Doosan G430 LP Service Manual page 41

Problem
Carburetor Backfire
Poor High Speed
Performance/Lean
Condition
LP Engine G430 (3.0L)
Probable Cause
Incorrect full load air/fuel duty Verify full load air/fuel duty
cycle
Faulty vapor connection
between pressure regulator
and carburetor
Ignition malfunction
Incorrect ignition timing
setting
Engine mechanical
Clogged fuel filter
Plugged fuel line
Faulty vapor connection
between pressure regulator
and carburetor
Throttle butterfly not opening
Incorrect full load air/fuel duty Verify full load air/fuel duty cycle
cycle
Carburetor malfunction
Pressure regulator
malfunction
Incorrect ignition timing
setting
Air filter clogged
Check connection
No holes in hose
Clamps must be tight
Watch for kinked and/or pinched and/or
collapsed hose
Check ignition system, repair/replace
Check ignition timing
Measure initial timing
Measure centrifugal timing advance
See Troubleshooting section
Repair/replace as required
Close liquid fuel valve
Using caution, disconnect fuel line
Remove/replace filter element
Clean fuel filter housing
Open liquid fuel valve
Leak test
Remove obstruction from fuel line
Close liquid fuel valve
Using caution, disconnect fuel line
Clear obstruction with compressed air
Re-connect fuel line
Leak test
Check connection
No holes in hose
Clamps must be tight
Watch for kinked and/or pinched and/or
collapsed hose
Verify wide open throttle
Check carburetor
Remove air/gas valve assembly
Clean air/gas valve and carb throat
Check diaphragm for holes/damage
Check air/gas valve for wear/damage
Repair/replace as required
Test pressure regulator operation
Use test kit
Install primary pressure gauge
Install secondary pressure gauge
Crank engine and observe readings on
pressure gauges
Compare readings to specifications
If readings are out of spec repair/replace
pressure regulator
Check ignition timing
Measure initial timing
Measure centrifugal timing advance
Check air filter
Clean/replace as required
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Probable Solution
Troubleshooting