Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Cold Start Valve
The cold start valve is used to provide additional fuel during the crank mode to improve cold engine starting. This circuit is important when engine coolant temperature is low. The main injectors are not pulsed long enough to provide adequate fuel needed to start a cold engine.
The circuit is activated only in the crank mode. The power is supplied directly from the starter solenoid and is protected by a fuse. The system is controlled by a thermal time switch. The thermal time switch provides a ground path for the valve during cranking when engine coolant temperature is below 95°F (35°C).
The thermal time switch is made of a bi-metallic material which is heat sensitive and is controlled by one of 2 factors. When coolant temperature is below 68°F (20°C), the switch is closed, feeding power to the cold start injector. However, cold start valve is still limited to an 8 second on time interval. Therefore this thermal time switch also contains a heating element. If the coolant temperature does not rise above 68°F (20°C) in less than or equal to the 8 second period, the heating element will have simultaneously heated the switch enough for it to open within the prescribed time period. In either situation the switch will in no way actuate the cold start injector for longer than an 8 second period.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.