[locusjag]

Last month, my Jan 2018 manufactured TUV 300 T8 has had issues recently with the 'Check engine light' coming on due to a clogged intercooler and it had to be flushed. The turbo's hose had to be changed and the EGR valve had to be replaced. Everything seemed to be back to normal. I hadn't driven the car on the highway since then.

But on Saturday, on the highway, a couple of things happened -
1) The car was losing diesel fast, based on what I could see on the fuel level indicator on the dashboard. When we stopped for breakfast by the highway, I confirmed a fuel leak from the undercarriage. It turned out to be a crack on the main fuel hose that feeds into the fuel pump. Got that replaced by paying Rs.600 at a local mechanic's, near the Udumalaipet toll gate on NH 44.
2) The car's rear end, right upto the rear windshield and including the rear passenger footstep & rear hatch, was coated with black soot and ash. The rear passenger footstep (that leads into the 3rd row) had an inch of deposited greyish fly-ash. My rear window was dirty to the point where my IRVM was rendered useless.

#1 has been addressed and the hose's crack is attributed to age-related rubber hardening.

#2 is weighing heavily on my mind now. Was it because the ECU detected a lower fuel inlet pressure (due to the fuel input leak) and overcompensated by pulling in lots more fuel - and this led to a rich fuel-air mixture? This can cause excess soot in the exhaust.

#2 can also be due to a dying turbocharger, worst case (yikes!). It could be due to a clogged engine air filter (unlikely, as it was checked recently). It could be due to fuel injector issues. I just pray that the intercooler flushing/cleaning that was done last month had dislodged all the carbon from within and maybe the car was merely letting all that loose...

For now, I'll be looking at adding Liquimoly diesel additive to the fuel tank sometime soon.

[Bhupi_BHP]

Originally Posted by locusjag

Last month, my Jan 2018 manufactured TUV 300 T8 has had issues recently with the 'Check engine light' coming on due to a clogged intercooler and it had to be flushed. The turbo's hose had to be changed and the EGR valve had to be replaced. Everything seemed to be back to normal. I hadn't driven the car on the highway since then.

But on Saturday, on the highway, a couple of things happened -
1) The car was losing diesel fast, based on what I could see on the fuel level indicator on the dashboard. When we stopped for breakfast by the highway, I confirmed a fuel leak from the undercarriage. It turned out to be a crack on the main fuel hose that feeds into the fuel pump. Got that replaced by paying Rs.600 at a local mechanic's, near the Udumalaipet toll gate on NH 44.
2) The car's rear end, right upto the rear windshield and including the rear passenger footstep & rear hatch, was coated with black soot and ash. The rear passenger footstep (that leads into the 3rd row) had an inch of deposited greyish fly-ash. My rear window was dirty to the point where my IRVM was rendered useless.

#1 has been addressed and the hose's crack is attributed to age-related rubber hardening.

#2 is weighing heavily on my mind now. Was it because the ECU detected a lower fuel inlet pressure (due to the fuel input leak) and overcompensated by pulling in lots more fuel - and this led to a rich fuel-air mixture? This can cause excess soot in the exhaust.

#2 can also be due to a dying turbocharger, worst case (yikes!). It could be due to a clogged engine air filter (unlikely, as it was checked recently). It could be due to fuel injector issues. I just pray that the intercooler flushing/cleaning that was done last month had dislodged all the carbon from within and maybe the car was merely letting all that loose...

For now, I'll be looking at adding Liquimoly diesel additive to the fuel tank sometime soon.

Thank you for the update. Do post the future assessment as I myself own a March 2016 model and very eager to know about the cause.

[locusjag]

Originally Posted by Bhupi_BHP

Thank you for the update. Do post the future assessment as I myself own a March 2016 model and very eager to know about the cause.

Once I had gotten the cracked fuel line replaced by the side of the highway, I had gone on to my destination and then got back to Chennai via the highway. I hadn't seen any further soot nor ash deposits at the back of the car. Since then I've also driven within the city for around 60 Km in free flowing traffic (where I've hit speeds of 80 kmph); no soot/ash has been seen now either.

I think that this phenomenon was most probably due to the loss of fuel pressure, due to the cracked fuel line. The ECU must have sensed the lack of adequate inlet fuel pressure, overcompensated by pulling in a whole lot more fuel via the fuel pump, caused a richer than usual fuel-air ratio and ultimately caused a "rolling coal" effect. Gentlemen hailing from the southern US would have been thrilled if they knew that I was rolling coal here in South India.

It's either that - or there was loose soot shaken loose by the flushing of the intercooler (which I'd gotten done last month) and upon hitting highway speeds, I had shot all of it out of the exhaust. But this is unlikely because my FNG had taken the car onto 500 km of highway testing after the flushing and replacement of the turbo hose and EGR valve. My mechanic had wrung the car by hitting high RPMs deliberately - any loose carbon deposits should've been ejected back then itself.

[Bhupi_BHP]

Originally Posted by locusjag

Once I had gotten the cracked fuel line replaced by the side of the highway, I had gone on to my destination and then got back to Chennai via the highway. I hadn't seen any further soot nor ash deposits at the back of the car. Since then I've also driven within the city for around 60 Km in free flowing traffic (where I've hit speeds of 80 kmph); no soot/ash has been seen now either.

I think that this phenomenon was most probably due to the loss of fuel pressure, due to the cracked fuel line. The ECU must have sensed the lack of adequate inlet fuel pressure, overcompensated by pulling in a whole lot more fuel via the fuel pump, caused a richer than usual fuel-air ratio and ultimately caused a "rolling coal" effect. Gentlemen hailing from the southern US would have been thrilled if they knew that I was rolling coal here in South India.

It's either that - or there was loose soot shaken loose by the flushing of the intercooler (which I'd gotten done last month) and upon hitting highway speeds, I had shot all of it out of the exhaust. But this is unlikely because my FNG had taken the car onto 500 km of highway testing after the flushing and replacement of the turbo hose and EGR valve. My mechanic had wrung the car by hitting high RPMs deliberately - any loose carbon deposits should've been ejected back then itself.

Thanks for the useful update. I hope your estimate turns out to correct and the issue is resolved for good.