Pic. 6-2. Vacuum booster:
1 - stock; 2 - sealing ring of the flange of the main cylinder; 3 - a cup of the amplifier case; 4 - adjusting bolt; 5 - rod seal; 6 - diaphragm return spring; 7 - amplifier pin; 8 - sealing case; 9 - amplifier case; 10 - diaphragm; 11 - amplifier housing cover; 12 - piston; 13 - protective cover of the valve body; 14 - air filter; 15 - pusher; 16 - pusher return spring; 17 - valve spring; 18 - valve; 19 - valve body bushing; 20 - stock buffer; 21 - valve body; A - vacuum chamber; B - atmospheric chamber; C, D - channels.
With the brake pedal stopped in the middle of its travel, start the engine. With a working vacuum booster, the brake pedal after starting the engine should «go ahead».
If the pedal «does not move forward», check the fastening of the hose tip, the condition and fastening of the tip flange in the amplifier, the hose to the tip and the engine inlet pipe fitting, since loosening or damage to the fastening sharply reduces the vacuum in cavity A and the efficiency of the amplifier.
In the event of spontaneous braking of the car, check the vacuum booster for leaks with the engine running, first with the stationary brake pedal released and then pressed. «Suction» protective cap 13 to the shank of the valve body and the hiss of sucked air indicates insufficient tightness of the amplifier. In these cases, replace the vacuum booster.