2009 Mitsubishi Triton Pricing and Specs

What you’re probably hearing is the pump switching on to prime the engine’s fuel system so that it starts easily and promptly. Even though the engine isn’t running, when you switch the ignition on, systems like the fuel pump all come to life to get things ready to be started and driven. When the pump has generated enough fuel pressure and volume to start the engine, it can then switch off and only switch on again once the engine is running and a constant supply of fuel is required. This could be why it only runs for a few seconds when you first turn the ignition on.

This is pretty normal, but what isn’t is if the pump starts to make a new noise or the tone of its buzzing changes. At that point, what you might be hearing is wear or damage inside the pump.

This sounds like a case of a split fuel pick-up pipe in the fuel tank. When the tank is full, the split in the pick-up is covered by fuel, so the pump works normally at supplying the injectors with fuel. But when the level in the tank falls, the split is exposed and the fuel pump suddenly finds it’s much easier to suck air rather than fuel. And engines don’t run too well on just air.

This could be interpreted by a scan-tool as a fuel leak, so a check of the tank’s pick-up tube seems like a good place to start looking. Any actual fuel leak large enough to cause this problem would, presumably, be visible, but it’s worth a check of the fuel rail and return lines as well. Failing that, you could have a dud sensor that is telling the computer there’s a fuel shortage and sending the car into limp-home mode to protect the engine (which would also explain the loss of power). It would also be worth checking to see that the new Suction Control Valve (SCV) is working properly, even though it's brand new.

It sounds like it could be the fuel supply; check the fuel filter, fuel pressure, and the injectors. It’s a common-rail diesel engine and they are prone to injector wear.