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MOT Emission / smoke test failures. (Ducato 2010 18,500 miles)


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Further to my headlight problems (separate thread). The Ducato failed on emissions / smoke test.


The garage has put in a cleaning additive in the fuel and advised an “Italian Tune-up” before my next return. It was mutually anticipated the Mhome has been siting far too long between journeys and fill ups due to both winter and this Bl@@dyCovid thing !


The advice seems to echo other diesel users experiences from the web, similar problems have either been resolved, or not , by the above suggestions.


I am not sure if 18500 miles in ten years is a reason for emissions failure, but sitting around with old fuel might ?


However one item on the sheet did make me wonder what was going on regarding the test.


The sheet said no OBD port found. I have taken a look, but cannot find much about why the MOT station would need the OBD port.


Now I know where it is, Most of you know where it is. The MOT man probably knows where it is, but unwilling to take a screwdriver out to find it.


So I am not sure if it is wise to leave the facia open, for use of the port on the retest, or deny all knowledge that the port exists ?


Any thoughts ?



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No reason for him to look for the OBD port


With regard to the admissions test.


Most Motorhomes are driven around at 50 to 60 mph.


Ideally it needs some good quality fuel in ie. Shell.


We use this occasionally in our ford 16 seaters and the new Ford custom 9 seaters.


We drop it down a gear being as they are governed to 62 and take them for a run down the motorway.

Round trip 20 miles.


When using the Motorhome I’m very gentle on the throttle, but during a long run I’ll let it know who’s boss without overworking it.


Never had a problem since we’ve used these tactics.


During the 6 weekly checks on our buses we now add a fuel cleaner which is also supposed to help with regeneration of the exhaust.



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I took my old company car a Volvo to the local MOT station it was in for it's 2nd test (at 4 years)at way past 150K miles and it failed on the emissions. I rang the volvo dealer (where I had all the services done since new) and I was told that it was unheard of for such a car to fail. I took it in and it passed and it looked like the first MOT was carried out with the car not absolutely up to temperature when I arrived for the test it went straight in to the testing bay after a 40 mile drive?
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The ‘emissions’ element of the UK MOT test is covered in the following section of the MOT Inspection Manual.




Although the Manual contains NO reference to “OBD”, a GOOGLE-search shows that there is equipment that can be used for emissions testing by connecting to a vehicle’s OBD port. This 2018 discussion refers




There is clearly no mandatory requirement (yet) within the UK MOT test procedure to use OBD-connectable equipment for emissiions checking (or any other check), though a testing station might decide to use such equipment as a time-saving aid if they have the necessary kit.


(If you want to know exactly what "no OBD port found” is supposed to signify, ask the MOT testing station.)



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For 25 years I have made it a point to ALWAYS drive the van for about 10 miles at about 3000rpm to fully warm the engine/gearbox exhaust just before the MOT, check for leaks then drive it in for the test. They should warm it up properly, some do as you see them reving the engine for quite a while but others do not do it properly.
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The MOT test manual advises about temperature as follows


Vehicles first used after 1980 - vehicles must have an instrumented smoke test and it’s important to ensure the engine is at least 80°C or normal operating temperature if lower, before carrying out the test. You should check the engine temperature with an engine oil temperature probe or other approved device.


If due to the vehicle design, or where oil temperature measurement is impractical, the engine’s normal operating temperature may be checked by other means, such as the operation of the engine cooling fan. It is not normally sufficient to run the engine with the vehicle stationary to warm it up to temperature.

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Thanks for your replies.


Upon discussion with the garage and second MOT technician it would seem that first test the vehicle was not warm enough, although showing running temperature on the gauge the engine was not hot enough to test properly.


The failure notice gave no engine temperature reading, the pass gave 87 deg.


He no idea why OBD had been noted, original tester was not around to ask but he did comment that they have to test the vehicle as presented, and if its not up to heat there was little they could do about it with the time constraints. If its a small engine, it would probably be run for a short while to heat up. Running up a Ducato lump and heating system would be quite an ask !


So lesson learnt !


However, a 80 mile run with new Shell advanced fuel, a bottle of additive added by the garage and 30 mile run to get the engine hot before the second test has done the trick.


I usually run on Shell advanced, theory being that the Mhome sits around far more than it should do. I hang my head in shame, it would seem that I had not filled the tank up for nearly a year ! 600 miles since the last fill up mostly made up of 30 mile runs down to the beach since last September, so no wonder it was pulling the dregs ! Only excuse, if there is any, I just lost focus as the year went on due to a number of factors.


No chargemade headlight adjustments for the and repeat tests, so cannot complain.




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