Onan MEP-003A - Page 36

TM5-6115-585-34
NAVFAC P -
8-262-12
TO
- 35C2-3-455-2
TM - 05684C - 34
Table 2-3 . Troubleshooting ( Cont )
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
13. METALLIC KNOCKING , CLICKING , OR POUNDING FROM CRANKCASE OR CYLINDER BLOCK .
Step 1. Check for worn or loose connecting rod bearings ( paragraph 7-10 ) .
Replace
bearings
if
necessary
.
Step 2. Check for loose piston and connecting rod assembly ( paragraph 7-10 ) .
Repair or replace assembly .
14.
LOW
ENGINE
COMPRESSION
.
NOTE
Normal cylinder pressure is between 350 and 450 psi depend
ing upon engine condition . Maintenance should be considered
if pressure is below 325 psi or if there is a 15 percent or
mor
difference between cylinders
.
Step 1. Check for loose cylinder head ( paragraph 7-9 ) .
Properly
tighten
head
.
Step 2. Check for leaky head gasket ( paragraph 7-9 ) .
Replace gasket .
Step
3.
Check
for
broken
valve
spring
(
paragraph 7-9
) .
Replace
broken
springs
.
Step 4. Check for sticking valves ( paragraph 7-9 ) .
See
sticking
valve
section
below
.
Step
5.
Check
for
leaking
valves
(
paragraph 7-9
) .
Clean and , if necessary , regrind valves and valve seats .
Step 6. Check for worn or sticking piston rings ( paragraph 7-10 ) .
Replace rings if necessary . Check condition of cylinder walls .
Step 7. Check for worn cylinder walls and pistons ( paragraphs 7-10 and 7-19 ) .
Refinish
cylinder
walls
.
Repair
or
replace
pistons
.
15. STICKING VALVES .
Step 1. Check for dirty , scored , or gummy valve stems or guides ( paragraph 7-9 ) .
Clean
stems
and
guides
. If
necessary ,
replace
guides
.
Step
2.
Check
for
weak
or
broken
springs
(
paragraph 7-9
) .
Replace springs .
2-9