Holley COMMANDER 950 - Manual (Page 73)

73
Appendix 4 GENERAL TROUBLESHOOTING
Double check ALL wiring connections and system voltages BEFORE replacing components. If you suspect an ECU or
component failure, check all other possible problems before replacing a component.
CONDITION POSSIBLE CAUSE REMEDY
1. Fuel Pump fails to
operate - Open or blown fuse
- Poor ground connection
- Faulty power relay
- Faulty fuel pump
- Faulty ECU
- Replace fuse
- Clean ground and tighten securely
- See Testing Relay section
- Check for voltage and ground at pump. If voltage
and ground are present, replace pump.
- Replace ECU
2. No fuel from
injectors - Open or blown fuse
- Poor ground connection
- Injector connection loose
- No fuel in tank
- Low fuel pressure
- High return fuel pressure
- Bad fuel pump
- No tach signal
- Faulty ECU
- Replace fuse
- Clean ground and tighten securely
- Inspect and clean connections, reconnect
- Add fuel to tank
- Install pressure gauges and adjust pressure.
- Kinked or restricted fuel line. Repair kinks and
remove obstructions from lines
- See Item 1 above
- Make sure proper ignition signal wire is used
- Replace ECU
3. Engine runs rich - High supply fuel pressure
- High return fuel pressure
- System not tuned properly
- MAP sensor hooked up improperly
- Faulty MAP sensor
- Oxygen sensor mounted incorrectly
- Faulty oxygen sensor
- Install pressure gauges and adjust pressure.
- Kinked or restricted fuel line. Repair kinks and
remove obstructions from lines
- See Tuning section
- Using vacuum gauge, ensure MAP sensor is hooked
up to full manifold vacuum
- See Testing MAP Sensor section
- See Oxygen Sensor installation in instructions
- Replace oxygen sensor
4. Engine runs lean - Low supply fuel pressure
- System not tuned properly
- Faulty MAP sensor
- Faulty oxygen sensor
- Incorrect system sizing - Install pressure gauges and adjust pressure.
- See Tuning section
- See Testing MAP Sensor section
- Replace oxygen sensor
- See Choosing the Right System
5. Hard starting (cold) - Faulty coolant temperature sensor
- Faulty air charge temp sensor
- Faulty IAC motor
- Fuel pump not flowing fuel - See Testing Coolant Temperature Sensor section
- See Testing Air Charge Temperature Sensor
- See Testing IAC section
- See Item 1 above
6. Hard starting (warm) - Engine flooding
- Faulty coolant temperature sensor
- Faulty air charge temp sensor
- Fuel pump not flowing fuel
- Use “Clear Flood” mode. Inspect injectors after
shutting off engine for injector leakage. Replace
leaking injectors.
- See Testing Coolant Temperature Sensor
- See Testing Air Charge Temperature Sensor
- See Item 1 above
7. Poor performance - MAP sensor hooked up improperly
- Faulty MAP sensor
- Faulty coolant temperature sensor
- Using vacuum gauge, ensure MAP sensor is hooked
up to full manifold vacuum
- See Testing MAP Sensor section
- See Testing Coolant Temperature Sensor section
8. High idle speed - Idle speed not adjusted correctly
- Binding or sticking throttle linkage
- Faulty IAC motor
- Faulty ECU - Set idle speed.
- Find cause of binding or sticking and correct.
- See Testing IAC section
- Replace ECU
9. Low idle speed - Idle speed not adjusted correctly
- Faulty IAC motor
- Faulty ECU - Set idle speed.
- See Testing IAC section
- Replace ECU
10. Surging idle - Engine running rich
- Engine running lean
- Idle fuel or timing not tuned correctly
- Throttle plates not adjusting - See Item 3 above
- See Item 4 above.
- See Tuning section
- Adjust throttle plates