Wintertime Tips to Keep CNG Vehicles Running
Extreme wintertime weather may impact natural gas vehicle engine starting and performance. Low or decreased fuel pressure to the engine and cold intake air to the engine are the most common troubles when ambient temperatures are below freezing (32°F/0°C).
Although we cannot control the weather, we can take preventative measures to ensure proper CNG vehicle operation even during the harshest Arctic conditions.
This article focuses on compressed natural gas (CNG) fuel storage and delivery systems and how to prepare vehicles for reliable wintertime operation.
In extreme cold, several things can happen:
- Ice can form and thaw, creating condensation that can foul engine sensors
- The fuel pressure regulator diaphragm can freeze, causing improper regulation
- Fuel and fuel filters can become contaminated (high moisture content)
All of the above cause low fuel pressure delivery to the engine.
Low pressure troubles in the fuel system are caused by:
- System low on fuel (high pressure side: time to re-fuel the vehicle)
- Fuel leaks at the high or low-pressure side of the system
- Kinked or blocked fuel lines from debris or ice
- Plugged high or low pressure fuel filters
- Defective or worn fuel pressure regulator
- Regulator not being warmed with engine coolant
Engine components affected in extreme cold conditions include:
- Engine throttle plate can stick or not move freely
- Secondary fuel pressure regulator
- Intake manifold pressure/temperature sensor
- Charge-air cooler
- Throttle plate
- Exhaust gas recirculation (EGR) cooler
Ways to Increase CNG Vehicle Reliability in Cold Weather
- In extreme cold weather, O-rings in the fill receptacle may be frozen or the fill nozzle may not couple to the receptacle correctly, causing leaks when re-fueling. Try clearing the ice by inserting and removing the fill nozzle several times. If this does not work, replace the fill receptacle O-ring. If this does not solve the problem, contact the station operator.
Park vehicles in a warm garage or car port. But remember, an enclosed garage must be properly ventilated to prevent gas pockets near the ceiling and heating and lighting must not create a source of ignition.
Never park an LNG (liquefied natural gas) vehicle indoors, since fuel is vented in normal operation.
- Watch for frost or ice forming on fuel-carrying lines and components, especially the fuel pressure regulator.
- Frost or ice should never form on the CNG regulator: It is always warmed by engine coolant.
- Check for leaks or blocked coolant lines from the engine block to the regulator.
- Allow the engine to reach operating temperature before running the engine under load for best performance: The engine is warm when the vehicle heater is making warm air.
- Fuel quality and contaminants (water and compressor oil) may increase as weather changes. Check with your fuel supplier to make sure their station equipment is prepared for winter conditions.
- Make sure engine oil viscosity is optimized for winter weather and approved for natural gas service.
- Consider engine block and other heaters to keep things in the engine bay warm.
- Install a winter front to help retain heat under the hood.
Sidebar Article: Natural Gas Leak Testing in Extreme Cold
Leak testing in extreme cold weather is difficult because the leak detection solution can freeze, rendering a bubble or foam test impossible.
Use a leak detector solution such as Swagelok® “Real Cool Snoop,” rated to -54° F (-48° C) and keep the container in a hot water bath (bucket) to extend the “life” of liquid leak detectors.
Check for leaks as quickly as possible.
If fuel system parts are surrounded with ice, never chip it away with tools since this can cause damage. Always use a stream of water from a garden hose or bucket to melt the ice.
These simple tips will ensure your CNG vehicle will continue to start and run reliably, even under the harshest Polar Vortex conditions.