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Diesel Engine
Running Out of Fuel

Unlike the earlier 90 Series Prado with switchable tanks, the Australian Specification 120 Series Prado will automatically switch to the sub tank when the main tank is empty. However, in many other regions around the world, the 120 Series Prado is delivered without a sub tank - and as aftermarket tanks are now becoming available, they are a popular option for those who desire a greater fuel capacity. Some of these aftermarket tanks employ a transfer pump or switch mechanism not unlike that found on the earlier 90 Series Prado.

The injector pump in the 120 Series Prado relies on a fresh supply of diesel fuel not only in order to run the engine, but to lubricate and cool the injector pump itself. The pump lifts a great deal of fuel from the tank and uses some to inject into the engine and the rest to lubricate and cool - returning this portion back to the tank.

When the fuel tank is empty, the pump starves for fuel and the engine will run roughly and eventually stop (usually with a puff of light blue smoke through engine oil ingestion and cold firing). This in itself may seem to be of little consequence however the additional wear and tear on the injector pump internal mechanisms is significant. In addition, there is a good likelihood that foreign particles that had previously settled in the bottom of the tank will be sucked up into the fuel filter.

Invariably this happens when you are travelling at speed in your Prado. Otherwise you will notice a lowering of the engine idle speed and momentary hesitation if not at speed. As soon as you notice this, you should stop the engine as soon as it is safe to do so. Switch tanks and repeatedly depress the pump primer (black disc on top of the fuel filter body adaptor) until resistance is felt. The fuel system will then be primed and ready to restart the engine.

Do not under any circumstances flick to the sub tank and continue to coast the Prado - turning the engine in order to lift fuel from the sub tank. This may take in excess of ten seconds - with the pump essentially running hot and with little or no lubrication. This is the point at which significant injector pump wear will occur.



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