turbo warning light

[freek]

Hi,
I own a BX trd turbo since 13 years now. Until recently I never saw the turbo pressure light illuminate. But now when I drive over 130 km/hr and want to accelerate the light goes on. The acceleration is normal. When I slow down again the light switches off immediately. Can the pressure sensor be the cause? How does this device work? I know that the sensor is operated by a vacuum hose from the fuel pump and I assume that the sensor operates the waste gate. But what drives the warning light?
Thanks for reply!

[jeremy]

Sounds like your wastegate on the turbo has stuck. As you know the turbo is an exhaust driven air pump and the wastegate operates to limit the maximum output. The pressure in the induction system is communicated to the extra fuel device on the injection pump bu the thin rubber hose running from the front of the intercooler to the unit on the front of the pump body. There is a 'T' piece in this pipe which is connected to a smaller pipe which runs to the warning light switch which is under the battery.
The wastegate is purely mechanical in operation with no electrical commections. Some have a link visible from under the car - it may be that moving this manually will clear the obstruction but my guess is that you will have to replace the turbo itself as its probably heavily corroded.
What happens if you ignore it? Not much I suppose except excess pressure. This will not produce any extra power unless the additional fuel device is adjusted to increase its delivery. If you search this site you will find a few owners have increased the performance by increasing the boost pressure and modifying the extra fuel system.
jeremy

[freek]

Thanks again Jeremy. The turbo is a GARRET, which according to Haynes has a waste gate actuator as a seperate unit. I hope this means that I can test it by hand. But I still hope that the sensor is guilty. It won't be the first time: once, a long time ago, when the engine was warm the overheating warning light warned that there was something wrong with the cooling system. After examining the system I decided to mount a new radiator. But this turned out to be splilled money. It turned out to be a faulty sensor..... An expensive lesson!

[jeremy]

You could fit a boost gauge. I'm thinking of fitting one to my BX TD and think it would be useful in letting me know when the thing would accelerate properly for overtaking!. I know the question is where to put it - and I fitted atemeperature gauge to a pod fitted on the side of the instrument binnacle. This is actually quite a good place as its visible outside my hand whan driving. The engine end of the boost gauge is simply a T into the pipe from the front of the intercooler.
jeremy

[oilyspanner]

Does the car drive normally otherwise, if the wastegate has stuck it should produce more boost then it should, without the extra fuelling to go with it it should still go faster than it used to! but watch out, if the thing drives normally, running out of puff after 4500 rpm or so then it points to the switch, I have a boost gauge fitted to mine (pod on RH side of dash with the water temp gauge) and it seems to have a maximum of around 13 psi when under maximum load (flat in 4th up a big hill!) If your actuator has jammes it should just be possible to see it with the front of the car on ramps, perhaps a squirt of penetrating oil on the linkage and a few graunches back and forth will do the trick (it doesnt move far anyway)
Stewart

[freek]

I did not have time yet to look underneath the car. But driving it today I found out that the light appears between >3000 and 4000 rpm in every gear. It dimms with further accelerating because of the rpm limit. I do not notice extra power (or less) what so ever. The engine behaves as usual. So may be it isn't the wastegate afterall. As soon as I have time to look at the parts in question I will tell you what I found. Regards, Freek