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What should fuel pressure at idle be???

Discussion in 'A3/S3 Forum (8L Chassis)' started by darren t, Feb 19, 2013.

  1. darren t
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    darren t Member

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    I have my boost gauge fitted on fuel pressure reg line I am going too change it but ive noticed a change in its idle vacume??? My gauge reads in bar and used too sit at 0.7 bar now it sits at 0.9 bar I have no leaks and getting bank 1 below threshold code I've erased done a run 2 junctions on motorway and checked blocks 031/032 0.8 in block 1 and block 2 1.6 the lambada before cat is new??? Genuine Audi??
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  2. Broken Byzan
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    Broken Byzan Photographic Moderator Staff Member Moderator

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    Translation please?
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  3. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Ooooooooooook.... so I understand this... you have connected your boost gauge to the fuel line???

    How?

    Anyway... fuel pressure on idle with a 3bar FPR will be just under 3bar as its on vacuum... typically 2,7ish bar... really don't think a boost gauge is setup for fuel pressure not to mention if you have hooked it up how I think you have its could be quite dangerous...

    Most fuel pressure gauges use electric senders as this is safe...

    The last bit of you r question makes little sense... please re-word... and include the actual fault codes...

    <tuffty/>
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  4. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    ok... having re-read it several times I think I understand what you are asking...

    You are asking what the pressure should be at the vacuum line of the FPR? on idle? this can vary depending on various conditions... aircon, lights etc... the ECU clearly thinks it needs to open the throttle plate less to have enough load to keep idle going... this can also vary dependant on outside temp and of course airleaks else where... mine sits at -0.7bar typically but can increase in vacuum...

    ...also.... I am guessing you are getting an adaption fault code? one thats taking too much fuel out? are you still running a 4bar FPR?

    1.6% is nothing in terms of adaption... long term fuel trims normally vary between +/-5% under normal conditions anyway

    <tuffty/>
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  5. darren t
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    darren t Member

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    cheeres for the reply tuffty I am booking in for a map Monday with bill but I've had more problems lol yes I have put my 3 bar fpr back in ages ago when advised my trims are adding fuel ie 0.8 and 1.6 and my vacume used too be 0.7 aswell it has since risen too 0.9 I have checked all connections and all seem ok??? I think my fuel pump could be going bad??ill try fuel filter and another fpr today yes I've teed into my vac line for fpr there is no leaks there!my fault codes came whenthe intercooler pipe poped off I had check DV code that was my pipe coming off then I got maf signal too high then it threw lamba bank 1 insufficient flow?
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  6. darren t
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    darren t Member

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    Am I right in thinking trims must have gone over +25/-25 too trigger the lamba code anyway?after the drive I did check readiness and all passed except catalysts and sensors??
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  7. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    Don't confuse the vacuum with fuel pressure.... vacuum varies as I said before and what the engine is doing in relation to the throttle flap dictates the vacuum you have at any given time...

    Signs of a bad pump is rising lambda compensation in block 001 under boost as its compensating for low fuel pressure by adding injector duty... this will eventually lead to long term fuel trims going +25% and throwing a fault code but typically this takes a while before it happens as under normal driving conditions (not driving like you stole it) a dying pump can normally keep up...

    Trouble is that due to your current setup and the fact the mapping is not right for it then this can also lead to the ECU adding fuel as the airflow is different... normally the ECU can compensate easily for this but when you mod the car to this level the fuelling needs to be recalibrated under boost... I don't know if you have changed the injectors too but if you have then this will be throwing a curve ball too as they will need dialling in to the map...

    I still think you are chasing issues that will most likely go away once mapped mate...

    Yes... ECU adaption limits are +/-25%

    <tuffty/>
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  8. badger5
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    badger5 RIP S3dave Site Sponsor

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    Nothing in my diary for monday.. as it happens its the only available day next week I have tho
    keep me informed...
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  9. badger5
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    badger5 RIP S3dave Site Sponsor

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    TTT Darren t

    Monday.........

    ??

    You call and book in for TODAY

    You then dont turn up Or contact at all

    Do I summarise this correctly?
    Last edited: Feb 25, 2013
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