TOHATSU BFT115A Service Manual page 96

TROUBLESHOOTING
ENGINE SOMETIMES MISFIRES OR TENDS TO STALL
1. Spark Plug Inspection
Remove and inspect the spark plugs.
Is the spark plug wet?
YES
NO
2. Spark Test
Perform the spark test with each ignition coil (page 8-4).
Is there normal spark?
YES
NO
3. Fuel Flow Inspection
Inspect the fuel flow (page 5-130).
Is the fuel flow within specification?
YES
NO
4. Pressure regulator inspection
Check the fuel pressure and record it (page 5-129).
Disconnect the pressure regulator control tube.
Check the fuel pressure.
Is the fuel pressure higher with the control tube disconnected?
YES
NO
5. Fuel injector inspection
Inspect the fuel injector (page 5-134).
Is the fuel injector normal?
YES
NO
6. IAC valve inspection
Replace the IAC valve with a new one and start the engine.
Does engine sometimes misfire or tend to stall?
YES
NO
4-6
– • Incorrect spark plug heat range
• Incorrect spark plug gap
• Restriction or blockage between the silencer case and cylinder head
• Improper vapor separator float height
– GO TO STEP 2.
– GO TO STEP 3.
– Perform ignition system troubleshooting (page 8-3).
– GO TO STEP 4.
– • Clogged, bent or damaged fuel tube
• Clogged fuel strainer (Low pressure side) (page 3-24)
• Clogged water separator (page 3-24)
• Faulty fuel pump (Low pressure side)
• Clogged vapor separator air vent tube or filter
• Faulty vapor separator (page 5-133)
• Clogged, bent or damaged fuel feed hose
• Clogged fuel strainer (High pressure side) (page 3-26)
• Faulty fuel pump (high pressure side)
– GO TO STEP 5.
– Faulty pressure regulator
– GO TO STEP 6.
– • Repair the open or short circuit fuel injector wire
• Faulty fuel injector
– Replace the ECM with a new one and recheck.
– Faulty original IAC valve