1.9tdi AHU not starting unless boost control valve unplugged

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Iwallace
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1.9tdi AHU not starting unless boost control valve unplugged

Post by Iwallace »

Howdy,

At a bit of a loss so thought I’d come to the well of knowledge.
Tried starting up ready to drive to my MOT and no joy.
Well, it cranks and starts fine but runs all of half a second before cutting out. Had a look in the engine bay and could hear the turbo boost control valve clicking fast, unplugged it and starts fine and drives just slow obviously.

Any ideas? Only thing recently I replaced a fuse for the heater fan(and switch) and fog light that’s all for the electrics

I’ve had issues for a while with massive power loss, feels like my old 1.6d, but I’ve narrowed it down to what I assume is bad injectors as I’ve just replaced the muffler and it left a mound of soot on the floor.


Van: 1990 2wd
Engine: 1998 1.9tdi AHU MK3 golf
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Aidan
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Re: 1.9tdi AHU not starting unless boost control valve unplugged

Post by Aidan »

have you fitted led bulbs at the back, eg reverse lamp ?
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Iwallace
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Re: 1.9tdi AHU not starting unless boost control valve unplugged

Post by Iwallace »

I’ve replaced both position lamps but not led, the reverse bulb is led but always has been since i bought it. How come?
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Aidan
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Re: 1.9tdi AHU not starting unless boost control valve unplugged

Post by Aidan »

SyncroAndy diagnosed a fault (through careful logical testing) on Mark Williams TDi with it going into limp, associated with the boost valve which proved to be something to do with led reverse bulb, I think it was due to common earth and voltage/voltage drop, which meant that the ecu wasn't happy with the signal it was getting hence dropping into limp mode on and off, if you restarted it was fine, till it went again, just thought it was a bit similar to your symptoms....
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Iwallace
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Re: 1.9tdi AHU not starting unless boost control valve unplugged

Post by Iwallace »

Blimey thanks would never have guessed.
It’s in the garage at the moment I’ll let them know
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Iwallace
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Re: 1.9tdi AHU not starting unless boost control valve unplugged

Post by Iwallace »

Aidan wrote: ↑09 Feb 2024, 07:43 SyncroAndy diagnosed a fault (through careful logical testing) on Mark Williams TDi with it going into limp, associated with the boost valve which proved to be something to do with led reverse bulb, I think it was due to common earth and voltage/voltage drop, which meant that the ecu wasn't happy with the signal it was getting hence dropping into limp mode on and off, if you restarted it was fine, till it went again, just thought it was a bit similar to your symptoms....

Managed to get it fixed, ended up being the immobiliser and was tripping because it was put in the cavity and water leaked in.
Immo bypass soldered in and all perfect now.

Found with VCDS scan
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