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AIR-FUEL

Discussion in 'Diesel forum' started by vw754, Mar 23, 2007.

  1. vw754
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    vw754 vorsprung Durch Technik

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    My car is pulling air into the fuel system,i think from filter,anyway if a car pulls air in,would it use more fuel than normal

    A4 TDI B6 130BHP
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  2. Jason
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    Jason Member

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    Naaaaaa! Can't see any reason why or how it could use more fuel cos of a bit of air!!!

    Is it running ok,starting etc?????

    I've been running diesels for about 15 years now and they have all had the occasional or more air buble flowing through to the inj pump (notably last v6 tdi) that was well bad for it but have all ran well with out any problems as a result.
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  3. vw754
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    vw754 vorsprung Durch Technik

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    some weeks starts as soon as i turn the key,and some weeks takes 3-4 seconds to fire(as if theres no fuel) changed everything! new maf,fuel filter and seals etc no faults on diagnostics.

    just noticed on the T piece that fits on top of fuel filter,the pipe thats connected to that has some sort of sensor at the other end,any ideas what that is?
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  4. Jason
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    Jason Member

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    Not easy over t'internet!

    The only sensor that I could think of filter related would be "Water Drain".What are your return pipes like (injector to injector) they usually go quickly, depending on what fuel filter mounting you have the jubilee clips might be knackered letting air in and the fuel gravity feeds back to tank over night hence the 3/4 second start to pull it back through.

    Have you checked that the fuel sender pump in the tank is working? You can hear it!
    I once had an old Jetta that did the same thing turned out to be a blocked filter in the tank and as the injection pump couldn't get enough fuel through was sucking in air all over the place.
    Problem with air leaks is that they let air in but don't necessary let diesel out, so are a bitch to find!!

    Good luck

    Jason
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  5. vw754
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    vw754 vorsprung Durch Technik

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    pump works ok, if car is running (on idle) and i switch off and start immediatley,same thing takes 3-4 seconds to fire,so its sucking air in quick!

    Also this morning when driving i get (when i put my foot down) hesitation,a puff of black smoke,then it go's.

    Where and what checking should i do?
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  6. Jason
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    Jason Member

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    Bad starting from cold could be glow plugs,there is also a sensor that advances the timing for cold starting,this if knacked can cause cold and warm starting problems.Wunt worry too much about it though as it seems to be quite a common problem,my V6 tdi never started first click but it always started which is what matters.

    As for your hesitation, start with your EGR valve cleaning & blanking and clean your MAF (mass air flow sensor)
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  7. vw754
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    vw754 vorsprung Durch Technik

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    can you tell me where and what the sensor looks like that controls the timing?
    mine has starting problems,weather car is warm/hot/cold.
    im replace the non (fuel) return valve on wednesday,i think maybe fuel is running back to the tank,although fuel filter is full.
    This sensor that advances the timing,maybe something i could do with replacing,if the non return valve replacement fails. if you have any pics on this,it will be better,if not an idea on location is good enough.

    p.s egr valve was taken off car about 2 months ago and cleaned to a nice silver finish,as for the maf,replaced last week with a main dealer part.
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  8. Jason
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    Jason Member

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    Looks like that

    http://www.worldimpex.com/parts/genuine-part-water-temperature-sensor_118462.html

    And I think that you will find it on the inlet hose at the bottom of yeh radiator.

    Are you sure you have a good battery-diesels need em!

    As for your hesitation a smoke, check all yeh vacuem hoses,intercooler hose & remember if her in doors drives it it's gunna smoke afterwards.

    We had a 100tdi that after about a month on the school run I had to take it for a blast in 3rd at full revs for about a 2 miles to clear it out to get the dammed thing running again!!!!
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  9. vw754
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    vw754 vorsprung Durch Technik

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    OH THE TEMP SENSOR! REPLACED THAT 3 MONTH AGO-GENUINE AGAIN FROM AUDI!
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  10. vw754
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    vw754 vorsprung Durch Technik

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    fitted non return valve today....FAILED!!
    what next? is the temp sender i replaced a few months ago up the creek again?
    Also when cars on idle theres a strong fumey smell,smells very strong,so strong sometimes i have to close the window or i would choke (lol)
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  11. vw754
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    vw754 vorsprung Durch Technik

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    ive since found out cars sucking in air! Where andwhat do next?

    Ive done this so far,new filter,new filter seals,new non return valve,new T-piece (fitted on top of fuel filter) all audi parts.

    A4 tdi (b6) 2001 awx engine
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  12. Jason
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    Jason Member

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    VW754

    I have tried helping you but we seem to be getting no where!!

    What exactly is your major concern? air bubbles in your fuel line? 2 seconds to start or performance/running problems????
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  13. vw754
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    vw754 vorsprung Durch Technik

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    Heavy fuel consumption, (100 miles on 16 quid 91.9 pence per litre,17.41 litres!)

    Also 2-3 second before it fires in.

    2 problems above are main issue,where is it pulling air in from? ive checked pipes/filter and found nothing!

    been told its pulling in air,and because of the air its pulling in,the car will increase fuel to compensate the extra air,thus using more fuel.
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  14. golisago
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    golisago Member

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    Yes you can all change this T fitting on top of the fuel filter with the one a friend of mine sells in the states @ www.kermatdi.com look under widget or fuel filter widget , and will solve the bad valve problem plus air bubble problem in one...........if you fancy a group by i could sort it for you.

    I send this company vnt20/22 turbo's for there higher powered setups eg mk4 golf 90hp and pd 100hp respectively ............these can also be used on the asv pd 150hp and 130hp pd units to produce upto 240hp/250hp if the turbo is spec'd up right!!
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