3H6-04000-3 Tohatsu FUEL PUMP

Environmental Factors
Extreme Ambient Temperatures
Extended operation in environments that are extremely cold or hot can damage components. Valve components can be damaged by carbon buildup if the engine is frequently started and stopped in very cold temperatures. Extremely hot inlet air reduces the performance capabilities of the engine.Note: See this Operation and Maintenance Manual, "Cold Weather Operation" topic (Operation Section), or see Supplement, SEBU5898, "Cold Weather Recommendations".Cleanliness
Unless the equipment is cleaned regularly, extended operation in a dirty environment and in a dusty environment can damage components. Built up mud, dirt, and dust can encase components. This can make maintenance difficult. The buildup can contain corrosive chemicals. Corrosive chemicals and salt can damage some components.Improper Operating Procedures
Extended operation at low idle
Minimum cool down periods after high load factor operation
Operating the engine beyond the guidelines for the engine rating
Operating the engine at loads that are greater than the rated load
Operating the engine at speeds that are greater than the rated speed
Use of the engine for an application that is not approvedImproper Maintenance Practices
Extension of maintenance intervals
Not using recommended fuel, lubricants, and antifreeze/coolantOverhaul Information
An overhaul is replacing the major worn components of the engine. An overhaul interval is a maintenance interval that is planned. The engine is rebuilt with certain rebuilt parts or new parts that replace the worn parts.An overhaul also includes the following maintenance:
Inspection of all the parts that are visible during the disassembly
Replacement of the seals and gaskets that are removed
Cleaning of the internal passages of the engine and the engine blockMost owners will save money by overhauling the engine at the intervals that are recommended in this Operation and Maintenance Manual. Consider the graph in Illustration 1.
Illustration 1 g00745964
(Y) Cost
(X) Time
(1) Cost of maintenance and repair that is planned
(2) Cost of maintenance and repair that is not planned In Illustration 1, line (1) represents the maintenance and repair costs for an owner that followed the recommendations for inspection, maintenance, and repair. The peaks represent overhauls.Line (2) represents the maintenance and repair costs for an owner that chose to operate beyond the recommended intervals. The initial cost of the “repair-after-failure” philosophy is lower. Also, the first overhaul was delayed. However, the peaks are significantly higher than the peaks for the customer that used the “repair-before-failure” philosophy .The higher peaks result from two key factors:
Delaying an overhaul until a breakdown increases the chance of a catastrophic failure. This type of failure requires more parts, labor, and cleanup.
Excessive wear means that fewer components will be reusable. More labor may be required for salvage or repair of the components.When all of the costs are considered, “repair-before-failure” is the least expensive alternative for most components and engines.It is not practical to wait until the engine exhibits symptoms of excessive wear or failure. It is not less costly to wait. A planned overhaul before failure may be the best value for the following reasons:
Costly unplanned downtime can be avoided.
Many original parts can be reused according to the guidelines for reusable parts.
The service life of the engine can be extended without the risk of a major catastrophe due to engine failure.
Achieve the best cost/value relationship per hour of extended service life.Overhaul Intervals
Some factors that are important for determining the overhaul intervals include the following considerations:
Performance of preventive maintenance
Use of recommended lubricants
Use of recommended coolants
Use of recommended fuels
Proper installation
Operating conditions
Operation within acceptable limits
Engine load
Engine speedGenerally, engines that are operated at a reduced load and/or speed achieve more service life before an overhaul. However, this is for engines that are properly operated and maintained.Other factors must also be considered for determining a major overhaul:
The total amount of fuel consumption
The service hours of the engine
An increase of oil consumption
An increase of crankcase blowby
The wear metal analysis of the lube oil
An increase in the levels of noise and vibrationAn increase of wear metals in the lube oil indicates that the bearings and the surfaces that wear may need to be serviced. An increase in the levels of noise and vibration indicates that rotating parts require service.Note: It is possible for oil analysis to indicate a decrease of wear metals in the lube oil. The cylinder liners may be worn so that polishing of the bore occurs. Also, the increased use of lube oil will dilute the wear metals.Monitor the engine as the engine accumulates service hours. Consult your Caterpillar dealer about scheduling a major overhaul.Note: The driven equipment may also require service when the engine is overhauled. Refer to the literature that is provided by the OEM of the driven equipment.Using Fuel Consumption For Calculating the Overhaul Intervals
Experience has shown that maintenance intervals are most accurately based on fuel consumption. Fuel consumption corresponds more accurately to the engine load. Tables 1, 2, and 3 list average ranges of fuel consumption for a load factor of approximately 60 percent.
Table 1
Maintenance Intervals for Overhaul
Fuel Consumption for 3508 and 3508B Engines
Top End Overhaul 976,000 L (257,500 US gal)
Second Top End Overhaul 1,952,000 L (515,000 US gal)
Major overhaul 2,928,000 L (772,500 US gal)
Table 2
Maintenance Intervals for Overhaul
Fuel Consumption for 3512 and 3512B Engines
Top End Overhaul 1,460,000 L (385,000 US gal)
Second Top End Overhaul 2,920,000 L (770,000 US gal)
Major Overhaul 4,380,000 L (1,155,000 US gal)