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Running out of fuel not always simple…
On diesel systems, the empty fuel lines will probably need to be primed before restarting - there is a built-in hand pump for this near the fuel filter.
We all know that running out of fuel is something to be strenuously avoided, but I’m told that this applies even more to diesel than petrol. If this is true, then why?Pip
There is a difference, but it is not a big deal. When a starved petrol engine is refuelled, it will restart quite normally; perhaps a slightly longer engine crank first time while the fuel gets from the tank to the engine.
In diesel systems, the empty fuel lines probably have to be primed before a restart – there is a built-in hand-pump for that near the fuel filter. You press it repeatedly with the heel of your hand until it “hardens”.
Also, fuel pumps for diesel and petrol engines are not quite the same. Diesel (known in some markets as gasoil) is a lubricant; petrol is not.
So pumps for petrol have lubrication systems independent of the fuel itself and running out of fuel does not stop that. Some diesel pumps rely on the oily fuel to reduce friction between their moving parts, and running out of diesel will momentarily starve the pump of lubrication.
Some diesel pump designs have been changed since the introduction of low sulphur diesel, because sulphur was a significant element of the fuel’s lubricity.
Bear in mind that the engine does not stop as soon as the fuel tank is empty. It will keep running with the fuel already in the pipeline to the engine…and the fuel pump in the tank will keep running (without fuel) while it does so.
Irrespective of those factors, running a car with very little fuel in the tank is not recommended for several reasons: running out (if the gauge is faulty, or the next station is out of stock) the air: fuel mixture in a nearly empty tank is more explosive than a nearly full one; in a nearly empty tank dirt and detritus stirred at the bottom is more concentrated and could be sucked up and clog filters.