0318395 JOHNSON VALVE, Check

Measurement of Pressure in Inlet Manifold
The efficiency of an engine can be checked by making a comparison of the pressure in the inlet manifold with the information in the Technical Marketing Information (TMI).This test is used when there is a decrease of horsepower from the engine, yet there is no actual sign of a problem with the engine.The correct pressure for the inlet manifold is also given in the Technical Marketing Information (TMI), "Fuel Setting and Related Information". These standards are established under the following conditions:
96 kPa (29 Inches Hg) dry barometric pressure.
29°C (85°F) outside air temperature
35 API rated fuelAny change from these conditions can change the pressure in the inlet manifold. The outside air may have a higher temperature and a lower barometric pressure than the values that are given above. This will cause a lower inlet manifold pressure measurement than the pressure in the TMI. Outside air that has both a lower temperature and a higher barometric pressure will cause a higher inlet manifold pressure measurement.A difference in fuel density will change horsepower (stall speed) and boost. If the fuel is rated above 35 API, the pressure in the inlet manifold can be less than the pressure that appears in the TMI. If the fuel is rated below 35 API, the pressure in the inlet manifold can be more than the pressure that appears in the TMI. BE SURE THAT THE AIR INLET OR THE EXHAUST DOES NOT HAVE A RESTRICTION WHEN YOU ARE MAKING A CHECK OF THE PRESSURE.Use 1U-5470 Engine Pressure Group to check the pressure in the inlet manifold.Remove the plug on the aftercooler housing in order to measure inlet manifold pressure.
Illustration 1 g00293196
1U-5470 Engine Pressure Group This tool group has a gauge to read pressure in the inlet manifold. Refer to Special Instruction, SEHS8524 for the operation of this tool group.Turbocharger
Inspect the bearing of the turbocharger if any unusual sound or vibration is noticed.A quick check of the bearing condition can be made without disassembling the turbocharger. This can be done by removing the piping from the turbocharger and inspecting the following items.
The compressor impeller
The turbine wheel
The compressor coverRotate the compressor and the turbine wheel assembly by hand and observe by feeling excess end play. The rotating assembly should rotate freely. There should be no rubbing or binding of the rotating assembly. If there is any indication of the impeller rubbing the compressor cover or the turbine wheel rubbing the turbine housing, replace the turbocharger with a new or rebuilt turbocharger.
Illustration 2 g00320945
Checking turbocharger rotating assembly end play (typical example)End play is checked with a dial indicator. Attach a dial indicator with the indicator point on the end of the shaft. Move the shaft from end to end. Make a note of the total indicator reading.If the end play is more than the maximum end play, rebuild the turbocharger or replace the turbocharger. End play that is less than the minimum could indicate that there is carbon build up on the turbine wheel. The turbocharger should be disassembled for cleaning and inspection.A more reliable check of the bearing conditions can be made only when the turbocharger is disassembled. The bearings, the shaft journal, and the housing bore diameters can actually be measured.Note: Do not cock the shaft. This could result in a false reading.Measurement of Exhaust Temperature
Table 1
Tools Needed    
Part Number     Part Name     Quantity    
123-6700     Laser Infrared Thermometer     1    Use the 123-6700 Infrared Thermometer to check this exhaust temperature. You can find operating instructions and maintenance instructions inside the Operator's Manual, NEHS0630, "123-6700 Infrared Thermometer II with Laser Sighting".Crankcase (Crankshaft Compartment) Pressure
Table 2
Tools Needed    
Part Number     Part Name     Quantity    
8T-2700     Blowby/Air Flow Indicator     1    Pistons or rings that have damage can be the cause of too much pressure in the crankcase. This condition will cause the engine to run rough. There will be more than the normal amount of fumes rising from the crankcase breather. This crankcase pressure can also cause the element for the crankcase breather to have a restriction in a very short time. This crankcase pressure can also be the cause of any oil leakage at the gaskets and at the seals. These areas would not normally have leakage.Note: The electronic service tool can be used to measure crankcase pressure.
Illustration 3 g00286269
8T-2700 Blowby/Air Flow Indicator The 8T-2700 Blowby/Air Flow Indicator checks the amount of blowby. See Special Instructions, SEHS8712 for more information on using this tool.Compression
An engine that runs roughly can have a leak at the valves. An engine that runs roughly can also have valves that need an adjustment. Remove the head and inspect the valves and valve seats. This is necessary to find those small defects that do not normally cause a problem. Repairs of these problems are normally done when you are reconditioning the engine.Cylinder Head
The cylinder heads consist of three main components that can be removed:
valve seat inserts
valve guides
bridge dowelsWhen any of these components are worn or when these components are damaged, these components can be removed. Refer to Disassembly and Assembly for the replacement of these components.Bridge Adjustment
When the head is disassembled, keep the bridges with the respective cylinders. Adjustment of the bridge will be necessary for the following reasons.
the valves are ground