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Page 58
TROUBLESHOOTING
ENGINE SYMPTOM DIAGNOSIS
V-MAC III Diagnostics
When operating in cold weather, fuel waxing can
cause many of the problems described below.
Also, water in the fuel can damage unit pumps
and nozzles. Be sure to check for water in the fuel
and/or fuel congealing before proceeding to
troubleshoot a problem.
Also, refer to the V-MAC III service manual,
8-211, for applicable blink code information.
ENGINE WILL NOT CRANK
ENGINE CRANKS — WILL NOT START
Possible Cause
Correction
1. Batteries have low output.
1. Check the batteries. Charge or replace as required.
2. Loose or corroded battery or ground
connections.
2. Clean and tighten battery and ground connections.
3. Broken or corroded wires.
3. Check voltage at the following connections:
— Switch to starter
— Battery to starter
Replace as required.
4. Faulty starter or starter solenoid.
4. Check operation of starter and solenoid. Repair as required.
5. Faulty key switch.
5. Replace key switch.
6. Internal seizure.
6. Bar the engine over one complete revolution. If the engine cannot
be turned, internal damage is indicated. Disassemble engine and
repair as required.
Possible Cause
Correction
1. Slow cranking speed.
1. Check corrections listed in preceding chart, ENGINE WILL NOT
CRANK.
2. Code(s) present.
2. Correct cause of code(s). Refer to ENGINE MISFIRES —
CODE(S) PRESENT chart.
3. No fuel to engine.
3. Check for fuel in the fuel tank. Check for plugged fuel tank
connections, restricted or kinked fuel suction lines, fuel transfer
pump failure or clogged fuel filters.
4. Defective fuel transfer pump.
4. Check transfer pump for minimum output pressure. Change fuel
filters if low. Look for air leaks and recheck pressure. If still below
minimum, replace transfer pump.
5. Poor quality fuel, or water in fuel.
5. Drain fuel from tank. Replace fuel filters and fill fuel tank with
MACK-specified diesel fuel.
6. Incorrect engine oil viscosity.
6. Drain oil. Replace oil filters and fill crankcase with recommended
grade oil.
7. Low compression.
7. Check cylinder compression. If low, refer to LOW
COMPRESSION chart.
8. Faulty EUP fuel-return check valve.
8. Check for free poppet movement.
9. Faulty electrical connections.
9. Check electrical connections at ECU, engine position and engine-
speed sensor connections.
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