Engine damage

A.: Which of the several causes of ignition failures is most

likely to occur?

В.: Failure of the fuel supply is the most common cause, for the reason that the fuel pump is very sensitive to the presence of air and unless great care has been exercised in clearing air out of the fuel lines, the pump will not deliver oil to the injection valves. This is especially true after the fuel lines or pump have been opened up for any reason.

A.: How is air cleared out of the fuel lines?

В.: Most installations include a by-pass valve in each fuel oil discharge line, adjacent to the injection valve. By opening these valves and operating the hand pumps on the fuel measur­ing pump, oil is forced through the pump and pipe line and out through the by-passes, carrying the air with it. When only oil flows from the by-passes the valves are closed and a few strokes given to the hand pumps to force some oil into the injection

valves.

A.: How is the compression pressure measured?

В.: With the indicator, cutting out one cylinder at a time and indicating that cylinder while the rest of the cylinders operate on fuel or starting air. Both methods should be used in order to determine the difference in compression with hot cylinders and with cold.

A.: How is the compression pressure adjusted?

В.: By decreasing or increasing the linear clearance between piston and cylinder head. This is usually done by increasing or reducing the thickness of shims under the foot of the connecting rod.

A.: What are the principal sources of knocks in the Diesel

engine?

В.: The large bearings, the valve gear, or the interior of the cylinders. Bearing knocks are caused by too much clearance. Valve gear knocks may be caused by excessive roller clearance, worn or broken rollers, or sticking valve stems. Knocks inside the cylinder are caused by too early injection, excessive lift of air injection valve at low speed, injection air pressure too high, or stuck piston rings.

A.: How is the separation of the two halves of the box usually obtained?

В.: By placing sheet metal shims between the abutting sur­faces.

A.: How is bearing clearance usually measured?

В.: By placing strips of soft lead wire in the bearing and setting up the bolts. The thickness to which the lead wire is mashed will be equal to the clearance.

A.: How is a bearing refitted?

В.: By scraping the bearing surface of the boxes with steel scrapers until all the high spots are removed and even contact is obtained between bearing and boxes.

6. Lesson 6. Cylinder heads

Notes:

1) . . . and as such suffers most from heat troubles.	... и, будучи таковым, больше всего претерпевает аварии, связанные с нагревом.
2) ... but the former is pre­ferred ....	. . . но предпочтение отдается первой (газовой сварке) ...
3) ... as is usually the case…	. . . как обычно бывает . . .
4) . . . in years gone by . . .	. . . в .прошедшие годы . . .
1) ... that they may be dis­missed without discussion.	. . . что о них можно и не гово­рить.
2) . . . may be said to be non­existent ...	. . . можно сказать, что не су­ществуют ...
3) welding procedure has been developed to the point ...	Методы сварки достигли тако­го совершенства ...
4) ... where most cracked pistons can be salvaged at a cost substantially less than the price of a new one.	… что большинство поршней с трещинами можно восста­новить, при этом затраты оказываются значительно меньше стоимости нового поршня.

The head is usually the most complicated casting on the en­gine, and as such suffers most from heat troubles. The usual head repair is welding of cracks. Both oxyacetylene and electric welding are used, but the former is preferred if the location of the crack will permit its use. If the crack is near the outer edge of the head, where expansion and contraction stresses can be accommo­dated, gas welding can be used, but if the crack is near the centre of the head or surrounded by unsymmetrical masses of metal, as is usually the case, electric welding must be resorted to. To make a successful head repair, electric welding must be done very skillfully and studding employed.