Doosan D20S-5 Operation & Maintenance Manual page 136

Operation Section
HESITATION, SAG, STUMBLE
Checks
DEFINITION: The engine has a momentary lack of response when putting it under load. The condition can
occur at any engine speed. The condition may cause the engine to stall if it's severe enough.
Preliminary Checks
Fuel System
Checks
Ignition System
Checks
Additional Check
None
• Check the fuel pressure. Refer to LPG Fuel System Diagnosis.
• Check for low fuel pressure during a moderate or full throttle acceleration. If the
fuel pressure drops below specification, there is possibly a faulty low pressure
regulator or a restriction in the fuel system.
• Check the TMAP sensor response and accuracy.
• Check Shut-Off electrical connection.
• Check the mixer air valve for sticking or binding.
• Check the mixer assembly for proper installation and leakage. Check the EPR.
Note: LPG being a gaseous fuel requires higher secondary ignition system voltages
for the equivalent gasoline operating conditions. If a problem is reported on LPG and
not gasoline, do not discount the possibility of a LPG only ignition system failure and
test the system accordingly.
• Check for the proper ignition voltage output with J 26792 or the equivalent. Verify
that the spark plugs are the correct type and properly gapped.
• Check for faulty spark plug wires.
• Check for fouled spark plugs.
• Check for manifold vacuum or air induction system leaks.
• Check the alternator output voltage.
Action
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