Hi guys, i have a 2003 5.9 cummins diesel 1ton dually 4x4 with 255.000km, im leaking diesel, badly, from somewhere behind the fuel filter i think though, not sure! i cant figure it out!? lift pump? what could it be? thanks konrad

 

roughly 160.000 miles...

 

Have you changed the fuel filter recently? If so, could the gasket have been pinched?

 

Take the fuel filter lid off and check the gasket around the lip. Also check the cover for cracks, it's plastic and can break if over tightened.

 

Check the return line banjo bolt on the back side of filter houseing. Might want to check the water drain valve on the bottom of the filter houseing. Also take a look at the fuel line on the back of the filter houseing that comes from the lift pump.

 

My number 5 injector line on the rail started leaking about two years back. tightened it up and it was fine after that.

 

My 99 leaked from the heater wires that go into the filter

 

Check the #6 injector line coming from the common rail. It's a long run and unsupported and prone to cracking from vibrations. DO NOT stick your hand back there when the engine is running!! Can be deadly!! Use a piece of cardboard to check for leaks.

If it is the injector line order a new one and a support bracket used on the later models that mounts to the engine lift bolt.

MikeyB