First, product performance and use: piston pump oil institutions, including two sets of precision coupling: plunger (plunger) + plunger sleeve (barrel) constitute a plunger (plunger and barrel assembly) (Figure 5-11) , a delivery valve (delivery valve) and the oil valve seat (Delivery valve seat) outlet valve parts the (Delivery Valve assembly plunger and plunger sleeve is a pair of precision coupling can not be interchanged after pairing grinding requirements high accuracy and finish and good abrasion resistance, the radial clearance of 0.002 ~ 0.003mm plunger head cylindrical surface of the cut, and through the radial bore, the axial bore communicating with the top of the chute, and its purpose is to the change cycle fuel supply; the plunger put the system into the back to the hole, with the low pressure oil pump body cavity, the plunger set into the pump upper body, the application of positioning screw positioning plunger head chute position different, change the amount of oil the oil valve and the oil valve seat is a sophisticated dual pairing after grinding are not interchangeable, with the gap to 0.01mm oil valve is a check valve, spring pressure, the valve upper conical seat surface and tight with its role in the stop for the upper end of the high pressure tubing and plunger isolated from the cavity to prevent oil from flowing back into the fuel injection pump high pressure tubing out the valve lower was cross-sectional, both oriented, but also by diesel out the valve cone has a small cylindrical surface, called Decompression ring, and its role in the end of the oil, the oil in the high pressure tubing pressure decreased rapidly to avoid of the holes drip phenomenon quickly increases, pressure decreases rapidly Minting quickly when the annulus falls within the seat of the upper volume.