Failed MOT

jonb · Post by **jonb** » Sun Nov 18, 2007 11:41 am

Yesterday our Bongo failed its MOT for the first time in three years because the tester said that there was about twice as much black smoke in the exhaust as there should have been. The tester who I know and trust, tried to pass it (running the engine until it was hot, clearing out excess fuel etc. ) but he couldn't get the reading down.

The air filter is new, performance (acceleration, speed & mpg) seems fine to me, jet cleaner is regularly used & all seems normal apart from excessive black smoke.

Any ideas really appreciated.

Thanks

Jon

maxheadroom · Post by **maxheadroom** » Sun Nov 18, 2007 11:46 am

jonb,
Try blanking off the EGR, plenty of threads on the forum

Ralph · Post by **Ralph** » Sun Nov 18, 2007 12:58 pm

Do the EGR thing then give it a good blast " Italian tune up" then
slacken the throttle cable so it wont reach full throttle and try again.

bigdaddycain · Post by **bigdaddycain** » Sun Nov 18, 2007 1:40 pm

Does your tester definitely know the bongo's age jon? 1995? As correctly stated above, a sticking E.G.R valve will produce excess smoke when the engine has warmed,its not worth repairing, as you will see more benefit from removing, or simply blanking the system.

When you say smoke test...did you mean through the gas analyser?

Bongoflyer · Post by **Bongoflyer** » Mon Nov 19, 2007 11:03 am

When you say smoke test...did you mean through the gas analyser?

Good time for me to clarify this point which I have seen mentioned on here many times.

We have two seperate machines, a petrol gas analyser and
a diesel smoke tester.

The diesel smoke tester simply passes your smoke through a laser which measures its density.

The petrol gas analyser tests for CO, HC, and lambda.

That said modern machines are often combined but still work the same.

bigdaddycain · Post by **bigdaddycain** » Mon Nov 19, 2007 12:41 pm

Aha!...I see...

I was under the assumption that the one machine tested for the same emission related items whether it be diesel or petrol.

I have a diesel bongo,and at the m.o.t (e.g.r. removed 30% veg oil mix) The tester ran the five rev test thing (with probe in exhaust)...then muttered that it cant be right...removed the probe, then cleaned it,then said he was re-booting the machine as the figures were wrong.

I assumed the worst,and that my bongo was gonna fail the test

It turned out that he had difficulty in accepting the emissions were so low for a 12 year old vehicle,and he was getting the kind of reading he's expect from a 2003 car with a cat.

He got similar figures consistantly,with a slightly cleaner reading after each rev.

He'd even suggested that the engine was new,until i pointed out that it was my third mot with the bongo (bought with 12 months already on her) and the fourth year i'd owned her,the engine is the original as far as i'm aware.

So to clear up,the bongo would have been run through the DIESEL SMOKE TESTER and not the GAS ANALYSER?

Cheers for the clarification bongoflyer

Does the above tally with your experience of testing? (i'm assuming you are an mot tester)

dandywarhol · Post by **dandywarhol** » Mon Nov 19, 2007 1:40 pm

All diesels manufactured before 1979 only have a visual smoke test. The result of this is purely up to the tester's opinion.
Post '79 diesels go through a visual and smoke test, as bongoflyer says, it measures the density of the smoke in parts per million.

The max figure for a non turbo is 2.5 and 3.0 for a turbo diesel.
If the figure is below 1.5 on the first run then the vehicle passes. if not, up to 3 tests can be carried out and an average taken to meet the maximum allowed readings. If it is still too high, a further 3 tests can be carried out and an average of them will be used. (by that time all the soot/chip fat in the silencer will have well blasted out!

)

Kinda important to make sure your engine is capable of taking full throttle runs like this - especially the cam belt

If you think your van is borderline before the test, replace the fuel filter, adding some injector cleaner to the filter bowl and give it a sound thrashing! There's also nothing to stop you temporarily removing the air filter before the test either

Got mine tested yesterday - 0.5 on the first run - the tester beamed! "No bad fer an auld van!"

Bongoflyer · Post by **Bongoflyer** » Tue Nov 20, 2007 9:24 pm

Hi bigdaddy, yes I am a tester. Smoke tester is for diesels only.

mmmm, interesting post, as dandy said if your engine was so clean on the first run, (its called a fastpass) max 150ppm, then no need to continue on to the full six run test, why try to get a higher reading when you've got a pass. Maybe the chap was inexperienced.

The diesel smoke test is very far from rocket science and most vehicles pass it unlike the petrol test which is far more detailed and critical. I can usually tell if it'll pass the smoke test just by looking at the exhaust.

mikeonb4c · Post by **mikeonb4c** » Tue Nov 20, 2007 9:39 pm

Mango Bongo goes to Adrian in Bury for pre MOT check and MOT this Saturday. Wish her luck y'all - my hands are going clammy as I type

Bongoflyer · Post by **Bongoflyer** » Tue Nov 20, 2007 10:11 pm

good luck that you get a sensible tester Mike

Post by **Bob** » Tue Nov 20, 2007 10:39 pm

Fingers crossed for you and Mango, Mike.

Post by **Bob** » Tue Nov 20, 2007 10:42 pm

Bongoflyer wrote:good luck that you get a sensible tester Mike

Maybe we should try and get a block booking with Bongoflyer and have a get together in Essex. Doubtless we would get pulled for "Bongoing in a maner..."

bongolow · Post by **bongolow** » Wed Nov 21, 2007 12:12 am

Mango Bongo goes to Adrian in Bury for pre MOT check and MOT this Saturday. Wish her luck y'all - my hands are going clammy as I type

I think she's in capable hands there - I don't think Adrian will take it to the tester unless he's sure it's going to pass. I took mine for a service and MOT in September but he said it only needed an oil and filter change - he said it didn't even need the air filter changing (I know at least one garage that would have charged me for it anyway). Sound bloke. £140 for the service and MOT inc. the oil and filter.

mikeonb4c · Post by **mikeonb4c** » Wed Nov 21, 2007 12:33 am

Excellent - thats why - even though I try and do my own servicing - I reckoned the £70 for pre MOT check and MOT itself was a sensible investment. Oh and I've bought some diesle cleaner stuff to stick in it before I drive over to him and I'll give the engine a bit of a 'gunning' as they seem to say that is a good idea.

smartmonkey · Post by **smartmonkey** » Wed Nov 21, 2007 12:42 pm

Its very rare a diesel will fail on veggie oil. It normally drops the emissions right down to nothing - it may be a way of getting yours through. I would still do the EGR thing though.