What would cause metal swarf to contaminate the whole fuel system of a car?

3 Lions · February 20, 2018

Hi,

So I'm on work experience in a service centre at a local dealership. Today (actually started the job yesterday) me and another young guy who I'm supervised by got this job where the car (in this case a 2017 Kia Sportage Diesel) was in for a fuel fault. Obviously modern diesels use a system called a common rail ignition system (Kia calls it CRDI) so we had to do a low and high pressure leak back test using a complicated kit supplied by Kia. After about 3 hours of setting up the test gear (it was really complicated) we were ready to do the test, we cranked over the engine a few times and found if I remember injectors 1,3 & 4 to be injecting correctly but 2 was really weak with small drips and pulsing while cranking. We came to the conclusion that the high pressure pump was damaged due to the metal swarf in the system and not providing the correct pressure for that certain injector, the fault was identified a week before I was actually there so that's how we know there is metal in the system but I think Kia requested to do the test anyway for warranty purposes. Basically the whole fuel system is toast with only a few fuels lines and tank salvageable (those can be cleaned out) the rest will all need replacing but what's confusing me is how did metal make it's way into the system, does anyone have any possible answers?

Thanks

bimmerman · February 20, 2018

VW had a similar issue in their 2009 era TDI engines, in the US at least. The high pressure fuel pump would fail, sending metal shards everywhere in the system, contaminating everything.

Some cars have a returnless fuel system where only parts downstream of the failed component get contaminated and need replaced, while others are return system where excess fuel is returned to the fuel tank from the fuel rail-- this is the kind of system that will contaminate everything if one component fails catastrophically. Ideally the fuel filter should catch any debris, but if the filter is upstream of the HPFP then it won't do much good. My understanding is the common systems feature a regular in-tank fuel pump that then feeds the HPFP closer to the engine, with the fuel filter in between.

BMW had an issue with the HPFP on their N54 turbo 6 cylinder engines, but I believe that was a returnless fuel system and that the pump failed without contaminating the fuel system.