PUMP GP-GEAR 10R3819 - Caterpillar

1. Determining When To Overhaul The Engine
Generally, when to overhaul the engine is to be determined by taking into consideration a drop in compression pressure as well as an increase in lubricating oil consumption and excessive blowby gases.Low power or loss of power, increase in fuel consumption, drop in lubricating oil pressure, hard starting and excessive abnormal noise are also engine troubles. These troubles, however, are not always the result of low compression pressure and give no valid reason for overhauling the engine.The engine develops troubles of widely different varieties when the compression pressure drops in it. Following are the typical troubles caused by this compression pressure failure:(a) Low power or loss of power(b) Increase in fuel consumption(c) Increase in lubricating oil consumption(d) Excessive blowby through breather due to worn cylinder sleeves, pistons, etc.(e) Excessive blowby due to poor seating of worn inlet and exhaust valves(f) Hard starting(g) Excessive abnormal noiseIn most cases, these troubles occur concurrently. Some of them are directly caused by low compression pressure, but others are not. Among the troubles listed above, (b) and (f) are caused by a fuel injection pump improperly adjusted with respect to injection quantity or injection timing, worn injection pump plungers, faulty injection nozzles, or poor care of the battery, starter and alternator.The trouble to be considered as the most valid reason for overhauling the engine is (d) Excessive blowby through breather due to worn cylinder sleeves, pistons, etc.; in actually determining when to overhaul the engine, it is reasonable to take this trouble into consideration in conjunction with the other troubles.2. Testing The Compression Pressure
(1) Remove the injection nozzle from a cylinder on which the compression pressure is to be measured.(2) Attach the gauge adaptor (36791-00100) to the cylinder, and connect the compression gauge to the adaptor.(3) Crank the engine by means of the starter, and read the compression gauge indication when the engine begins to run at the specified speed.(4) If the compression pressure is lower than the Repair limit, overhaul the engine.
(a) Be sure to measure the compression pressure on all cylinders. It is not a good practice to measure the compression pressure on two or three cylinders and judge the compression pressure of the remaining cylinders therefrom.(b) The compression pressure varies with change of engine rpm. This makes it necessary to check engine rpm at the time of measuring the compression pressure.
Measure the compression pressure with the engine running at 300 rpm.
(a) It is important to measure the compression pressure at periodical intervals to obtain the data on the gradual change of the pressure.(b) The compression pressure would be slightly higher than the Assembly standard in a new or overhauled engine owing to breaking-in of the piston rings, valve seats, etc. It drops as the engine parts wear down.