Engine Starts, Then Dies

ENGINE START, THEN DIES

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

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

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 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.

Rich Air/Fuel Mixture
If the choke pull-off (unloader) fails to slightly open the choke after the engine starts, the Air/Fuel Mixture will be too rich for continued operation and the engine will stall.

If the float valve sticks open, fuel will overflow the carburetor bowl and flood the the engine just after start-up.

Testing
- Remove the air cleaner assembly and observe the carburetor while starting the engine. Carburetor
- If the engine is cold, the choke should remain fully shut until the engine starts. After the engine starts, verify the choke pull-off (unloader) slightly opens the choke plate.
- Verify that fuel is not spilling out of the bowl vents or venturis.

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. Fuel Delivery and Air Induction