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18 November 2018

90.Slide type fuel Injector

November 18, 2018 Posted by AK No comments
The slide type fuel valve is designed for eliminating the sac volume to prevent any fuel oil from entering in combustion chamber without being injected.

The combustion is improved. However this function is assured by the cut off shaft“ which is a
fragile piece requiring a special attention.


The fuel valve consists of a valve head 197, union nut 148 and valve body 124. Fitted within the valve body are non return valve 220 with a combined slide/valve, thrust spindle 232 with spring 256, thrust foot 268, and spindle guide complete 053. 

When the fuel valve is fitted in cylinder cover, the valve parts are tightened together by the pressure from the nuts being transmitted through valve head, non return valve, thrust spindle, and spindle guide complete to the valve body, which is pressed into the tapered bore in the cylinder cover. The union nut keeps valve head and valve body together during dismantling of the fuel valve.

The spindle guide complete 053 consists of spindle guide 077, nozzle 090, thrust piece 016 and cut off shaft 028. The spindle guide is assembled with a press fit. The cut off shaft 028 is pressed against the tapered seat of spindle guide 077 by the action of the spring 256, the spring pressure being transmitted through the slotted thrust foot 268.

The thrust spring determines the opening pressure of the valve. Optionally, an extra disc can be inserted to raise the opening pressure by 20 bar. The non return valve 220 consists of housing, thrust piece, slide and spring. The non return valve is assembled with a press lift.

The slide of the non return valve is pressed by the spring against the tapered valve seat inside the non return valve. In this position the head of the slide uncovers a small bore arranged for circulation purposes in the thrust piece.

The functioning of the Fuel Valve.

Position 1.

The electrical fuel oil circulating pump circulates preheated oil through the fuel pump
and fuel valve. In the fuel valve the oil passes through the central bore of the valve
head and continues to the thrust piece in the non return valve, leaving through the
circulation bore of the latter. Thence the oil is passed through the interior of the valve
body to an outlet pipe on the side of the valve head.


If for some reason, cut off shaft 028 should not close during engine standstill, then
the closed spindle of the non return valve will prevent the circulating pump from
pressing oil through the nozzle, and thus obviate the risk of the engine cylinder being
filled with oil.

Position 2.

When, at the beginning of the delivery stroke, the pressure has risen to about 10 bar,
the force of the spring of the non return valve will be overcome and the spindle
pressed back against the shoulder of the thrust piece.

Position 3.

When the spindle of the non return valve is pressed upwards, the circulation bore of
the thrust piece is closed, and the oil passes the seat of the spindle and enters the
space round cut off shaft 028 in the spindle guide. When the pressure has risen to
the preset opening value of the fuel valve, the spindle is lifted, and oil is forced
through the nozzle into the engine cylinder.


At the termination of the delivery stroke first cut off shaft 028 and then the spindle of
the non return valve will be pressed against their respective seats, the injection of
fuel stops, and oil is again circulated through the valve (position).

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