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Thread: Passat 1.9 TDI AVF wont start

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  1. Passat 1.9 TDI AVF wont start 
    #1
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    I wonder if you can help me with a problem I have with my passat. It's a 1.9 TDI 4 Motion engine code AVF.

    A week ago I discovered a tiny leak on the heater matrix which had been leaving an awful film on the windscreen. I’ve heard bad things about sealing products so bit the bullet and changed the matrix. This is a dash out job on a 3B6 variant. Massive task but I did it. The car started right away with no issues and I drove it a few miles thereafter without issue. I did notice however that the computer didn’t change displays with buttons pressed so I took the wheel back off to find Id left one connector disconnected behind. Reconnected, reassembled turned on ignition and pressed the button. All good. Did not start the engine.

    The next day my wife took the car out and after about 0.5 mile the car stopped. We towed it home and plugged in VCDS. There was a message relating to drivetrain communications and software versions mismatch which I’ve read are “random no harm codes” which can be cleared so I did and it has not come back but it still wont start. No other codes are thrown up.

    I proved it is not immobiliser by using a key without a transponder and it detected the lack thereof so I assume with a good key and no such errors the immobiliser is ok.

    I started thinking fuelling issues given it was running then stopped. Eureka I thought. I found that the lift pump in the tank was not running for a short time when the key turned to ign position. I then found that relay 167 in position 10 of the relay carrier had a problem. It was operating but no current was going to the motor. For diagnosis purposes I cleaned the contact and bent it a little (I’ll get a new one) and now the pump runs as expected. I guess when removing the relay carrier it accelerated an impending failure to fail now.

    So… I figured that with a bit of priming I’d be away but despite proving it pumps fuel out of the filter and then sucking fuel through the tandem pump with a hand vac pump she still won’t start. I find it really hard to believe that that after finding this “hard fault” there is still another issue, yet it would seem so.

    I tried looking at injection figures etc on the engine module whilst cranking and the numbers all jump around so I can only assume that the ECU is probably OK.. It’s got fuel (now) and it is probably primed OK after having “effectively running out of fuel”, I’m at a bit of a loss. BTW the flap to starve air on switch off is not closed off.

    Any pointers on this PD engine gratefully received.

    Thanks,

    Dave
     
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  2. Re: Passat 1.9 TDI AVF wont start 
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    charge the battery up

    if the starter doesn't turn over the engine fast enough, fuel wont be pumped into engine. Its around 250 to 280 rpm for fuel to be allowed to flow


    I am imagining that its been turned over a lot to fault find and not had a chance to start to recharge the battery
    VW POLO 2002 1.2 12v , Audi A6 2006 2.0 TDi SE , Skoda Fabia 1.4 TDi

    All 3 cars in the current fleet
     
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  3. Re: Passat 1.9 TDI AVF wont start 
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    Have you tried a GENTLE sniff of brake cleaner, and I mean GENTLE! If it does not give any fault codes you may just have an air lock.
    Anthropogenic climate change, the biggest con inflicted on mankind since religion...

    Slava Ukraini
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  4. Re: Passat 1.9 TDI AVF wont start 
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    When I forgot to fill a new filter up during a service, it ran for 10-15seconds, then stopped dead. even after priming it took a good 20mins of straight cranking before it coughed... starter cable for incredibly hot lol.


    54 Passat Wagon PD175
    99’ Audi S4 Avant 2.7 QTO
     
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  5. Re: Passat 1.9 TDI AVF wont start 
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    Thanks all for responses. Battery was recharged (and is being again now) but looking at the VCDS log I did tonight of various parameters I hoped would indicate the ECU was healthy, it shows it was only cranking at 170 -190 rpm max. It sounded healthy though.

    I've been working on the air lock theory but despite pulling fuel through with a hand vac it's made no difference. I've changed the fuel filter several times in my 10 years of ownership and never had any issues with priming. This is weird.

    I tried plugging the fuel line to the filter with a pressure gauge tonight and got about 6 psi with the pump running directly off a spare battery and wires. I can hear a bit of sloshing in the tank. As the fuel cannot be returning from the filter (with the gauge plugging supply the line) this can only be either a built in relief valve on the pump, or a leak off the pump. Anyone got any idea how much pressure this pump should deliver? My daughter has a Bora with similar fuel arrangement so I hope to compare soon but work is getting in the way.

    I haven't tried the brake cleaner trick yet mind you. What's the worst that could happen? I assume straight into the intake duct yes?

    Oh just thought of something else. When you power the pump up it doesn't "Buzz" so much. Very quiet other than the sloshing noise and it pulls about 3.5 amps.

    Thanks guys,

    Dave
    Last edited by davebrannigan; 03-07-2018 at 09:58 PM. Reason: Extra info added at end of post.
     
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  6. Re: Passat 1.9 TDI AVF wont start 
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    So the latest is:

    I put a gauge on my daughters bora and when you turn the key it builds to about 10psi and holds it after the pump stops, like there is a non return valve in the line. Using the same gauge the passat barely reads 2 and it drops off immediately when the pump stops. My conclusion is therefor ethat it is either the pump or a leak on the supply line inside the tank.

    Had a quick look in the tank and being a 4 motion there is a mess of pipes for transferring fuel from the left tank to the right using "suction pumps" according to elsawin.

    My job for tomorrow (as its getting dark now) is to watch the inside of the tank when the key is turned and see if there is a massive bleed somewhere. changing the pump looks a nightmare, but if it's one of the hoses that looks worse. All the lines are really hard/ brittle feeling and I'd be afraid of breaking one. If I have to remove the tank it involves removing the exhaust, the rear propshaft and the rear axle. Nightmare.

    Anyone done this on a 4 motion?

    Add insult to injury ECP are out of stock of the one that appears most similar to mine.

    Aaaarrrrgggghhhhh.
     
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  7. Re: Passat 1.9 TDI AVF wont start 
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    Hi!
    I know this thread is old but what did you end up doing? Was it the in tank pump that caused the problem?

    -S
     
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  8. Re: Passat 1.9 TDI AVF wont start 
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    Yes it’s been a while... but as feared when trying to remove pipes from the pump one did snap meaning I had to replace the pump. Not cheap. After doing so it still wouldn’t start but, long story short I found that giving it a good tow start got her running.

    The engine must crank at greater than a certain rpm in order for the electric pump will run and until it does the high pressure pump won’t prime either. Bumping it at 10mph in 2nd span it quick enough to start and it’s been fine ever since.

    So, sequence of events was,

    1 Heater matrix leaked and was replaced by removing dashboard.
    2 disturbing relays on removal of dash caused fuel pump relay to fail a week later.
    3 this basically caused an air lock in the fuel system as would happen if you run the tank dry.
    4 replacing the relay fixed the fault but I was left with an airlock and didn’t realise.
    5 in trying to diagnose that I broke a perfectly serviceable pump.
    6 bump starting it sorted the air lock
    7 been running fine ever since.

    life lesson. Just sorry I broke the pump else it would have been a cheap fix.

    hope that helps.

    Dave
     
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  9. Re: Passat 1.9 TDI AVF wont start 
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    Quote Originally Posted by davebrannigan View Post
    The engine must crank at greater than a certain rpm in order for the electric pump will run
    The engine must crank in excess or 280rpm for the fueling table in the ECU MAp to function, not the actual pump in the tank.
    Anthropogenic climate change, the biggest con inflicted on mankind since religion...

    Slava Ukraini
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