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Help , very hard to start my 1994 Coupe 16v .

Discussion in 'Classic Audi Forum' started by MHage, Oct 25, 2005.

  1. MHage
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    MHage New Member

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    Please has anyone any suggestions , my 1994 Coupe 16v ( 140,000) will not start sometimes from cold or warm/hot .( but sometimes will start straight away )There is a spark , seems to be fuel pressure in the line it will eventually start by putting foot full on accelerator and turning it on the battery for ages and it just catches before my battery gives up !I have replaced the fuel distributor , cold start valve , idle stabilisation valve ,checked the air intake boot for leaks , removed checked and replaced the various emmissions pipes thinking there could be a vacuum leak .When it starts it revs freely but does sometimes has a slight flat spot when I rev it on idle as if its not getting fuel ( delay). I just warmed it up , switched it off , now it wont start again !!! I'm at my wits ends , looks like I'll have to take it to the main stealers unless I get some response , many thanks in advance to any suggestions , cheers.
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  2. Rev-head
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    Rev-head Active Member

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    something challenging for a change...........

    Have you replaced the fuel pump?.blocked Fuel filter causes the same problem.....

    Look forward to your reply

    Steve
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  3. MHage
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    MHage New Member

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    Thanks for your response , I have not changed the fuel pump ( in the tank is this correct as on my previous Audis they were underneath by the filter ) but I have changed the fuel filter and accumalator next to it .I am so concerned that I have carried out a compression test which gives 170 psi on all 4 cylinders which I pressume is good . BUT i noticed the spark plugs were black with soot ( not wet )when removed to do the test , strange as i have only just renewed them ! there is a rich smell coming from the car too so I changed the lambda probe yesterday but still the same problem !I am starting to think it is the ECU , what do you think ?
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  4. Rev-head
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    Rev-head Active Member

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    If your plugs are black there is not a fuel problem ,were all of them the same?....i would check your coil out and see if its at fault...mate had the same problem and ended up been the coil been been all burnt out inside ..caused the car to have flat spot because the harded the coil had to work it lost all timing..same thing when starting up.......maybe something to check out.have you any mates with same car or same age audi?
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  5. MHage
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    MHage New Member

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    Thanks again , I will try and get a replacement coil to see if theres any difference before doing anything else . I will let you know how I got off , best regards , Martyn.
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  6. scotty33
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    scotty33 Member

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    I had similar symptoms on an 87 80 with k jetronic. The fuel pump relay was the problem. I found that unplugging the relay seemed to 'reset' it. When plugged back in the car would then run ok - until the next time!
    Hall senders also seem to be a weak point on 16v's, if the ignition side of the ecu malfunctions, the fuel side will not start. You then get fuel pressure in the supply line, but not going to the injectors I think?
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  7. MHage
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    MHage New Member

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    Thank you , I have checked the car out again today , I have pressure to the fuel distributor and going to the cold start valve but no pressure to the 4 injectors supply lines ! Sounds like what you have told me , where is the hall sender and what does it look like , do you think its this or the ECU , thank you.
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  8. scotty33
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    scotty33 Member

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    Hall sender is in the distributor, Audi will probably want to sell you a complete dizzy for£££. I don't know how to test them, maybe an autoelectrical shop could do this? Try probedistributors.co.uk for replacing the hall sender in yours.
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  9. MHage
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    MHage New Member

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    The only thing I am confused about with regards the Hall sender is the fact that I have a healthy spark at the plugs , surely if the Hall sender has gone then I'd have no spark or am I wrong .
    I've checked again after work today and I have definate pressure at the fuel distributor and 5volts at the side plug once ignition is switched on , the only place where theres no pressure is in the 4 lines going to the injectors from the top of the fuel distributor . I removed all 4 lines from the top of the fuel distributor , turned the engine over and NO fuel came through , surely petrol should be gushing through. I have already changed the fuel distributor for a known good one . Can you explain whats happening please please, please.
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  10. scotty33
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    scotty33 Member

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    I'm no expert, I just read this stuff on another forum. I guess there is a solenoid valve inside the metering head that needs to be energised for fuel to reach the injectors. If there is a problem with the Ignition side of things, the fuel system does not operate either.
    I know it is generally very difficult to read fault codes from the 16v. Some have managed it though and the fault comes up as 'crank position sensor' There is not one as such, the only device that gives an engine reference position is the hall sender have a look at some of these:http://www.audifans.net/modules.php?name=Forums&file=search&mode=results
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  11. MHage
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    MHage New Member

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    Does anyone know if the hall sensor is faulty ,will there still be a healthy spark at the plug .
    Update- I have checked fuel pressure by fitting a guage in the fuel line ,( fuel cant go anywhere , deadheaded )and on ignition reads 120psi.
    It will eventually start (only just) before the battery gives out and when running sounds lumpy and smells rich then eventually stalls if let to idle , then cannot restart.
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  12. OutLore
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    OutLore VOIP Dude

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    [ QUOTE ]
    Does anyone know if the hall sensor is faulty ,will there still be a healthy spark at the plug .
    Update- I have checked fuel pressure by fitting a guage in the fuel line ,( fuel cant go anywhere , deadheaded )and on ignition reads 120psi.
    It will eventually start (only just) before the battery gives out and when running sounds lumpy and smells rich then eventually stalls if let to idle , then cannot restart.

    [/ QUOTE ]

    I had a similar problem with a V6 2.6 - turned out to be a new set of ignition leads required.

    I was getting a spark when turning it over, but had the same thing when it eventually started - would run like a dog for a while, then clear, then might start to misfire again later in the journey. I only noticed the lead problem because I had the engine cover off and it was playing up one night, I looked under the bonnet and it was like a fireworks display - 3 of the leads were shorting out to the engine and therefore the spark wasn't strong enough at the plug to ignite the fuel mixture.

    Audi wanted £100+ for new leads.... spoke to a mate of mine who worked for MSD at the time and he got me a set of V6 Vectra leads, which worked a treat....
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  13. MHage
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    MHage New Member

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    Thanks ,I've just had a look in the dark ,( the neighbours are expecting the funny farm to collect me anytime ! ) but sadly it looks good .
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  14. scotty33
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    scotty33 Member

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    I just reread your original post. My father in law's 93 16v passat had a similar problem but only when hot (I think).
    It would drive ok, for a while then suddenly lose power and chug like a site dumper at about 500 revs. moving the throttle would not make any difference
    except full throttle where it would rev up as normal. turned out to be strained wires on the lambda probe.
    I now know that the lambda has no effect until an engine is warmed up, then
    closed loop operation kicks in where lambda readings control mixture. But at
    full throttle, the lambda does not control mixture.
    Sounds similar to yours, but I can't see why yours won't start from cold?
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  15. scotty33
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    scotty33 Member

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    I now notice that you already did the lambda probe, so that should be ok...
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  16. MHage
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    MHage New Member

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    Thanks again , I'm going to check out all wiring under the bonnet today for possible breaks , bad connections etc .
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  17. scotty33
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    scotty33 Member

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    I would try running the car on easy start,
    sprayed straight into the throttle body.
    Only try it when the car won't start normally, then you'll know if its fuel or
    ignition.
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  18. MHage
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    MHage New Member

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    Problem solved at last , after changing the distributer , no difference , the ECU , no difference, I turned my attention to the temperature sensors as sometimes my temp guage reads when it wants to and this needed to be sorted at some time anyway , but the sensor which gives the guage a reading is the 4 pin one located in the head take off elbow which apparently has nothing to do with the ECU so instead I changed the small 2 pin sensor located under the distributor at the rear of the head and hey presto its working a treat once again.I will get around to changing the 4 pin sensor but I have been quoted over £71.00 from the main stealers ! anyone got a good used one for a fiver ?!!!!!!
    Many thanks for the kind people who spent time in helping me on my way , cheers . Oh yes , I have another query that I will post asap , thanks again.
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