If a diesel heater runs out of diesel, it will immediately stop operating due to fuel starvation. This isn't just a simple matter of refilling the tank; running dry introduces air into the fuel line, which then needs to be purged before the heater can successfully restart.
Immediate Effects of Running Out of Fuel
When a diesel heater exhausts its fuel supply, the combustion process can no longer be sustained.
- Shutdown: The heater's control unit detects the lack of combustion or fuel flow and initiates a shutdown sequence to prevent damage.
- Air Ingress: Crucially, the fuel pump continues to draw from an empty tank, pulling air into the fuel lines. This air becomes a major obstacle to restarting the heater.
- Fault Code: Most modern diesel heaters are equipped with diagnostic capabilities and will display a fault code indicating a fuel delivery issue or failed start attempt.
The Restarting Challenge: Purging Air from Fuel Lines
Simply refilling the diesel tank is not enough to get the heater working again. The air trapped in the fuel lines must be expelled for the fuel pump to effectively draw diesel to the combustion chamber. This process is often referred to as "priming" or "purging" the fuel system.
Steps and Considerations for Restarting:
- Refuel the Tank: Ensure the diesel tank is adequately refilled. It's often recommended to fill it completely to minimize the chances of air being trapped near the pickup.
- Attempt Multiple Start Cycles: The heater's fuel pump will try to draw fuel and expel the air during its start attempts.
- For a heater that is new or has run out of fuel, it can require up to 6-8 complete start cycles to fully purge the air from the fuel line and deliver fuel to the heater.
- Each start cycle typically takes about 6 minutes and includes two attempts by the heater to ignite.
- After these attempts, if it fails to start due to air in the line, the heater will likely display a fault code indicating a problem with ignition or fuel supply.
- Patience is Key: This process requires patience. Do not repeatedly attempt to start the heater in rapid succession without allowing it to complete its cycle and display a fault code, if applicable. Give it time to try and prime itself.
- Listen for the Pump: You might hear the fuel pump clicking more frequently or differently as it tries to draw fuel and overcome the air lock.
- Manual Priming (if necessary): In some cases, especially if the heater has a very long fuel line or is particularly stubborn, manual priming might be needed. This could involve using a hand pump if one is integrated into the fuel line, or loosening a fitting (with extreme caution and knowledge of your specific heater model) to allow air to escape. Always consult your heater's manual before attempting any manual priming methods.
Why Avoid Running Dry?
While not immediately damaging to the heater's core components, repeatedly running out of fuel can:
- Increase Wear: The fuel pump has to work harder and for longer durations to prime the system, potentially reducing its lifespan.
- Inconvenience: It can be frustrating to wait for the heater to prime, especially in cold conditions when warmth is needed urgently.
- Risk of Incomplete Priming: If not properly primed, the heater might run intermittently or inefficiently until all air is removed.
In summary, running out of diesel causes an immediate shutdown and introduces air into the fuel system, necessitating a patient priming process involving multiple start cycles to clear the lines and allow the heater to function again.
