TM 10-3930-641-34-1
ENGINE TROUBLESHOOTING (CONT)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
3. ENGINE MISFIRES OR RUNS ROUGH
Step 1. See if fuel pressure is low.
a. Check fuel tank and add fuel if needed.
b. Check for leaks, crimps, or bends in fuel lines between fuel tank and fuel transfer pump.
c. Check fuel transfer pump. Fuel transfer pump discharge pressure should be 30 psi (205 kPa).
Repair/replace fuel transfer pump. (See page 3-58.)
Step 2. Check for air in system.
Find leak and correct it. (See TM 10-3930-641-20.)
NOTE
Air will generally get into system on suction side of fuel transfer pump.
Step 3. Look for leak, crimp, or break in fuel line between fuel injection pump and fuel injection valve.
Replace line.
Step 4. Test for defect in fuel injection nozzle or fuel injection pump.
Test procedure:
Run engine at rpm's that produce misfiring. Loosen the fuel line nut on injection pump one
cylinder at a time. The faulty cylinder will not change the way engine runs.
Repair/replace the fuel injection nozzle or fuel injection pump for that cylinder. (See page 3-29.)
Step 5. Check valve clearance. (See page 3-268.)
Adjust valve clearance. (See page 3-268.)
Step 6. Inspect for bent or broken push rod.
Replace push rod. (See page 3-264).
4. ENGINE WILL NOT TURN HIGHER THAN 1000 TO 1200 RPM'S
Step 1. Inspect governor control arm for a restriction to movement.
Remove restriction. (See page 3-95.)
Step 2. Check adjustment of governor control linkage.
Adjust linkage. (See TM 10-3930-641-20.)
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