Engine Starts, Then Dies

ENGINE STARTS, THEN DIES

Description
The engine will initially start, but soon after returning the ignition switch to "RUN", the engine dies.

Explanation
Basic elements of engine operation, such as ignition, fuel, and timing, are controlled differently depending upon the position of the ignition switch. The cause of this symptom is often a component which affects engine operation only when the ignition switch is in the "RUN" position.

When the ignition switch is in the "START" position, additional fuel and timing advance are added to ease in starting. Basic problems such as a lean Air/Fuel Mixture or incorrect Ignition Timing may become a factor once the ignition switch is returned to the "RUN" position.

Possible Causes
- Loss of Fuel
- Loss of Spark
- Retarded Ignition Timing
- Incorrect Air/Fuel Mixture
- Idle Speed Control

Loss of Fuel
Upon returning the ignition switch to "RUN", the Fuel Pump Relay may fail to remain energized. This problem may be caused by the following:
- Defective Fuel Pump Relay.
- Defective Wiring between the Fuel Pump Relay and the Ignition Switch or Powertrain Control Module.

Testing
- Install a Fuel Pressure gauge, and observe fuel pressure while starting. If the Fuel Pressure initially rises and then falls as the engine dies, check the Fuel Pump Relay for proper operation. Fuel Pump
- With the wheels blocked and the transmission in "PARK" (on neutral for manual transmissions), have someone listen near the fuel tank for the fuel pump to energize while starting. If the fuel pump initially runs for 3-5 seconds but then shuts off, check the Fuel Pump Relay for proper operation.

Loss of Spark
Upon returning the ignition switch to "RUN", the ignition system shuts off and the engine dies. This problem is often caused by an internal failure of the ignition switch but may also be caused by defective wiring between the Ignition Switch and the Ignition Module.

Testing
- Install an Ignition Timing Light (if possible with the pick-up lead attached to coil ignition cable, rather than # 1 cylinder) and point the light in a direction such that you may observe it while starting the vehicle.
- Start the vehicle and observe the timing light. If the dying problem is being caused by a Loss of Spark, the timing light will immediately stop flashing when the Ignition Switch is returned to the "RUN" position.
- Trace out and verify electrical power from the Ignition Switch to the Ignition Module. Ignition Switch

Retarded Ignition Timing
The engine will be difficult to start and the exhaust will have a distinctive dull and low sound. Once started the engine may not remain running.

Testing
- Observe the distributor and visually check for an abnormal adjustment. The distributor should be near the "middle" of its adjustment range. Ignition cables should not be pulled tight due to excessive distributor rotation.
- Remove #1 spark plug and bring the cylinder to Top Dead Center (TDC). The Timing Marks and Indicator should be very near the 0° TDC.
- If the Ignition Timing appears to be significantly out of range, check the Distributor for proper installation.

Lean Air/Fuel Mixture
The engine may be difficult to start, especially when cold. Once started the engine will run very rough and then die. When the engine is started additional fuel is added to ease in starting, but once the engine starts the additional fuel is removed and the Air/Fuel Mixture is too lean to sustain combustion. This problem is often caused by vacuum leaks but problems with the fuel control system or Fuel Pressure may also be at fault.

Testing
- Visually inspect all vacuum lines, intake hoses, and brake booster hose for evidence of leakage or wear. Diagrams
- Inspect the PCV valve and verify its operation. A PCV valve which is stuck open may act as a vacuum leak and cause a lean Air/Fuel Mixture. Positive Crankcase Ventilation
- Using a propane enrichment tool, enrich the mixture with a small amount of propane after the vehicle initially starts. If the engines continues to run and the idle speed increases, the Air/Fuel Mixture is too Lean.

WARNING: Propane enrichment is highly flammable and should only be attempted by experienced professional mechanics.

- If no vacuum leaks are found, check for low Fuel Pressure or problems with fuel control system.

Idle Speed Control
Improperly adjusted or defective Idle Speed Control may cause the engine to die immediately after starting.

NOTE: You should always verify the ignition system and fuel control system are operating properly before repairing or adjusting the idle speed control system.

Testing
- Visually inspect all adjustments and verify that no tampering has occurred (idle screws adjusted all the way out or all the way in).
- Start the engine and attempt to maintain engine operation by opening the throttle. If the engine runs normally off of idle, but dies when the throttle is closed, check the Idle Speed for proper adjustment and operation.