin   cannot   be   felt,   the following steps may be necessary to locate the contact point. a. Insert a small instrument (Punch.  rod, nail, etc.) into the  end  of  the  pilot  valve  until  it  contacts  the  valve stem. b. While still inserted in the pilot valve, make a mark on the instrument even with the outside edge of the pilot valve body. c. Keeping   the   instrument   pressed   lightly   against   the valve stem, screw the pilot valve body into the frame end  cover.  When  the  mark  on  the  instrument  starts moving out away from  the  edge  of  the  pilot  valve  body  contact  has been mace with the thrust pin. d. Advance the pilot valve body1/4 to 1/2 turn more and proceed with step five. 5. Measure  the  gap  between  the  pilot  valve  body  and the frame end cover (See Figure 4-3). 6. Remove  the  pilot  valve  body  and  add  enough  shims to fill the gap measured in step five. 7. Screw  the  pilot  valve  body  back  into  the  frame  end cover until the body is tight on the shims. 8. Reconnect the pilot valve tube and tube fittings. BREATHER/UNLOADER BY-PASS OPERATION  OF  THE  BREATHER/UNLOADER  BY- PASS The breather/unloader by-pass tube lines eliminates air pressure   build-up   in   the   compressor   frame   by   providing   a passage  for  the  air  to  escape  through  the  inlet  unloader  (if opened) or (if closed) through the check valve (See Figure 4- 5),  therefore.    by-passing  the  inlet  unloader  and  escaping  to atmosphere through the inlet filter/silencer. Figure 4-5.  Breather/Unloader By-Pass INTERSTAGE PRESSURE CHART (PSIG) MODEL COMPRESSOR DISCHARGE PRESSURE (PSIG) NUMBER 100 PSIG 150 PSIG 200 PSIG 250 PSIG 7.0 kg/cm² 10.5 kg/cm²    14.1 kg/cm} 17.6g/cm² 7100 37-40 40-43 44-47 47-50 3000 37-40 3942 40-43 ----- page 3 - 838