Ch. 12 Preventative Maintenance and Troubleshooting Feb 23 5:03 PM 1
Why PM? preventive maintenance certain maintenance tasks must be performed regularly to keep an engine working properly helps premature engine wear Feb 23 5:15 PM 2
Keeping Engines Clean cleaning a small air cooled engine periodically can prevent overheating If cooling fins are insulated by dirt, leaves, and/or grass clippings, engine parts will receive most of combustion heat Feb 23 5:18 PM 3
Parts (overheated) Will expand, distort, and possibly seize Clean all surfaces to the bare metal Feb 23 5:19 PM 4
Methods for Cleaning blow debris from fins with compressed air and use a cleaning solvent Scrape dirty areas with a piece of wood and wipe them off with a clean cloth Feb 23 5:21 PM 5
Checking Oil level and condition crankcase oil in four cycle engines should be checked periodically(each time fuel is added) Use the type of visocity grade of oil recommended by manufacturer Feb 23 5:23 PM 6
Checking the Oil withdraw dipstick, wipe it dry Reinsert the dipstick, withdraw and observe oil level All have low(add) and Full Mark Feb 23 5:30 PM 7
Add Oil if its on LOW Do NOT run the engine if there is oil above the full mark Overfilling will foul plugs and cause the engine to use too much oil Feb 23 5:31 PM 8
Engine Oil dropping at excessive rate Typical causes: External Leaks Worn oil seals around crankshaft Worn Valve Guides Worn piston rings Hot Running Engine Feb 23 5:36 PM 9
When to change oil *New only after a few hours of running to remove any metallic particles from the crankcase After that 10 50 hours of running time Feb 23 5:38 PM 10
Engine Oil does not wear out, always slippery becomes contaminated with dirt particles, soot, sludge, varnish forming materials, metal particles, water, corrosive acids, and gasoline The harm they cause outweighs the lubricating quality of the oil Feb 23 5:42 PM 11
Loaded Oil cannot absorb any more contaminants and still be an effective lubricant when oil becomes loaded, varnish deposits begin to form on the piston and rings and sludge collects in the crankcase Feb 23 5:55 PM 12
Changing Oil Disconnect spark plug Oil drain plug is located at low point on crankcase, remove plug with proper wrench Drain oil, replace plug Change filter(if equipped) Coat o ring with light coat of clean oil, before new filter is put on Pour new engine oil into crankcase, checking levels Start and run engine for a few minutes Feb 23 5:56 PM 13
Mixing Oil and Fuel can seriously damage engines by improper mixing Proper way Pour gasoline into clean container first. Add oil to the gasoline and shake. Add the rest of the gasoline and shake again. Feb 23 6:02 PM 14
Condensation forms in partially filled containers because of temperature changes. During the day it warms up, holds moisture At night, cools and loses water vapor Each night, more water is added to fuel Feb 23 6:06 PM 15
Air cleaner service carb air cleaner should be cleaned before each season of operation a plugged air filter can cause hard starting, loss of power, and spark plug fouling Feb 23 6:12 PM 16
Crankcase breather service should be removed and cleaned periodically remove screws and cover inspect reed valves wash all parts in cleaning solvent Feb 23 6:15 PM 17
Muffler Service Install a new one, check for improved efficiency If designed to be taken apart, diassemble and clean in solvent Feb 23 6:19 PM 18
Water Cooling water and metal produce chemical reactions, rust inhibitor should be added Feb 23 6:20 PM 19
Settlements Scale settling to the bottom may clog passageways of water No circulation will cause hotspots Feb 23 6:21 PM 20
Reverse Flushing(engine blocks, radiators) Disconnect hoses from radiator and block Force clean water in the opposite direction of circulation Flush until water runs clear Feb 23 6:22 PM 21
Salt Water Gearcase removed from water when not in use Rinse engine with freshwater and wipe all lower unit parts with clean, oily cloth Ignition leads and spark plug insulators should be wiped frequently to prevent accumulation of salt residue Feb 23 6:24 PM 22
Storing water cooled engines During winter, antifreeze must be added to the water to protect against freezing (FLORIDA or down south) Or DRAIN completely (tag engine) YOU COULD Crack cylinder block, gearcase, damage water channels and tubes Feb 23 6:27 PM 23
Systematic Troubleshooting Don't take whole engine apart Troubleshooting number of steps you go through to find a problem Basic principles 1.Test easiest things first 2. verify fundamental operating principles Feb 23 6:38 PM 24
Easiest things first Engine won't start? Empty fuel tank? Disconnected spark plug wire? Do not work on carburetor or ignition system until you have made a few basic checks Feb 23 6:40 PM 25
Fundamental Operating Requirements What are they? 1. Proper carburetion 2. Correct ignition system operation 3. Adequate lubrication 4. Sufficient cooling 5. Proper compression Feb 23 6:42 PM 26
Proper Carburetion Clean, fresh fuel must be delivered in the correct proportion with combustion air Feb 23 6:45 PM 27
Correct ignition system operation Strong ignition spark must be precisely timed for best performance and efficiency Feb 23 6:45 PM 28
Adequate Lubrication Proper amount of high quality lubricating oil must reach critical engine components Feb 23 6:48 PM 29
Sufficient Cooling Ample supply of cooling air, must reach engine Feb 23 6:48 PM 30
Proper Compression 30 45 psi minimum for starting and 90 psi minimum for efficient operation and sufficient power Feb 23 6:49 PM 31
Reasoning & Troubleshooting Use reasoning to make troubleshooting attempts at a specific area Feb 23 6:52 PM 32
Check RPM Test maximum idle rpm or governor RPM Tachometer aimed at rotating part(reflective tape), handheld Stroboscope high intensity light, measures rpm Feb 23 6:52 PM 33
Compression Check first test determining the upper major mechanical parts of the engine Procedure: 1. Run engine until its warm 2. Disconnect all drives to the engine 3. Open choke and throttle valves wide 4. Remove the air cleaner 5. Remove spark plug and insert compression gauge 6. Crank the engine as fast as possible to obtain an accurate test Feb 24 7:03 AM 34
Less Compression than suggested? Leaking Cylinder head gasket Warped Cylinder head Worn piston rings Worn Cylinder bore Damaged Piston Burned or warped valves Improper Valve Clearance Broken or weak valve springs Feb 24 7:06 AM 35
Differential Pressure DP test checks the compression of an engine by measuring leakage from the cylinder to the other parts of the engine Designed to detect specific leakages so you don't have to disassemble whole engine Feb 24 7:07 AM 36
Differential Pressure Test 1. Run the engine until it is warmed up to provide uniform lubrication to cylinder walls and rings 2. Remove spark plug wire and spark plug 3. Rotate the engine crankshaft until the piston of the cylinder being tested is at top dead center of the compression stroke. Both valves must be closed. 4. Thread adaptor into spark plug hole 5. Connect adaptor on rubber hose to quick disconnect fitting on tester. 6. Connect an air source of at least 90 psi to the tester adaptor. 7. Slowly adjust the regulated pressure gauge on the left with the regulator knob at 80 psi 8. the right hand gauge indicates the relative pressure of the cylinder being tested Feb 24 7:09 AM 37
Service Information Before starting engine work, look at service manual Manuals provide service procedures Exploded views show assemblies and systems (diassemble and reassemble in correct order) Feb 24 7:17 AM 38
Troubleshooting Charts List common causes and engine troubles along with common remedies (help) Feb 24 7:19 AM 39
Tolerances and Clearances Given in chart form in manuals/bulletins When checking, adjusting spark plug gap, breaker point gap, ignition timing, this chart gives correct dimensions and piston locations When chart shows two dimensions, it must be within range Feb 24 7:19 AM 40
Torque Specifications Necessary to tighten them evenly and according to certain sequence Over tightening will crush gaskets, distort metal Generally, bolts are tightened in a sequence from one side to another Feb 24 7:23 AM 41