0114800 JOHNSON FUEL CAP & AIR VENT ASSY.

2. Measuring Compression Pressure
2.1 Preparation for InspectionPerform the following checks before starting the inspection.(1) Make sure the engine oil, air cleaner, starter, and battery are normal.(2) Make sure the engine is warm.2.2 Inspection(1) Move the control lever to the stop position.(2) Remove all glow plugs, then connect the Compression Gauge Adapter (ST333060) and compression gauge to the cylinder whose compression pressure is to be checked.(3) Crank the engine using the starter until the needle of the compression gauge stops moving, then read the pressure indication.(4) If the measurement is lower than the specified limit, perform an overhaul.
(a) Measure the compression pressure of every cylinder. Measuring the compression pressures of two or three cylinders and simply assuming the compression pressures of the other cylinders is dangerous.(b) The compression pressure varies with the engine speed, so it is important to take all measurements with the same engine speed.
Unit: MPa {kgf/cm2} (psi) Take measurements with an engine speed of 240 min-1.
Compression gauge and adapter
Measuring compression pressure
(a) It is important to measure compression pressures regularly and to keep track of changes in them.(b) During the engine's run-in period and after an overhaul, the compression pressures will increase slightly as the piston rings, valve seats, and other parts fit snugly in position. The pressures will then decrease as parts wear.
3. Troubleshooting
3.1 OverviewDiesel-engine fault symptoms tend to have multiple causes, which influence each other. Consequently, it is often difficult to locate a fault based on the symptoms. Particular care is required when diagnosing faults related to the injection pump, injectors, and compression pressures since such faults may produce the same symptoms.For the above-mentioned reasons, the inspection sequences in the troubleshooting charts on the following pages start with items where the likelihood of a fault is greatest with items that are easiest to inspect.Owing to their structure and combustion method, diesel engines exhibit the characteristics listed below. Familiarize yourself with these characteristics before performing troubleshooting operations.* Distinctive combustion noise (diesel knock) is emitted during normal operation.* Some black smoke is emitted during high-load operation.* Torque vibration is significant owing to the high compression pressure and high torque.* Slight hunting occurs during rapid deceleration.* Some white smoke is emitted immediately after startup when the engine is cold.
(a) The injection pump cannot be adjusted without a pump tester. Do not attempt to adjust or disassemble the injection pump during troubleshooting operations.(b) To check the combustion conditions in each cylinder, undo the cylinders' injection pipes one at a time (undoing an injection pipe stops injection in that cylinder) and compare the resulting decreases in engine speed. Retighten each injection pipe before undoing the next one.
3.2 Difficult Starting(1) Items to CheckBefore performing inspections, check for the following problems:* Clogged air cleaner element* Coagulation of engine oil* Inferior fuel* Low cranking speed(2) Inspection 3.3 KnockingDiesel engines emit a distinctive knocking sound owing to their combustion method. This sound is normal unless it is excessive.(1) Items to CheckBefore performing inspections, check for the following problems:* Clogged air cleaner element* Inferior fuel(2) Inspection 3.4 Overheating(1) Items to CheckBefore performing inspections, check for the following problems:* Low coolant level; coolant leakage* Loose fan belt* Clogged radiator fins(2) Inspection In many cases, overheating is caused by poor matching of the engine and machine. If the engine overheats despite being free of faults, measure the ambient temperature and the coolant temperature with the engine loaded, i.e., with the thermostat fully open, and calculate the difference between the two temperatures. If the difference is greater than 60°C (108°F), problems in areas outside the engine should be investigated.3.5 Excessive Black Smoke(1) Items to CheckBefore performing inspections, check for the following problems:* Clogged air cleaner element* Inferior fuel(2) Inspection 3.6 Irregular idling(1) Items to CheckBefore performing inspections, check for the following problems:* Problems in engine control system* Incorrect engine oil viscosity* Inferior fuel(2) Inspection 3.7 Low Output(1) Items to CheckBefore performing inspections, check for the following problems:* Seized parts in engine* Excessively high engine oil viscosity* Inferior fuel* Clogged air cleaner element* Clogged exhaust muffler* Faulty power takeoff(2) Inspection 3.8 Troubleshooting with Starter With overrunning problems, symptoms include burns of clutch pinion bearing in addition to the symptoms shown above and irrespective of the problem types.