0115528 JOHNSON SPRING COVER

Air Induction And Exhaust System
Restriction Of Air Inlet And Exhaust
Engine horsepower and efficiency will be reduced if either the air inlet or exhaust system becomes restricted.The air cleaner should not restrict air flow more than 30" (762 mm) of water difference in pressure.Exhaust back pressure (pressure difference measured between the turbocharger outlet elbow tap and the ambient air) should be no more than 15" (381 mm) of water, difference in pressure.Measuring Inlet Manifold
By checking inlet manifold pressure, and comparing that pressure with the RACK SETTING INFORMATION, one can determine if an engine is operating efficiently. This test should be used if engine horsepower seems to be too low, yet no specific symptom of engine trouble is apparent.Inlet manifold pressures in the RACK SETTING INFORMATION are recorded under specific operating conditions: 29.4 inches (746,76 mm) of mercury barometric pressure, 85° F. (29.4° C.) ambient temperature and 35 API rated fuel. Any deviation from these conditions can affect the inlet manifold pressure. Ambient air which is denser than that at 85°F./29.4 inches (29.4°C./746,76 mm) of mercury, can cause a slightly higher horsepower and inlet manifold pressure reading than listed in the RACK SETTING INFORMATION. If the ambient air is less dense, the horsepower and inlet manifold pressure rating can be slightly lower. Fuel density (API gravity rating) also affects the horsepower and inlet manifold pressure. If the fuel is rated above the standard 35 API gravity rating, the inlet manifold pressure can be slightly less than the value given in the RACK SETTING INFORMATION. If the fuel is rated below the standard rating, the inlet manifold pressure can be slightly more. BE SURE THE AIR INLET AND EXHAUST ARE NOT RESTRICTED WHEN CHECKING INLET MANIFOLD PRESSURE.The components in a 4S6553 Instrument Group provide a means of reading engine RPM and inlet manifold pressure simultaneously. This group contains an instantaneous reading tachometer and a gauge for reading inlet manifold pressure. Instructions (FE036044) included with this group, explain the testing procedure.Crankcase Pressure
Excessive crankcase pressure can be a result of combustion gas leaking past broken or damaged pistons and/or piston rings. This condition will usually be accompanied by irregular engine operation and excess fumes from crankcase breather opening. This pressure can cause the breather element to become restricted in an unusually short time. In addition, it can cause engine oil to leak past gaskets and seals that would function properly under normal conditions.Testing Pressure Ratio Regulator-3S860
Before making pressure tests, see that the exhaust bypass valve moves in the base without binding.1. Use a suitable adapter bolted to the high pressure flange to mount the assembly so the valve axis is in a horizontal position on testing stand described in FE034610. The high pressure flange is identified as the flange having greatest distance between mounting bolt hole centers.2. Measure and record dimension (A).3. Regulate boost pressure until the reading on the boost pressure gauge is equal to the initial testing pressure of 1.60 times barometric pressure.4. Remeasure dimension (A). Dimension (A) should decrease less than .30 in. (7,62 mm).5. Regulate boost pressure until the reading on the boost pressure gauge is equal to the secondary testing pressure of 1.64 times barometric pressure.
PRESSURE RATIO REGULATOR
1-Exhaust bypass valve. A-Dimension between surface of base to valve head.6. Measure dimension (A). Dimension (A) should decrease more than .30 in. (7,62 mm).
Do not exceed the secondary test pressure.
Camshaft Installation
1. Extreme caution should be exercised to be sure that all the camshaft followers are adjusted to provide maximum clearance before installation of the camshafts.2. Rotate the crankshaft until No. 1 cylinder is at top center on the compression stroke.3. Position the camshaft phasing gear timing marks (1) together and in a horizontal plane as shown.
CAMSHAFT PHASING GEARS
1-Timing marks.4. Install the camshaft assembly.5. Install the cam driveshaft with the blind spline on top.6. Install the glow plug lead assembly and connect the leads to the glow plugs.7. Adjust the valve clearance.Fuel System
The most likely causes for faulty fuel injection performance are:1. Air in the fuel system.2. Low fuel supply.3. Water in the fuel.4. Clogged fuel filters.5. Insufficient fuel transfer pump pressure.If these conditions are checked and corrected and the engine still does not perform properly, the fuel injection equipment should be checked.Checking Fuel Injection Equipment
Before removing a fuel injection pump or valve for testing from an engine that is missing or puffing black smoke at the exhaust, a simple check can be made to determine which cylinder is causing the difficulty. With the engine running at a speed which makes the defect most pronounced, momentarily loosen the fuel line nut on the injection pump sufficiently to "cut out" the cylinder. Check each cylinder in the same manner. If one is found where loosening makes no difference in the irregular operation of the engine or causes puffing of black smoke at exhaust to cease, probably the pump and valve, for only that cylinder, need be tested.Fuel Injection Valve
The function of the fuel injection valves is to inject and atomize the fuel from the fuel injection pumps into the precombustion chambers. Irregular engine operation and smoking may be caused by an improperly operating injection valve.
FUEL INJECTION VALVE CROSS SECTION
1-Nut. 2-Body. 3-Fuel line assembly. 4-Nozzle assembly.The fuel injection valve is installed in the precombustion chamber. The valve assembly consists of body (2), nut (1), and nozzle assembly (4).Only the nozzle assembly need be replaced.Nozzle assembly (4) and body (2) are held in place by nut (1). The nozzle assembly is only finger-tight on the body. Check the seats of both the nozzle and the precombustion chamber.It is important to maintain the nozzle retaining nut torque to 105 5 lb. ft. (14,5 0,7 mkg). EXCESSIVE TORQUE will damage the nozzle. LESS TORQUE will allow the nozzle to leak and may cause the nozzle case to bulge or split.Checking Fuel Injection Valve
The condition of a capsule-type nozzle assembly can be tested out of the engine on the Caterpillar Diesel Fuel Injection Test Apparatus. The spray characteristics, valve unseating pressure, and the