Transfer fuel pump does not start in auto mode. Most common problem

Today, the transfer fuel pump does not start in auto mode, while it works normally in manual mode (the “Auto / Manual” button on the pump control panel).

In this article, we will analyze the most common cause of automatic pumps that work with the help of timers and floats.

Сircuit diagram of the transfer fuel pump

When looking at the diagram, it can be seen that four floats are involved in it to start and stop the pump. Two of them belong to one tank (HFO SETT. TANK), and the other two belong to another (HFO LS SETT. TANK). We are interested in the last heavy low sulfur fuel tank. It is when using this tank that the pump does not start in automatic mode.

Choosing a tank (floats) for pump operation

The most common reason why the pump in auto mode may not start in this case is a malfunction of the starting float. It should be activated by a low fuel level in the tank and at the same time give a command to start the pump.

Float switch on the tank

We find this float and first of all check the contact group inside it for close (or open, depending on the operation of the circuit). If everything works, then you need to remove it and check the inside of the float. Before removing it from the tank, you must make sure that there is no fuel in the tank (or if it is, then at least significantly below the level of our float).

Dirty float

The photo above shows that the float is very dirty and because of this dirt does not work. It moves depending on the fuel level in the tank, but the dirt clogged the magnetic contact part so that the contact does not close.

Float cleaning

After cleaning the float, we check the operation of the circuit. The problem is fixed, the pump works in auto mode. Additionally, it is importent to check the upper float, on which the pump stops.

Float

It happens that the float breaks or it breaks away from its stem (this is especially often observed in water systems). Also, additional timers fail, which are set for automatic operation of pumps not only in terms of levels, but also in time.

By the way, this circuit also uses a timer, but it was already installed separately in order to have additional protection against fuel overflow.