Hard Starting

SYMPTOM DESCRIPTION:
Engine cranks OK, but does not start immediately. Will eventually start and run, but may die shortly after.



SYSTEM OR COMPONENT TO CHECK

COMPUTER INPUTS/OUTPUTS

CHECK:

- CRANKSHAFT POSITION SENSOR: Damaged or defective crankshaft position sensor; missing, damaged, or severely worn flywheel teeth; poor connections or damaged wiring.
- CONTROL UNIT: Defective control unit. Poor connections, or damaged wiring to control unit.
- COOLANT TEMPERATURE SENSOR: Defective sensor, poor connections, wrong resistance value or damaged wiring.
IDLE VALVE: Stuck, restricted or partially closed idle stabilizer valve, poor connections, damaged wiring or defective control unit.



FUEL SYSTEM

CHECK:

- FUEL PUMP RELAY: Check for power at the fuel pump when ignition switch is in the start position and when the engine is running.
- FUEL SYSTEM RESIDUAL PRESSURE: fuel system should retain a minimum residual pressure when the engine is not running.
- COLD START VALVE: Clogged, stuck, poor connections or damaged wiring to control unit.
- FUEL QUALITY: Poor or contaminated fuel.
- FUEL FILTER AND LINES: Filter(s) plugged or restricted. Leaking, pinched, or restricted fuel supply lines.
- FUEL PRESSURE REGULATOR: Defective, system pressure too low.




IGNITION SYSTEM

CHECK:

- SPARK PLUGS: Wet with water or fuel, improperly gapped, heavy deposits, cracked insulators, or worn electrodes.
- SPARK PLUG WIRES: Damaged insulation, arcing to cylinder head or to other wires, secondary resistance too high.
- IGNITION DISTRIBUTOR, CAP, AND ROTOR: Check for cracks, arcing, moisture, rust deposits or high resistance through rotor.
- IGNITION TIMING: Check distributor basic adjustment. See IGNITION TIMING under ADJUSTMENT PROCEDURES



Also see Audi TSB #289002, #259005, #259109.