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Thread: No throttle response when cold onTDI300

  1. #1
    Join Date
    Sep 2010
    Location
    Branxton NSW
    Posts
    490

    No throttle response when cold onTDI300

    Hi guys,

    Yesty I took the disco to work (after sitting in the shed for about 2 weeks) and I noticed 2 things that are a bit worrying.
    1) Its very hard to start, when I bought it it was a matter of hitting the key after the glow plug light went out, and it would fire and stop, hitting the key again would kick it into life and away she went.

    2) probly the more concerning one, it was VERY doughy off the line, to the point where I found myself in the middle of an intersection with no go!
    After going through a Give Way and trying to accelerate out the other side, it was as though the pedal wasnt conected to anything, it would just idle realy rough and not rev up with throttle application.
    Did it again on the way home, in the middle of the highway, much more concerning, pumping the pedal did nothing, and only a very slow gentle application would bring the revs up sufficient to actually get the car moving.
    After the car warmed up, it was much better, as per normal I would assume but not owning any other Diesel vehicles im only assuming.

    Over the last few days I have fitted a few gauges (boost, water, egt, oil) and was wondering if tapping my boost gauge into the wastegate actuator line could be causing the problem???

    Im not terribly adept in the area of diesel engine, hence why I bought this to learn.

    I did a quick search last night and people seemed to be pointing the finger at the lift pump? true or false???
    Much thanks!

    Robert.

  2. #2
    Join Date
    Sep 2010
    Location
    Branxton NSW
    Posts
    490
    Just had a quick fiddle in the shed, it seems quite weird to me...

    If you hold the engine at constant revs (when cold) say 1500 for a few seconds and then let the throttle snap shut, the revs die down, and the engine then gets a little canter (rough running) at this point U can push the accelerator pedal flat to the floor and the engine just idles, a few seconds later the revs start to pick up ever so gradually...

    I can re-create the problem time and time again but it seems to be less prevelant when the engine gets closer to operating temp.

  3. #3
    Join Date
    Jan 1970
    Location
    watch this space.....
    Posts
    12,260
    Dodgy lift pump ?

  4. #4
    Quote Originally Posted by rick130 View Post
    Dodgy lift pump ?
    Either that or a small air leak (e.g. air leaking in overnight).

  5. #5
    Join Date
    Aug 2006
    Location
    Melbourn(ish)
    Posts
    24,472
    loss of supply fuel pressure to the injector pump...
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    TDI D1(its responded well to its lecture about poor performance)

    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.

  6. #6
    Join Date
    Sep 2010
    Location
    Branxton NSW
    Posts
    490
    I have done a little searching on the site as I considered fitting an electric lift pump in place of the mechanical one, and I read that the lift pump isnt critical to the operation of the system, the injector pump will be able to suck enough fuel by its self. Fact or Fiction? I did just drive the car back from Syd last month and had no problems or rough running, and the performance seemed fine, although I have nothing to base this on, so could it be something more sinister?

    Is there a cold temp compensator, to richen her up untill operating temp? or do diesels not have such a thing?

    I am heading to my parents house over the weekend to show of the new toy and dont REALLY want to make an SOS call if she fails to proceed!

    Any other suggestions?

    Cheers,

    Robert.

  7. #7
    Join Date
    Aug 2009
    Location
    lota, brisbane
    Posts
    578
    fuel filter/s

  8. #8
    Join Date
    Aug 2006
    Location
    Melbourn(ish)
    Posts
    24,472
    yep you can replace the mechanical pump with an electrical one dont rely on the injector pump pulling the fuel through all by itself but yes that will work.
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    TDI D1(its responded well to its lecture about poor performance)

    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.

  9. #9
    Join Date
    Jan 1970
    Location
    watch this space.....
    Posts
    12,260
    Quote Originally Posted by Phat-Customs View Post
    I have done a little searching on the site as I considered fitting an electric lift pump in place of the mechanical one, and I read that the lift pump isnt critical to the operation of the system, the injector pump will be able to suck enough fuel by its self. Fact or Fiction?
    [snip]
    fiction IMO, from what I've seen the lift pump needs to be working properly to supply enough fuel for the injector pump.
    I've heard too many stories of dodgy lift pumps causing problems.

    Is there a cold temp compensator, to richen her up untill operating temp? or do diesels not have such a thing?

    I am heading to my parents house over the weekend to show of the new toy and dont REALLY want to make an SOS call if she fails to proceed!

    Any other suggestions?

    Cheers,

    Robert.
    Supposedly the pump advances for cold starting and running, it senses water temp and pulls the advance lever on the pump.
    I can't see any connections or water temp sensors on my engine or pump though.

    The TDi is pretty doughy when cold too, they take a few minutes to warm and get percolating.

  10. #10
    One of the guys in the LROCB had a failed lift pump, and the engine was heavily down on power (hot and cold).

    I have had diesels that somehow such some air into the fuel overnight, and they will either not start or start and run rough till it is cleared.

    Does the engine blow more or less smoke on startup than it did before?

    EDIT: IDI diesels are completely gutless untill warmed up. DI diesels are not as bad, but as Rick said - pretty doughy till warmed up.

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