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Junior Member
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Discussion Starter · #1 ·
gotta 2.5TDi, 2006 and it appears to have a weird and unpredictable starting problem.

What usually happens it will start without any problems first thing in the mornings even from below - 4 deg C without a hitch.
But when its say been run for only about 15 mins, maybe popping into the newsagent, when i come to try and restart it when the engine is luke warm it just turns and turns and turns over on the starter motor, very brisky i may add, but fails to actually fire.

The battery is spot on as it will turn and turn over very lively but not fire
, ive tried the spare key incase a transponder issue key problem.

VAG Com'd by a mate and no fault codes stored.

My 'guess' is crankshaft sensor...............................???? but surely this wouold flag up a fault code

anyone else have a problem like this on these 5 cyl diesels?
 

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Mechanical Guru
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Not sure if this is right for PD engines but have read it somewhere that if one injector is faulty and shorting to ground non of the injectors will switch/fire. To check you have to pull off each injector connector in turn and when the faulty one is disconnected the rest will fire. Obviously you would need to check them at the temperature/time the engine refuses to start. This might be for common rail engines though.
 

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Hi Tregbert, is yours a 2.5 with engine code BAC and does it half fire up when starting, then cranks over fast as if the engine has no compression? Then when it starts it releases a cloud of black smoke? If so I suspect that the manifold shut off flap is sticking shut. This flap sits just before the inlet manifold and basicly shuts off the air supply to the engine when you switch off , it then re-opens . But if it doesen't re-open the problem I describes occurs. Let me if this is your problem
 

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Discussion Starter · #5 ·
Touareg tech said:
Hi Tregbert, is yours a 2.5 with engine code BAC and does it half fire up when starting, then cranks over fast as if the engine has no compression? Then when it starts it releases a cloud of black smoke? If so I suspect that the manifold shut off flap is sticking shut. This flap sits just before the inlet manifold and basicly shuts off the air supply to the engine when you switch off , it then re-opens . But if it doesen't re-open the problem I describes occurs. Let me if this is your problem
Hi Touareg tech, it is that exact model with those exact symptoms is the cure to clean around the flap???
 

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Well the problem was sure enough a clogged up flap in what is the EGR valve assembly, i simulated the actual problem today. So i removed the housing, firstly disconnecting the main air intake duct, unbolting the exhaust bypass gas pipe, disconnecting the vacuum hoses to the EGR valve and the vacuum operated valve mounted to the side of the housing. Lastly the 4, 5mm allen key bolts which mount it to the inlet manifold were removed, BINGO assembly removed, it needed a through clean as all gunked up with a mix of EGR gases, recirculated exhaust soot & alittle oil from the turbo pipes. After cleaning it was all reassembled and the flap operated fullly and correctly without sticking, job done.
So if anyone has occasional Starting issues with a 2.5TDi then look no further.
I will add that my touareg is a low mileage 32,000 mls from new, serviced every year, regardless of my low mileage and with the Correct VW longlife oil, and it still clogged up. Its often driven enthusiastically and only uses Shell Diesel, so question begs how can this be prevented??
 

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Hi Tregbert, I have only ever replaced the shut off flap to prevent customers returning to our workshop. But if it was my own vehicle i would removing it and try cleaning it out first, cheaper option but not guaranteed. let me what you do and if it works.
 

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I posted the last reply a bit late, I'm glad it fixed your problem . The clogging up happens on all the VW diesels , I have seen modifications on other models i.e golfs where they basicly put an oil catch tank in breather pipe to prevent the oil getting into the intake system. the mixing of the oil and the soot from the EGR causes the clogging up
 

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Mechanical Guru
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tregbert said:
so question begs how can this be prevented??
Well you could try disabling the egr by leaving the vac pipe off?? Commonly done on various Land Rovers without a problem but not sure about Vag cars.
 

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hi all! am i glad i found this thread. i seem to have the exact same problem, but i'll detail it anyway:

on colder days (i guess - it's winter now... and i haven't experienced it before) our 2006 r5 tdi (65,000mi) treg starts perfectly in the morning. then, if stopped and parked after just a brief roll downhill (ca. 5-10 minutes - engine's not getting up to temp - we live on hill, and post office and some shops are just below), it would not start again.

on successive tries it either:
- just keeps cranking over and over but the engine doesn't fire (never had the courage to wait out more then 10-15 secs of cranking - as it sound kind of scary -, so i killed the ignition for fear of - i don't know - doing damage, draining the battery),
- or it just cranks a beat and then does nothing.
but after a variable number of cycles (usually within the bounds of 10-15 minutes) of trying/retrying, waiting and trying again, it would fire up like normal and the day would go on...

i was beginning to loose faith in german engineering, and then i read this thread

and since i haven't dissected a "modern" engine before, and never a diesel (but there are no morals or lack of tools holding me back), i kindly ask if tregbert or touareg tech could provide a somewhat more in-depth (possibly illustrated) guide to accessing and cleaning the flap...

thank you very much in advance!
 

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Chairman
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Have you done a VAGcom check first to see if sny fault codes are thrown up?

Could be a temperature sensor issue.
 

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i tried to do some reading up on this.
checked ssp305
which exact flap are we talking about (refer to page 37)?
is it the
- Intake manifold flap change-over valve N239
- Exhaust gas recirculation cooler change-over valve N345
- Exhaust gas recirculation valve N18
??
the only repair manual i could find was in russian, any ideas where i could find one in english or german?
thanks
 

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Mechanical Guru
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i tried to do some reading up on this.
checked ssp305
which exact flap are we talking about (refer to page 37)?
is it the
- Intake manifold flap change-over valve N239
- Exhaust gas recirculation cooler change-over valve N345
- Exhaust gas recirculation valve N18
??
the only repair manual i could find was in russian, any ideas where i could find one in english or german?
thanks
Non of the above numbers, they are the solenoid valves.

The simplest way to find the valve itself is release the spring clip and remove the main air intake hose where it attaches to the EGR valve and you will see the flap inside no doubt covered in oily crap. For a quick fix wipe it out with a rag but for a proper clean it it's best removed then you can clean the whole EGR and manifold flap assembly. It's a messy job. a pair of gloves and mr muscle oven cleaner works ok.
 

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will try it the day after tomorrow... i think...
am i sure to recognize the "main air intake hose where it attaches to the EGR valve" once i remove the plastic cover? if not where should i look?
thanks
 

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done! success!!!

this morning it wouldn't start, exhibiting the usual symptoms.
(on a side note: just to add to the fun factor, my wife kept trying to start it while i got back home, and all the cranking/starting/stopping/whatnot eventually kicked the 3rd party alarm into engine lockdown, which would then not accept its override code... anyway, alarm tech came and reset it...)

so i checked "the flap" and sure enough it was clogged/stuck in a closed position, with more than 1mm (yep, checked with a toothpick) of cold soot/tar/oil/whatever covering the flap and the inside of that assembly.
did as much cleaning as i could without taking it all apart: used rags, oven cleaner fluid (that was a good tip), toothbrush and a bottle cleaning brush in various creative combos, and managed to get the flap and its surrounding sparkly clean (i wouldn't have guessed its nice shiny metal underneath when i started, but it is). the flap now behaves as should, defaulting to open position.

the car kicked into life and fired up flawlessly right on the first attempt afterwards!

so thanks for the help!
forums like this make the internet as useful as it is

cheers
 

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Chairman
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Well done.

Perhaps all diesel Tregs need an annual visit from the chimney sweep!
 

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last questions...
i decided i want to disassemble and clean the entire block.
- is there anything special about disconnecting the vacuum switch thing from the flap?
- if i do disconnect it, can i attach it again without special tools? (i DO NOT have a hand vacuum pump)
thanks
 
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