Fuel priming pump (fig. 1). Piston type, mounted on high pressure pump and driven by camshaft eccentric
Piston 2, spring 3 of the piston are placed in the pump housing 1, resting with one end against the piston, with the other against plug 5, suction 25 and discharge 14 valves, which are pressed against the seats 26 by springs 15.
The cavity of the pump housing, in which the piston moves, is connected by channels to the cavities above the suction and below the discharge valves.
The piston is driven by the pusher 9 through the rod 7.
The roller 13 of the pusher rotates on a floating axle 12, locked from longitudinal movement by two crackers 11.
At the same time, the crackers, moving in the grooves of the body 1, protect the pusher from turning.
Spring 8, resting against sleeve 6, presses the pusher against the eccentric.
The rod 7 moves in the guide sleeve 6, which is wrapped with a special adhesive in the pump housing. The stem and sleeve are a precision pair.
The fuel priming pump is equipped with a manual priming pump.
The seal between the body 18 of the pump cylinder and the cylinder 19 is a rubber gasket 23, which, when the handle 22 is screwed onto the cylinder, simultaneously seals the gap between the piston 20 and the body 18.
Repair of the fuel priming pump
The fuel priming pump (see Fig. 1) is disassembled in the following sequence:
- - unscrew the hand pump assembly and valve plug;
- - remove the valves and their springs;
- - unscrew the spring plug and remove the piston spring and piston;
- - remove the retaining ring, remove the pusher and the pusher spring.
When disassembling and assembling the fuel priming pump, remember that the piston and housing of the priming pump, as well as the piston and cylinder of the hand pump, are precisely matched pairs and cannot be dismantled.
Mechanical breakage of parts and thread stripping are not allowed.
The body of the fuel priming pump must not have breakages, cracks or damage to the threads for the fuel line bolts.
The allowable clearance between the casing and the pump piston must not exceed 0.18 mm.
The gap in the connection between the pump housing and the pusher should not exceed 0.2 mm.
The piston of the fuel pump must not be more than 0.25 mm deep from the pusher rod.
The pump valve with the end face of the seat must ensure the tightness of the connection.
When evaluating the condition of other parts, remember that the gap should not exceed:
- - between the roller axis and the piston pusher 0.15 mm;
- - between the pusher roller and the roller axis 0.28 mm;
- - between the cylinder and the piston of the hand pump 0.05 mm.
Special attention must be paid to the condition of the stem-sleeve assembly. The gap in the specified connection should not exceed 0.014 mm.
The density of the specified pair is checked by the time of pressure drop from 150--120 kgf / cm2 as a result of the outflow of fuel through the gap between the bushing and the rod.
Tests should be carried out on filtered summer diesel fuel or on mixtures thereof with aviation or spindle oil or tractor kerosene.
The viscosity of the mixture at a temperature of 20˚c should be 1.4 -1.5 conventional degrees. The time for the pressure to fall to the specified limits must be at least 1 minute.
At a lower density, the pair is replaced.
The fuel priming pump is assembled in the reverse order of disassembly.
If a precision stem-bushing assembly is being replaced, the thread surface and end face in the pump housing must be thoroughly cleaned of any adhesive residue on which the stem bushing was removed.
The new sleeve must be installed in the pump housing with an epoxy based adhesive.
To ensure the strength and tightness of the connection with glue, thoroughly cleaned contact surfaces of the pump housing and the rod bushing must be degreased with gasoline or other liquid beforehand.
The stem sleeve is tightened with a torque of 1 kgcm.
After tightening, check the ease of movement of the rod along the sleeve.
If the movement of the stem is difficult, you need to slightly loosen the sleeve.