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Thread: ALH TDI VE injection pump quantity adjuster test?

  1. #11
    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by Cory.Miller View Post
    I’ll have read more about ECU tuning and the risk of loosing the warranty before playing with that more.
    I wouldn't. If it's been "fixed", it's got an awesome warranty on all the complicated and expensive emissions stuff. But the problem with "fixing" them is that the fix is hard on all that complicated and expensive emissions stuff, and you'll likely need that warranty.

    We have a 2015 Touareg with what's essentially the same engine as your A6. We've had it since new and I'm really torn as to whether I should allow it to get "fixed". We've got until the end of the year to decide...

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  2. #12
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    Here's an update for anyone still following this....
    the Bosch VE injection pump is taken apart and I have confirmed than in the high pressure section there are no obvious mechanical failures or wear. After much additional research including finally finding the pump operation manual, I'm certain I understand the details of the pump's functional requirements and am left with the follow conclusions:
    1. The broken case pressure relief valve (aka pressure control valve) seems like the most likely culprit to my crank-no start issue. Since this issue developed suddenly and didn't get progressively worse like many instances I've read, it seems plausible that this valve "let loose" in a more extreme way than normal (press collar full drop) which created the instantaneous no start condition. The jammed collar resulted in a seizing the lower half of the case pressure relief valve which caused it to break in half during removal. The break in half caused the removal to slightly damage the threads which led to an crooked installation of the new valve and caused the second one to break. I'm hoping that the next valve I install very carefully will solve the problem.

    2. I do wonder if the "overflow restriction valve" in the fuel return fitting at the top of the pump could prevent enough fuel flow for engine start if the valve is plugged. without have a pressure drop spec, I cant test it, but it seems pretty restricted when I try to blow through either end. When reading that case pressure of around 30 psi should be maintained while flowing sufficient fuel through this valve back to tank, it seems plausible that the tiny orifice could be mostly plugged which could mostly dead head the low pressure side of the pump and thus starve the high pressure side. I'm debating if I should buy one now to eliminate this possibility, but I think I will wait and try conclusion 1 above first as to not change 2 things at once. Thoughts on this theory would be helpful.

    3. I've read that the start of injection timing solenoid failure can cause what I observed just before the engine died and wouldn't start anymore (without starting fluid). It ran rough and smoked. After much reading on forums about this and reading pages 54 - 57 of the Bosch VE pump operation manual linked above, it seems possible that this solenoid could fail to open (normally open) which causes the injection timing to be fully retarded which seems like it would make the engine run rough and produce lots of white smoke with the injection being too delayed. But I don't think failure of this solenoid valve by itself would cause my no start issue. Plus, if it were failed I should be getting a couple of related engine codes. Since I can't verify operation of this valve without using a full can of starting fluid to run the engine while logging vag-com start of injection graph, I can only check resistance through it which is between the 10 - 20 ohm range I read is expected. So I don't think this solenoid valve is bad (good thing since it's about $300).

    3. The fuel quantity valve seems to move freely and since I verified it moves to the mid range of control when the key is tuned on, I expect this is functioning normally.

    4. After reading in the manual (linked above) about the "delivery valve" inside each of the high pressure injection line fittings in the high pressure pump body, I don't think these could be the problem. They are basically a check valve designed to open at a certain high pressure when given each burst of fuel per ignition event, then close to keep the high pressure fuel line at case pressure until the next injection pulse.

    So without further input, I'll be putting this pump back in, changing timing belt water pump and pulleys while in there, then putting the new case pressure relieve valve in when it arrives later next week and giving it a try. I can't wait to get this thing solved so I can focus on upgrades to my Audi A6 TDI! Thanks all for the input.
    2002 VW Jetta TDI MKIV
    2014 AUDI A6 (C7) TDI

  3. #13
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