MOST PEOPLE KNOW that allowing a diesel-powered vehicle to run completely out of fuel is unwise.

Most modern diesel engines have a computerised priming function that you can use if you run out of fuel (after refuelling, of course!) However, if your battery is healthy, you may not need it.

Modern diesel engines use a low-pressure electric fuel pump, usually located in the fuel tank. This delivers fuel to a high-pressure mechanical fuel pump (HPFP) driven directly from the engine.

If you run completely out of fuel, air gets into the lines and the pumps. Sometimes, this will necessitate bleeding the entire system – both expensive and inconvenient.

However, once you have refilled the tank and switched on the ignition, the electric pump will push fuel into the lines, usually at about 3 bar of pressure. This will compress the air in the line into a much smaller volume near the HPFP. The HPFP delivers fuel at much higher pressure than the electric pump, feeding the piezo electric injectors that then pump tiny amounts of fuel directly into the cylinders at thousands of psi.

Given enough turns of the starter motor, this will purge the air out of the fuel lines.

One thing you should remember is that diesel fuel is also used as both lubricant and coolant. Running the tank dry risks damaging the pumps. Priming usually opens the fuel return to the tank and allows all of the air in the lines to escape back into the tank. The HPFP will get some fuel immediately and the injectors within two or three cycles. This will reduce, but not necessarily eliminate, the possibility of damage.

But the best advice of all: don’t run out of diesel fuel.

Whilst every care has been taken in the preparation of this article, information contained is for guidance only. seniordriveraus recommends considering your own particular needs, and seeking professional guidance and advice before making any decision