Section III. ORGANIZATIONAL TROUBLESHOOTING
ELECTRICAL TROUBLESHOOTING Ammeter:
Indicates constant "charge" condition with engine idling ... 4-17 Indicates no/low "charge" condition with engine idling ... 4-16 Engine:
Cranks, but will not start ... 4-16 Cranks slowly ... 4-15 Will not crank ... 4-15
4-10
Table 4-2. Mechanical Troubleshooting Procedures.
MALFUNCTION
TEST OR INSPECTION CORRECTIVE ACTION
ENGINE 1. WILL NOT START.
Check to see if fuel filter is clogged.
Replace fuel filter element (see paragraph 4-26).
2. DIFFICULT TO START/PERFORMS POORLY.
Step 1. Check to see if fuel is forming wax (winter operation).
Replace with winter-grade fuel (see paragraph 2-20).
Step 2. Check for erratic or insufficient fuel supply.
Bleed fuel system (see paragraph 4-21).
Step 3. Check for proper valve clearance.
Adjust valve clearance (see paragraph 4-13).
3. EXHAUST SMOKES EXCESSIVELY.
Check for proper valve clearance,
Adjust valve clearance (see paragraph 4-13).
4. TURNS OFF PREMATURELY.
Step 1. Check to see if engine idle speed is too low.
Adjust throttle control (see paragraph 4-25).
Step 2. Check for any broken or loose electrical connections.
Test and tighten loose electrical connections.
Step 3. Check for faulty compressor oil temperature or engine oil pressure shutdown switch.
Locate faulty switch and replace.
5. VIBRATES EXCESSIVELY.
Step 1. Check to see if engine idle speed is too low.
Adjust throttle control (see paragraph 4-25).
Step 2. Check for proper valve clearance.
Adjust valve clearance (see paragraph 4-13).
4-11
Table 4-2. Mechanical Troubleshooting Procedures (Con't).
MALFUNCTION
TEST OR INSPECTION CORRECTIVE ACTION
6. SURGES WHEN RUNNING.
Step 1. Check to see if regulating valve is restricted.
Replace regulating valve (see paragraph 4-94).
Step 2. Check for tension on engine speed control inner spring.
Adjust throttle control (see paragraph 4-25).
Step 3. Check to see if engine speed control springs are broken, Replace throttle control (see paragraph 4-25).
7. WILL NOT RUN AT CORRECT SPEED.
Step 1. Check to see if fuel filter is clogged.
Clean or change fuel filter element (see paragraph 4-26).
Step 2. Check to see if engine air cleaner filter is clogged.
Clean or change engine air cleaner filter (see paragraph 4-16).
Step 3. Check to see if pressure regulator is set too low.
Adjust throttle control (see paragraph 4-25).
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COMPRESSOR 1. BLOWDOWN VALVE OPERATES ERRATICALLY.
Step 1. Check for defective blowdown valve diaphragm.
Replace blowdown valve (see paragraph 4-95).
Step 2. Check for dirty blowdown valve.
Inspect and clean blowdown valve.
2. EXCESSIVE OIL CARRYOVER.
Step 1. Check for clogged oil scavenger line.
Remove and clean oil scavenger line (see paragraph 4-86).
Step 2. Check for oil carryover into discharge line.
Replace oil separator filter element (see paragraph 4-87).
Table 4-2. Mechanical Troubleshooting Procedures (Con't).
MALFUNCTION
TEST OR INSPECTION CORRECTIVE ACTION
Step 3. Check for defective minimum pressure and service valve.
Repair or replace minimum pressure and service valve (see paragraph 4-100).
Step 4. Check to see if unit was shut down improperly,
Instruct operator on correct shutdown procedure.
3. AIR DISCHARGE PRESSURE TOO LOW.
Step 1. Check to see if engine speed is too low.
Adjust throttle control (see paragraph 4-25).
Step 2. Check to see if air silencer is restricted or mesh is damaged or missing.
Clean or replace air silencer as necessary (see paragraph 4-94).
Step 3. Check blowdown valve for leaks.
Tighten or replace blowdown valve (see paragraph 4-95).
Step 4. Check regulating valve for leaks.
Tighten or replace regulating valve (see paragraph 4-94).
4. COMPRESSOR AIR UNSUITABLE FOR SANDBLASTING (EXCESSIVE OIL IN AIR OUTLET).
Step 1. Check for excessive oil in air lines.
Replace oil separator filter element (see paragraph 4-87).
Step 2. Check for clogged oil scavenger line.
Remove and clean oil scavenger line (see paragraph 4-86).
Step 3. Check for defective minimum pressure and service valve.
Repair minimum pressure and service valve (see paragraph 4-100).
5. OIL CONSUMPTION TOO HIGH.
Check for excessive oil carryover.
Refer to Malfunction 2, EXCESSIVE OIL CARRYOVER.
6. OIL BLOWS BACK INTO COMPRESSOR AIR CLEANER.
Check for damaged or defective unloader valve assembly.
Replace unloader valve assembly (see paragraph 4-90).
4-13
Table 4-2. Mechanical Troubleshooting Procedures (Con't).
MALFUNCTION
TEST OR INSPECTION CORRECTIVE ACTION
7. UNIT WILL NOT UNLOAD.
Step 1. Check for blocked regulating valve inlet.
Remove and clean regulating valve (see paragraph 4-94).
Step 2. Check regulating valve adjustment.
Adjust throttle control (see paragraph 4-25).
Step 3. Check for defective blowdown valve.
Replace blowdown valve (see paragraph 4-95).
8. SAFETY RELIEF VALVE RELIEVES.
Step 1. Check to see if safety valve pops off.
Replace oil separator filter element (see paragraph 4-87).
Step 2. Check to see if operating pressure is too high.
Adjust throttle control (see paragraph 4-25).
Replace unloader valve assembly (see paragraph 4-90).
Remove and clean regulating valve (see paragraph 4-94).
Replace safety relief valve (see paragraph 4-96).
9. START PRESSURE TOO HIGH.
Step 1. Check for blocked regulating valve inlet.
Remove and clean regulating valve (see paragraph 4-94).
Step 2. Check for defective blowdown valve.
Replace blowdown valve (see paragraph 4-95).
10. EXCESSIVE VIBRATION.
Step 1. Check for loose fan hub.
Tighten fan hub (see paragraph 4-92).
Step 2. Check for bent or broken fan blades, Replace fan (see paragraph 4-92).
Table 4-3. Electrical Troubleshooting Procedures.
MALFUNCTION
TEST OR INSPECTION CORRECTIVE ACTION
1. ENGINE WILL NOT CRANK.
NOTE
• Ensure that batteries are fully charged.
• Ensure that cables are good and correctly installed.
• Ensure that connectors are clean and secure on terminals.
Step 1. Check starter circuit fuse.
If bad, replace fuse (see paragraph 4-40).
If OK, go step 2.
NOTE
• When testing for voltage, negative lead from multimeter should be to ground (trailer frame).
• An assistant is required to push and hold the START button and SAFETY CIRCUIT BYPASS button.
Step 2. Push START button and test for voltage at switch terminals, Is voltage present?
If NO, replace start switch (see paragraph 4-46), then start engine to verify malfunction has been corrected.
If YES, go to step 2.
Step 3. Push START button and test for voltage at magnetic starter switch. Is voltage present?
If NO, repair or replace wire from start switch to magnetic starter switch, then start engine to verify malfunction has been corrected.
If YES, replace magnetic starter switch (see paragraph 4-61), then start engine to verify malfunction has been corrected.
Step 4. Push START button and test for voltage at starter solenoid. Is voltage present?
If NO, replace wire from start switch to starter solenoid, then start engine verify malfunction has been corrected.
If YES, replace starter (see paragraph 4-39), then start engine to verify malfunction has been corrected.
2. ENGINE CRANKS SLOWLY.
Step 1. Test voltage of batteries (see TM 9-6140-200-14).
If NOT OK, charge or replace storage batteries (see paragraph 4-57).
If OK, go to step 2.
4-15
Table 4-3. Electrical Troubleshooting Procedures (Con't).
MALFUNCTION
TEST OR INSPECTION CORRECTIVE ACTION
Step 2. Check battery cables for proper size, freedom of corrosion, and proper installation.
If NOT OK, repair or replace wiring harness (see paragraph 4-63).
If OK, go to step 3.
NOTE
If ambient temperature is below 32o F (0°C) check that engine oil and diesel fuel ratings are correct.
Step 3. Test current draw of starter motor,
If NOT OK, replace starter (see paragraph 4-39).
If OK, start engine to verify malfunction has been corrected.
3. ENGINE CRANKS, BUT WILL NOT START.
NOTE
• The engine must crank fast enough to obtain heat of combustion for ignition. If engine cranking speed is too slow, see Malfunction 2, ENGINE CRANKS SLOWLY.
• When testing for voltage, negative lead from multimeter should be to ground (trailer frame).
• Always replace wire with the same size (gage).
• An assistant is required to push and hold the START button and SAFETY CIRCUIT BYPASS button when testing voltage.
Step 1. Push START button and test for voltage at shutdown relay. Is voltage present?
If NO, test and replace wiring to shutdown relay. Start engine to verify malfunction has been corrected.
If YES, replace shutdown relay (see paragraph 4-62), Start engine to verify malfunction has been corrected.
Step 2. Push START button and test for voltage at fuel solenoid valve. Is voltage present?
If NO, test and replace wiring to fuel solenoid valve. Start engine to verify malfunction has been corrected.
If YES, replace fuel solenoid valve (see paragraph 4-59), Start engine to verify malfunction has been corrected.
4. AMMETER INDICATES NO/LOW "CHARGE" CONDITION WITH ENGINE IDLING.
Step 1. Check for loose, broken or slipping alternator belt.
If OK, go to step 2.
If NOT OK, adjust or replace alternator belt (see paragraph 4-37). Start engine to verify malfunction has been corrected.
Table 4-3. Electrical Troubleshooting Procedures (Con't).
MALFUNCTION
TEST OR INSPECTION CORRECTIVE ACTION
Step 2. Was charging system operating time limited?
If OK, go to step 3.
If NOT OK, charge batteries as necessary (see TM 9-6140-200-14). Start engine to verify malfunction has been corrected.
Step 3. Check for loose, dirty, or corroded terminals, leads, plugs, or connectors.
If OK, go to step 4.
If NOT OK, clean, repair, or replace terminals, leads, plugs, or connectors as required (see paragraph 4-63). Start engine and verify malfunction has been corrected.
Step 4. Check output condition of batteries (see TM 9-6140-200-14).
If OK, go to step 5.
If NOT OK, replace batteries (see paragraph 4-57). Start engine to verify malfunction has been corrected.
Step 5. With engine idling, check voltage at voltage regulator terminal.
If voltage is between 1.5-4 volts, replace alternator (see paragraph 4-36). Start engine and verify malfunction has been corrected.
If voltage is 24 volts, go to step 6.
Step 6. Perform voltage regulator test (open) (see paragraph 4-36).
If OK, start engine and verify malfunction has been corrected.
If NOT OK, replace voltage regulator (see paragraph 4-38). Start engine and verify malfunction has been corrected.
5. AMMETER INDICATES CONSTANT "CHARGE" CONDITION WITH ENGINE IDLING.
Step 1. Check for loose, dirty, or corroded regulator leads or terminals.
If OK, go to step 2.
If NOT OK, clean, repair, or replace as required (see paragraph 4-63). Start engine and verify malfunction has been corrected.
Step 2. Perform voltage regulator test (shorted) (see paragraph 4-36).
If OK, replace alternator (see paragraph 4-36). Start engine and verify malfunction has been corrected.
If NOT OK, replace voltage regulator (see paragraph 4-38). Start engine and verify mal-function has been corrected.
4-17/(4-18 Blank)