Many cargo vehicles have two fuel tanks. This adds additional factors to consider in situations where you see a fuel drain on the Mapon platform.
Below you will find a description of the factors depending on the technology used to determine the fuel level in the tanks.
Mapon fuel sensors for two-tank fuel system
Many customers who are involved in logistics and own trucks prefer the installation of fuel sensors for fuel monitoring. The main reason for this is the ability to monitor the volume and changes in the fuel in both tanks, as the integrated systems, whose data is delivered to Mapon via CAN bus, only monitor the fuel in the main tank.
However, if you see a fuel drain in a two-tank system with having Mapon fuel sensors, before you consider an actual drain you should check the following possible technical issues in addition to the reasons mentioned above:
make sure, that the vehicle's main power switch was not turned off and the vehicle was sending data all the time before the drain record appeared;
🚨 If the main power switch is being switched off or the tracking device of the vehicle goes power off for some other reason, then all fuel changes during this power off period are not detected by fuel sensors. Therefore, all the fuel-ups or drains that appear once the tracking device starts sending data again can not be analyzed without knowing what was actually done to the vehicle.
check if the signal from the fuel sensor in one of the tanks is lost;
turn on points display and check that none of the tanks have a long absence of data from the fuel sensor;
check if there are any delays in the flow of fuel from one tank to the other that could skip some important fuel level changes;
make sure that both tanks are in use, because switching off one of the tanks may cause issues with fuel calculations.
🚨 Manufacturers of trucks with two-tank fuel systems strongly discourage shutting off the second tank. It is only allowed to shut off the tank temporarily, in case of malfunctions in the connection between the tanks or in case of malfunction of one of the tanks.
CAN bus fuel level data for two-tank fuel system
The main disadvantage of CAN fuel data in case of a two-tank fuel system is the absence of a factory built-in sensor in the additional tank.
This means that the on-board computer has information about fuel changes only in the main tank, although it can have information about the total volume of both tanks.
🚨 All the fuel-ups or drains that appear once the tracking device starts sending CAN bus data can not be analyzed without knowing what has been actually done to the vehicle while:
the ignition was turned off;
the main power switch was switched off;
the tracking device of the vehicle was in power off status for some other reason.
For example, if a drain is displayed once the vehicle starts driving after a long stop and you see that it has stopped right after refueling, it means that there were fuel level changes while the ignition was off. CAN bus data is not being received by Mapon when the ignition is turned off, and in the meantime fuel can flow from the main tank to the secondary tank or vice versa to balance the fuel level. However, it still does not exclude the chance that the fuel was actually drained.
