Troubleshooting; Engine - Subaru EX13 Service Manual

7. TROUBLESHOOTING

If the engine shows any sign of malfunction, the cause should be determined immediately
and appropriate countermeasures should be taken to prevent the problem from worsening .
This section describes certain known problems, their possible causes and appropriate
countermeasures . Note, however, that the list of problems presented here is not all . Generally
speaking, since there is the possibility of multiple causes for a single problem, please use your
experience and common sense when deciding on what action to take .

7-1 ENGINE

The following three conditions must be fulfilled for satisfactory engine start .
1 . The cylinder filled with a proper fuel-air mixture .
2 . Good compression in the cylinder .
3 . Good spark, properly timed, to ignite the mixture .
The engine cannot be started unless these three conditions are met . There are also other factors
which make engine start difficult, e .g ., a heavy load on the engine when it is about to start at low
speed, and a high back pressure due to a long exhaust pipe .
1 . Ignition system problems
2 . Fuel system problems
3 . Engine core components
problems
Problem and possible cause
1) Spark plug
• Improper spark plug gap
• Insulation defect
• Carbon deposits
2) Ignition coil
• Insulation defect or discontinuity
• Poor contact or broken wire
3) Improper air gap between ignition coil and flywheel
4) Bad wire harness
1) No fuel in fuel tank
2) Fuel hose, Return hose and Fuel pump pulse hose
clogged or pinched
3) Air in fuel lines
4) Poor quality gasoline or water in gasoline
5) Throttle body
• Overflow
• Clogged or damaged
• Throttle valve malfunction (does not close fully)
1) Insufficient tightening of cylinder head bolts
2) Wearing of piston, piston rings and/or cylinder
3) Improper contact of valve and seat
4) Valve sticking
5) Improper valve clearance
6) Leakage from intake manifold gasket
7) Leakage from carburetor gasket
8) Insufficient tightening of spark plug
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Remedy
Adjust the gap
Replace
Clean
Replace
Repair or replace
Adjust
Replace
Refill
Clean or replace
Check and retighten joints
Replace
Adjust
Overhaul
Check and adjust
Check and retighten
Repair or replace
Repair
Repair
Adjust
Retighten; replace gasket
Retighten; replace gasket
Retighten