Fuel System Troubleshooting - Hard starting or no-start, ping on acceleration and more

General Automotive Repair

The general trouble shooting information lists common vehicle symptons with possible solutions and is not for any particular vehicle make and model. For repair info specifically for your make and model please view the main directory.

Engine Won't Start (Cranks Normally)

• Cold start valve inoperative: Test valve and circuit
• Poor connection vacuum or wiring
• Check vacuum and electrical connections: Contaminated fuel Test fuel for water or alcohol
• Defective fuel pump relay or circuit: Test relay and wiring
• Battery too low: Charge and test battery
• Low fuel pressure: Test pressure regulator and fuel pump, check for restricted linesand filters
• No distributor reference pulses: Repair ignition system as necessary
• Open coolant temperature sensor circuit: Test sensor and wiring
• Shorted W.O.T. switch in T.P.S.: Disconnect W.O.T. switch, engine should start
• Defective ECM: Replace ECM
• Fuel tank residual pressure valve eaks: Test for fuel pressure drop after shut down

Hard Starting

• Disconnected hot air tube to air cleaner: Reconnect tube and test control valve
• Defective Idle Air Control (IAC) valve: Test valve operation and circuit
• Shorted, open or misadjusted T.P.S.: Test and adjust or replace T.P.S.
• EGR valve open: Test EGR valve and control circuit
• Emissions Poor Oxygen sensor signal: Test for shorted or circuit
• Incorrect mixture from PCV system: Test PCV for flow, check sealing of oil filter cap

Poor High Speed Operation

• Low fuel pump volume: Faulty pump or restricted fuel lines or filters
• Poor MAP sensor signal: Test MAP sensor, vacuum hose and wiring
• Poor Oxygen sensor signal: Test for shorted or open sensor or circuit
• Open coolant temperature sensor circuit: Test sensor and wiring
• Faulty ignition operation: Check wires for cracks or poor con- nections, test secondary voltage with oscilloscope
• Contaminated fuel: Test fuel for water or alcohol
• Intermittent ECM ground: Test ECM ground connection for resistance
• Restricted air cleaner: Replace air cleaner
• Restricted exhaust system: Test for exhaust manifold back pressure
• Poor MAF sensor signal: Check leakage between sensor and manifold
• Poor VSS signal: If tester for ALCL hook-up is available check that VSS reading matches speedometer

Ping or Knock on Acceleration

• Poor Knock sensor signal: Test for shorted or open sensor or circuit
• Poor Baro sensor signal: Test for shorted or open sensor or circuit
• Improper ignition timing
• Check for engine overheating problems: Low coolant, loose belts or electric cooling fan inoperative

General Automotive Repair

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