Diesel Smoke Test

Gammy leg · Post by **Gammy leg** » 31 Jul 2009, 20:18

Chaps

Would the removal of the air filter improve the chances of passing the MOT smoke test ?( 1.9Td XUD ) Like what it used to for emissions tests for petrol engined cars.

Thanks

Xaccers · Post by **Xaccers** » 31 Jul 2009, 20:33

Having seen the damage caused by unfiltered debris getting into an engine, I'd not run without one.

If you haven't got time to sort out the main cause, I'd disable your EGR, fit a new air filter, fill the tank with new vegetable oil, and give it a heck of an italian tune up

Make sure the engine is nice and hot before the MoT

Gammy leg · Post by **Gammy leg** » 31 Jul 2009, 21:19

It gets a fluids & filter change + injector treatment before every MOT but it still struggles to pass the smoke test. It is only the perserverence of the friendly tester that normally gets it through. I'm taking it somewhere new this time and can't rely on the new chap being as amenable.

Back to the original question, would removing the air filter make any difference.

Thanks

citronut · Post by **citronut** » 31 Jul 2009, 21:28

can i ask were you arte taking it for the MOT, and were did you go before,

im in St Leonards on sea, and i have been useing Bridge Garage Sedlescombe (01424 870202) for around 30 years, they are very good and have lots of PERCY WHAT SIT,

also as Xac said give it a realy good mexican tune up on route to the MOT,

even if it means going the long way to the test station,

dont get there early or the engine will cool down whilst waitting for the probe to be shoved up its do dah

regards malcolm

Gammy leg · Post by **Gammy leg** » 31 Jul 2009, 21:49

Malcolm,

I used to take it to LMW next to the station at Westham ( BMW independant specialist), But there's b*gger all to do there while i'm waiting. I've sorted this one tomorrow via the web at justmots.eu and its just up the road in Bexhill town. Paid upfront at £39.00. Any experience of them??

Gammy

citronut · Post by **citronut** » 31 Jul 2009, 22:02

none as yet but i thought you dont pay untill you get a pass, we have one in st leonards somewere, they should be completely unbiased as they dont do any repaires,

if you find your self over this way in the week you are welcome to pop in at my workshop/hoval for a chat,

im also after guiney pigs for my LEXIA and dont charge much

regards malcolm

ps.
if you would like details on how to find my workshop i will send you a pm

Post by **Peter.N.** » 31 Jul 2009, 22:49

If it has a Bosch pump, its very easy to reduce the fueling.

falling-out-with-my-car · Post by **falling-out-with-my-car** » 01 Aug 2009, 10:16

Gammy Leg,

removing the air filter will allow small dust particules to enter the engine and could contaminate your oil, the injectors may still be dirty if your adding injector cleaner to the fuel tank.

firstly whats the engine oil like was it changed before the MOT. I know we are talking about a diesel here but on a petrol engine simply changing plugs, oil and air filter can make all the difference to an emmission test and has done frequently on one of mine.

Before every M.O.T I remove the top of my diesel fuel filter, remove the filter and drain off the diesel inside, replace the filter and in the middle there is a hole, pour diesel injector cleaner in its neat form into the midle of the filter until the filter housing is full.

bolt the lid back on and as said before go for an Italian tune up/run.
if you havent got any 60 or 70mph roads very close to home start the engine and give it a good rev, only dont hold the throttle down to long and definately dont switch off the engine until it returns to idle apparently you can damage the turbo if you turn the engine off at high revs.

I always drop my throttle cable back 2 notches before MOT's as well this stops the engine being reved to hard. you can always put the clip back up two notches after MOT. it makes hardly any difference at all to driving.

sometimes if you are only using your car for short runs it is necessary to do this twice, you will be suprized at the muck that comes out of the exaust. one 500ml bottle should be sufficent for nearly two goes.

it is very important to get the engine Hot before testing and on arrival at the testing station tell the tester that it has just been for a nice run so the engine is hot, this will save the tester a lot of time getting the engine up to temperature on idle.

I'm not to confident about putting neat veggie oil in my Xantia for a start it doesn't like it even though I have a Bosh fuel pump, which is something you check out before you put veggie oil in it otherwise you may damage your pump. it also gels in my fuel filter, others will contradict this but it does happen in my fuel filter, even with pure rapeseed oil.

I only use it in a 50/50 mix I find I get a better mpg that way and no gelling.

I usually find the injector cleaner in the filter housing gives very good results effectively you are running on neat cleaner n ot thinned down by what is in your tank. I use stp injector cleaner or wynns for diesels available at asda. I have never used green redex so I can't be sure on the reslts for redex I would imagine that the results might be similar for most diesel injector cleaners.

it should work ok.

regards Nigel.

Old-Guy · Post by **Old-Guy** » 01 Aug 2009, 11:20

There's a very easy and entirely harmless way to reduce the fuelling on an XUD TD: simply disconnect the boost pressure sense pipe. This is about 10mm OD and goes to the top of the injector pump from the big black plastic air pipe, which in turn comes from the turbo (down behind the engine) over the engine and down to the intercooler.

The car will feel a bit gutless to drive, but it may help it pass the stupid smoke test. I say stupid because the test bears no relation to emissions on the road (under load).

Of course this won't help if your problem is worn injectors.

citronut · Post by **citronut** » 01 Aug 2009, 11:27

on taking my own and customers cars to an MOT i just floor the pedel for a few seconds in second gear two to three times, this is usualy is enough to give them a good clear out, it varies how thick and black the cloud is behind the car,

i cant remeber the last diesel car i had fail on emmisions,

also a diesel component technician told me he dose not like the use of injector cleaners, as they are mostly abbrasive and damage the ijectors

regards malcolm

Old-Guy · Post by **Old-Guy** » 01 Aug 2009, 11:57

I don't believe any (reputable) brand of injector cleaner contains any abrasive (particles). What they all do contain is a fairly aggressive mixture of detergents and solvents. The solvents will reduce the essential lubrication properties of the fuel - especially if used in concentrations higher than recommended by the manufacturer. There's a very good reason why the prescribed concentration is so small!

Personally I think that a dose of neat cleaner in the fuel filter is a very BAD idea. The pump and injectors will be operating for many thousands of cycles with virtually no lubrication!

The precision moving parts in both fuel pump and injectors depend on proper lubrication (under very high loads) being provided by the fuel. When ultra-low sulphur fuels were first introduced in Europe (Scandinavia) there was a spate of injection system failures - particularly on big trucks - caused by the poor lubrication properties of the new fuels. According to rumour, Scania (and others) had to do warranty repairs on thousands of injection systems wrecked after only a few thousand kms on the new fuel. It's said the fuel companies eventually picked up the huge bills under threat of legal action.

Gammy leg · Post by **Gammy leg** » 01 Aug 2009, 19:06

Panic over, it passed. Time to come clean...... I did nothing apart from add some injector cleaner to the tank the night before. No oil change, no new filters, nowt.

As usual the guy had to run it through 2 test cycles before the readings fell below the maximum allowed but then it was fine. Sorted for another year.

Thanks for all the input chaps

Gammy

citronut · Post by **citronut** » 01 Aug 2009, 19:10

glad to hear your sorted

regards malcolm

falling-out-with-my-car · Post by **falling-out-with-my-car** » 02 Aug 2009, 13:50

good to hear your sorted Gammy,

emisions tests can be so fickle you can get a failure in the mornning and a pass in the afternoon having done nothing to the car.

Old guy, I appreciate your comments on lubrication but no-one is cutting off the supply of diesel before the filter and drainning diesel already between the filter and the injectors, I have done this cleanning via filling the filter for many years with my diesels and never had a problem with it, I suppose it could be down to which cleaner you use and who recommends what, I was advised to do this by a citroen mechanic, it has never failed in getting the car through its emmissions test it has always passed first attempt fast pass.

regards Nigel.

Post by **Paul-R** » 02 Aug 2009, 14:02

I always thought that diesel additives ADDED lubricity to the fuel anyway.