Diagnostic Information And Procedures; Ignition System Symptom Diagnosis; No Spark Or Poor Spark - Suzuki kq750 Service Manual

Ignition System Symptom Diagnosis

Condition
Spark plug not sparking
Engine stalls easily (No
spark)
Spark plug is wet or
quickly becomes fouled
with carbon
Spark plug quickly
becomes fouled with oil
or carbon
Spark plug electrodes
overheat or burn

No Spark or Poor Spark

Troubleshooting
NOTE
Check that the transfer is in neutral and the engine stop switch is in the "RUN" position. Check that the
fuse is not blown and the battery is fully-charged before diagnosing.
Step
1 Check the ignition system couplers for poor connections.
Is there connection in the ignition system couplers?
2 Measure the battery voltage between input lead wires (O/W
and B/W) at the ECM with the ignition switch in the "ON"
position.
Is the voltage OK?
3 Measure the ignition coil primary peak voltage. Refer to
"Ignition Coil and Plug Cap Inspection (Page 1H-3)".
NOTE
This inspection method is applicable only with
the multi-circuit tester and the peak volt adaptor.
Is the peak voltage OK?

Diagnostic Information and Procedures

Possible cause
Damaged spark plug.
Fouled spark plug.
Wet spark plug.
Defective ignition coil.
Defective CKP sensor.
Defective ECM.
Open-circuited wiring connections.
Open or short in high-tension cord.
Fouled spark plug.
Defective CKP sensor.
Defective ECM.
Excessively rich air/fuel mixture.
Excessively high idling speed.
Incorrect gasoline.
Dirty air cleaner element.
Incorrect spark plug.
Worn piston rings.
Worn piston.
Worn cylinder.
Excessive valve-stem to valve-guide
clearance.
Worn valve stem oil seals.
Incorrect spark plug.
Overheated engine.
Loose spark plug.
Excessively lean air/fuel mixture.
Action
Correction / Reference Item
Replace.
Clean or replace.
Clean and dry or replace.
Replace.
Replace.
Replace.
Repair or replace.
Replace.
Clean or replace.
Replace.
Replace.
Inspect FI system.
Inspect FI system.
Change.
Clean or replace.
Change to correct spark plug.
Replace.
Replace.
Rebore or replace.
Replace.
Replace.
Change to correct spark plug.
Tune-up.
Tighten.
Inspect FI system.
Yes
Go to step 2.
Go to Step 3.
Go to step 4.
Ignition System: 1H-2
B831G21804001
B831G21804002
No
Poor connection of
couplers.
• Faulty ignition switch.
• Faulty wire harness.
• Broken wire harness
or poor connection of
related circuit
couplers.
Go to step 5.