After the recent timing belt change I had noticed a "harmonic" difference in the voice of my otherwise smooth sound of my 17 year old, 290,000Km trusty 2000 Ducato 2.8 Tdi Diesel. It seemed lower, more vibration and seemed to have a sweet spot just slightly higher on the RPM scale than before.

Well I just had my TUV, (MOT) performed in Germany and my exhaust emission numbers are up dramatically. On average throughout these prior years I have registered > 1.28, even last year before the belt change but yesterday I registered < 1.72!!!

Does anyone have experience with a timing belt change and exhaust particulate levels failure? It could be many things but this just seems to be such an abrupt change and the most obvious to begin this discussion with. The timing belt is the only recent variable in an almost unbelievably incredible engine's life's performance story.

Thanks in advance...

Quick Note:

I just noticed the exhaust side of the Motorhome and was surprised to see that the wheel hubcap behind the tailpipe fitting is completely black with soot! I had just checked the tyre pressure before returning from France only 1800Kms ago and would have noticed that black hubcap then but it wasn't in that condition then. There is also a lot of soot on the fender adjacent to the tail pipe.

This is all recent activity and a sudden change in the exhaust characteristics of an otherwise clean running engine. What could have happened so suddenly and why is it not effecting overall performance? I can still get up to speed normally, climb hills efficiently, etc. Help???

Quick Note:

I just noticed the exhaust side of the Motorhome and was surprised to see that the wheel hubcap behind the tailpipe fitting is completely black with soot! I had just checked the tyre pressure before returning from France only 1800Kms ago and would have noticed that black hubcap then but it wasn't in that condition then. There is also a lot of soot on the fender adjacent to the tail pipe.

This is all recent activity and a sudden change in the exhaust characteristics of an otherwise clean running engine. What could have happened so suddenly and why is it not effecting overall performance? I can still get up to speed normally, climb hills efficiently, etc. Help???

Most backyard belt changes are done by simply blocking the timing wheels, slackening the tensioner wheel, slipping off the old belt, slipping on the new, and adjusting the tensioner.

With the Ducato 1929cc diesel it's just so easy to get things a tooth out this way. You have to make sure the slack in the belt is to the tensioner side when refitting the belt, and this often means moving the crankshaft a bit to get the belt onto the crank wheel teeth, as you will have the cam-wheel and pump- wheel blocked.

Try advancing the injection one tooth, but turn it all over 2 turns with a long ring spanner before you try to start it, to make sure there's no piston to valve contact.

This has happened to me with my 1993 TD10 caravan.

hi
the pump timing could be out a few degrees.
its best to check the pump timing with a strobe timing
light and pulse sensor pick up on no.1 injection pipe.

Weekend coming and getting ready to get my head under the bonnet! Thanks for the tips!

One more founding query before I start camping out under the hood this weekend; I have noticed some talk around here and there of the EGR valve causing these test failures? Is this possibly the culprit? As my second post indicates, the sooting hadn't been an obvious issue until very recently, not even noticed until maybe the last 1500Km, just the roughness in the engine was noticeably obvious immediately after the new belt was installed.

[Found this post: https://www.fiatforum.com/ducato/328267-2-8-jtd-egr-valve.html]

To finish the story I have now passed the TUV in Germany. (MOT)

I couldn't find a EGR looking muffin anywhere on this engine so that was thrown out as a culprit. Next I thought I would try something obvious so I went and got a quality diesel treatment from Liquid/Moly and doubled the dose. I ran it through on the steep hills of the Mosel river and a few hundred kilometers on the Autobahn. Then booked another TUV exhaust test. My last test shown a out of tolerance reading of 1.74ppm and this test read .29, yes no typo .29ppm quite a surprise. The inspector said that there must have been a calibration issue at the other test station. Or, that the other inspector had entered the wrong vehicle data before the test. Oh well I am happy - the engine passed.

BTW. The engine treatment did loosen the injectors quite noticeably. That "Harmonic" is gone. So at the end of the day I believe that the roughness and boggy sound of the engine after the belt change may just have been a clogged injector that was fouled by the engine not starting when the belt originally "Jumped" before it's replacement. Who knows.

TIP. The TUV inspector told me to SLOWLY but evenly step on the accelerator to the high rev that the test requires. He said that "Stomping on the accelerator too aggressively to reach the test revs frequently leads to false test results." He also said, "A short rev between sequences will also clear away particulates that may foul the test results." Just something to think about next test if you are on the fringe of passing your next MOT.