Compression test
| PART NUMBER | TOOL NAME |
| HD-33223-1 | CYLINDER COMPRESSION GAUGE |
Combustion chamber leakage may cause performance issues. A compression test can help determine the source of cylinder leakage.
Note. Note gauge readings at the end of the first and last compression strokes.
1. Perform compression test on front cylinder.
- a. Run engine to normal operating temperature.
- b. Remove spark plugs. See Replace spark plugs.
- c. Connect CYLINDER COMPRESSION GAUGE (Part # HD-33223-1) to front cylinder.
- d. Verify transmission is in NEUTRAL.
- e. Twist on and hold throttle to fully open throttle plate.
- f. Crank engine continuously through five to seven full compression strokes. Record test results.
2. Perform compression test on rear cylinder.
3. Review test results.
- a. Compare to specifications. Refer to Table 4-15.
- b. Final compression reading should have no more than a ten percent variance between front and rear cylinders.
- c. If compression of a cylinder does not fall within its upper and lower limits, refer to Table 4-16.
4. Verify worn piston rings.
- a. Inject approximately 15 ml (0.5 oz) engine oil into each cylinder.
- b. Repeat the compression tests on both cylinders. Readings that are considerably higher during the second test indicate worn piston rings
5. Verify that throttle plate is in the closed position.
6. Install spark plugs. See Replace spark plugs.
Table 4-16. Compression Test Results
| TEST RESULTS | DIAGNOSIS |
| Compression low on first stroke, builds up on the following strokes, but does not reach normal. Improves considerably when oil is added to cylinder. | Ring trouble |
| Compression low on first stroke, does not build up much on following strokes. Does not improve considerably with the addition of oil. Verify valve lash. | Valve trouble |
| Same results as valve trouble. | Head gasket leak |
Smoking engine or high oil consumption
Perform the Compression Test. See Troubleshooting of engine, Compression Test.
If engine is consuming oil, add engine oil dye and run engine prior to disassembly. This will help determine if porosity is present in the cylinder head or exhaust port cavity.
If further testing is needed, remove the suspect cylinder heads and inspect the following:
Check Prior to Cylinder Head Removal:
- Crankcase overfilled
- Oil carryover
- Breather hose restricted
- Restricted oil filter
Check After Cylinder Head Removal:
- Valve guide seals
- Valve guide to valve stem clearance
- Gasket surface of both head and cylinder
- Cylinder head casting's porosity allowing oil to drain into combustion chamber
- Piston/ring failure
Oil pressure test
1. Perform oil pressure check. See Oil pressure switch.
2. Start engine and test oil pressure switch for proper operation. Check oil pressure switch for leaks.
Table 4-17. Troubleshooting Oil Pressure Signal Lamp
| OIL PRESSURE INDICATOR LAMP | PROBABLE CAUSES |
| Stays on at speeds above idle | Empty oil reservoir Grounded oil switch wire Malfunctioning signal switch Diluted oil Malfunctioning or improperly installed pressure relief valve Oil strainer clogged |
| Flickers at idle | Incorrect idle speed Malfunctioning or improperly installed pressure relief valve |
| Does not illuminate when ignition is turned on (prior to engine start) | Malfunctioning signal switch Malfunction in wiring Burned out signal bulb Dead battery |
Table 4-18. Troubleshooting: Engine Noise or Vibration
| CONDITION | CHECK | REMEDY |
| Engine vibrates | Loose engine mounts | Secure engine mounts. |
| Worn bearing or bearing seat | Replace bearing or worn component. | |
| Incorrect balancer shaft timing | Properly set balancer shaft timing. | |
| Excessive noise while cranking | Worn starter motor teeth, friction clutch or freewheel gear | Replace starter motor, friction clutch or freewheel gear. |
| Inoperative or damaged chain tensioner | Noise disappears after engine started when oil pressure is available. | |
| Excessive noise from valve train area | Valve clearance below specification | Adjust valve clearance. |
| Inoperative or damaged chain tensioner | Replace chain tensioner. | |
| Worn camshaft or camshaft brackets | Replace camshafts and/or brackets. | |
| Worn camshaft drive or camshaft sprockets and camshaft gears loose | Tighten or replace camshaft gears or camshaft sprocket. | |
| Worn camshaft chain, chain guide or chain tension guide | Replace camshaft chain, chain guide or chain tension guide. | |
| Excessive noise from piston area | Worn piston or cylinder | Replace piston or cylinder. |
| Worn piston pin bore or piston pin | Replace piston and/or piston pin. | |
| Worn piston rings grooves or damaged piston rings | Replace piston and/or piston rings. |
Table 4-19. Troubleshooting: Engine Does Not Crank, Cranks But Does Not Start or Starts Hard
| CONDITION | CHECK | REMEDY |
| Engine cranks but does not start or starts hard | Loose spark plugs | Tighten spark plugs. |
| Incorrect or worn spark plugs | Replace spark plugs. | |
| Fouled or wet spark plugs | Clean or replace spark plugs. | |
| Discharged battery, cranking rpm too low | Check/replace battery, connections and charging system. | |
| Inadequate fuel supply | Check fuel level in tank, add if necessary. Check/replace fuel filter, fuel supply lines, fuel pump, fuel pressure sensor and fuel injectors. | |
| Improper valve clearance | Adjust valve clearance. | |
| Incorrect valve timing | Adjust position of camshaft gears and camshaft sprocket. | |
| Inoperative or damaged ignition coil(s) | Replace ignition coil(s). | |
| Inoperative or damaged CKP or ECM | Check/replace CKP and/or ECM. | |
| Leaking cylinder head gasket(s) | Replace cylinder head gasket(s). | |
| Valve and/or valve guides worn or imperfect valve seat | Replace valves, rework valve seats or replace cylinder head if necessary. | |
| Worn piston rings and/or cylinder bore | Replace piston rings and cylinders if necessary. | |
| Improper viscosity oil for ambient temperature conditions | Change engine oil and refill with correct viscosity oil for ambient temperature. |
Table 4-20. Troubleshooting: Engine Performance
| CONDITION | CHECK | REMEDY |
| Engine runs irregularly at idle | Excessive spark plug electrode gap | Set gap properly or replace spark plugs. |
| Valve clearance below specification | Adjust valve clearance. | |
| Intake air leak | Tighten intake flange, replace gasket or replace intake flange if necessary. | |
| Malfunctioning ignition unit or incorrect ignition timing | Check CKP and ECM, replace if necessary. | |
| Valve and/or valve guides worn or imperfect valve seat | Replace valves, rework valve seats or replace cylinder head if necessary. | |
| Engine runs irregularly at higher speed | Fuel pressure too low | Check fuel pressure sensor, fuel pump and fuel supply. |
| Intake air leak | Tighten intake flange, replace gasket or replace intake flange if necessary. | |
| Worn camshafts | Check and replace if necessary. |
Table 4-20. Troubleshooting: Engine Performance
| CONDITION | CHECK | REMEDY |
| Insufficient engine performance | Intake air leak | Tighten intake flange, replace gasket or replace intake flange if necessary. |
| Incorrect or worn spark plugs | Replace spark plugs. | |
| Improper valve clearance | Adjust valve clearance. | |
| Incorrect valve timing | Adjust position of camshaft gears and camshaft sprocket. | |
| Insufficient ignition voltage | Check/replace ignition coil(s). | |
| Inoperative or damaged CKP or ECM | Check/replace CKP and/or ECM. | |
| Valve and/or valve guides worn or imperfect valve seat | Replace valves, rework valve seats or replace cylinder head if necessary. | |
| Inadequate fuel supply | Check fuel level in tank, add if necessary. Check/replace fuel filter, fuel supply lines, fuel pump and fuel injectors. | |
| Restricted air filter | Replace air filter. | |
| Restricted exhaust system | Replace restricted exhaust system components. | |
| Worn piston rings and/or cylinder bore | Replace piston rings and cylinders if necessary. | |
| Incorrect or contaminated engine oil | Change engine oil and refill with correct viscosity oil for ambient temperature. | |
| Engine knocks or pings | Fuel has octane rating that is too low | Use correct octane fuel. |
| Incorrect or worn spark plugs | Replace spark plugs. | |
| Intake air leak | Tighten intake flange, replace gasket or replace intake flange if necessary. | |
| Malfunctioning ignition unit or incorrect ignition timing | Check CKP and ECM, replace if necessary. | |
| Engine overheats | Low coolant level Cooling system leaking Air in cooling system | Refill coolant, pressure test cooling system. |
| Inoperative cooling fan motor | Replace cooling fan motor. | |
| Low engine oil | Fill engine oil to the proper level. | |
| Debris in radiator fins | Remove debris from radiator(s). | |
| Malfunctioning thermostat | Replace thermostat. | |
| Malfunctioning ignition unit or incorrect ignition timing | Check CKP and ECM, replace if necessary. | |
| Inoperative coolant pump or coolant pump drive | Replace coolant pump and/or coolant water pump drive. | |
| Inoperative oil pump or oil pump drive Damaged or improperly installed oil pump drive gear retaining ring Restricted oil circuit | Replace oil pump and/or oil pump drive components. Install oil pump drive gear retaining ring. Clean oil circuit. | |
| Leaking cylinder head gasket(s) | Replace cylinder head gasket(s). | |
| Intake air leak | Tighten intake flange, replace gasket or replace intake flange if necessary. | |
| Engine coolant temperature too low | Malfunctioning thermostat | Replace thermostat. |
Table 4-21. Troubleshooting: Engine Lubrication System
| CONDITION | CHECK | REMEDY |
| Blue smoke from exhaust or engine uses too much oil | Engine oil overfilled (oil in air cleaner assembly) | Adjust engine oil to proper level. |
| Leaking cylinder head gasket(s) | Replace cylinder head gasket(s). | |
| Valve stem seals leaking | Replace valve stem seals. | |
| Clutch hydraulic piston, secondary actuator cover piston bore or O-rings leaking | Replace piston, O-rings and/or secondary actuator cover if necessary. | |
| Engine oil contaminated with fuel, worn piston rings and/or cylinder bore(s) | Replace piston rings and/or cylinder(s). | |
| Engine oil contaminated with fuel, engine does not regularly reach normal operating temperature (short trips) | Operate vehicle for long distances in between short trips. | |
| Engine oil quantity increases | Engine oil contaminated with fuel, engine does not regularly reach normal operating temperature (short trips) | Operate vehicle for long distances in between short trips. |
| Engine oil contaminated with fuel, worn piston rings and/or cylinder bore(s) | Replace piston rings and/or cylinder(s). | |
| Low or no engine oil pressure - oil pressure indicator lamp illuminates | Engine oil level low | Fill oil to proper level. |
| Malfunctioning oil pressure switch | Replace oil pressure switch. | |
| Malfunctioning pressure retaining valve (bypass valve stuck in open position) | Check/replace pressure retaining valve. | |
Inoperative oil pump or oil pump drive Damaged or improperly installed oil pump drive gear retaining ring Restricted oil circuit | Replace oil pump and/or oil pump drive components Install oil pump drive gear retaining ring Clean oil circuit | |
| Leaking ignition cover gasket (oil pressure circuit leaking internally) | Replace ignition cover gasket and torque to specifications. | |
| Worn oil pump | Replace oil pump. | |
| Engine oil contaminated with fuel, engine does not regularly reach normal operating temperature (short trips) | Operate vehicle for long distances in between short trips. | |
| Engine oil contaminated with fuel, worn piston rings and/or cylinder bore(s) | Replace piston rings and/or cylinder(s). | |
| Restricted oil strainer | Clean/replace oil strainer. | |
| High engine oil pressure | Malfunctioning pressure retaining valve (bypass valve stuck in closed position) | Check/replace pressure retaining valve. |
| Restricted oil circuit | Clean oil passages. |