Pressure Transducer, 2.1TD location

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RaceMouse
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Pressure Transducer, 2.1TD location

Post by RaceMouse »

Hi there,
Anyone knows how to verify the functionallity of the pressure transducer for the waste gate control ?
If I have my hands on the correct part, it is a small green plastic thing mounted next to the cooling water expansion container. It has two wires and two hoses. When I measure the resistance between the two wires, it is very constant whether I suck or blow in the hose that goes to the inlet manifold. Should that be normal ?
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RaceMouse
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Kowalski
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Post by Kowalski »

Are you sure it is a pressure transducer and not an electrovalve you're blowing through?
If it is a transducer, it'll be a pressure operated switch and probably needs 15 psi to operate it (which is rather more pressure than you can produce by blowing it).
RaceMouse
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Post by RaceMouse »

Could be. Could be. Indeed.
It _LOOKED_ like a pressure transducer :-)
If it is not a pressure transducer, where would it then be situated and what would it look like ?
(Xantia '96 - 2.1 TD)
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Kowalski
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Post by Kowalski »

Do they have one? The 1.9 TDs don't, the wastegate on the turbo is all built into the turbo.
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Post by fordsone27n »

Sounds like the ECU switched solenoid that controls the vacuum to the EGR valve to me. Having said that, on my xantia this is mounted on the bulkhead. I cant remember seeing any sensors on the turbo. Having said that the 2.1 is somewhat different I'm lead to believe.
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Post by RaceMouse »

I have to admit that it sound plausible to. Is there anyone who can describe how it looks like so I can find it and verify its function ?
/RaceMouse
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Post by fordsone27n »

Again, mine is a 1.9td, so dont take it as being right but the EGR solenoid is a small cylinder about 20mm high and 20mm diameter. It has a green plastic moulded socket on the bottom into which a light green two pin plug is connected. On top of the cylinder is two pipe connections. one pointing up, the other at 90 deg to it. One is connected to the vaccuum pump, the other to the EGR valve diaphram. On the 1.9 this solenoid is mounted on the bulkead near the LHM tank, on the same bracket as the fast idle solenoid, which, apart from small differences in the socket design to stop wrong connections is exactly the same.
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Post by RaceMouse »

Based on your answer fordsone27n, then what I had my fingers into defenetely seemed like the EGR solenoid.
The problem I'm trying to solve is that sometimes the turbo just stops working. When I read out the faults stored in the computer, one of the faults was "low inlet manifold preassure" (not the exact words but close). Therefore - if the sensor is only working some times it would explain why the computer is not always closing the waste gate. In order to get to the source of the problem I need to check the wiring around the various related components. That is why I need to find the pressure transducer.
What shape am I looking for here ?
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Post by fordsone27n »

Not sure on this one, because as Kowalski made reference to, and from my memory i'm sure he is correct, the 1.9's like we have, do not have any electronic control of the turbo wastegate. I thought wastegate is a spring loaded valve which opened as pressure in the exhaust side of the turbo increases this should even and limit the boost pressure throughout the engines operational range. All the egr valve on the inlet manifold does is allows recirculation of exhaust gases under various situations to reduce emissions. Its unlikely to significantly effect inlet manifold pressure.
Other contributors please correct me if i'm wrong.
Adrian
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Post by RaceMouse »

I'm sure you are not wrong there. The Citroen garage said that on the 2.1 TD is is electrically controlled, so your'e right :-)
I do, however, need to find the MAP sensor. Any suggestions anyone ?
Race
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Post by Doc »

Hi RaceMouse,
Is this a general interest or are you experiencing engine problems?
I'm not sure what car you've got but my 1992 XM 2.1 TD has been running around with the EGR pump solenoid/motor disconnected for the last 2 years. The car always runs and idles smoothly and has sailed through its annual MOT test/particulate smoke test for the last two years. I mention this as I cannot find the component you speak of near the coolant reservoir. I assume your car is either a more recent XM or a Xantia?
Apart from worn glowplugs making it a little difficult to start when cold (another awkward job to do tomorrow!) my XM averages 43mpg. Incidentally my engine has the Bosch mechanical fuel injection pump unit- no electronics and NO MAP sensor. The wastegate is also mechanically controlled and as long as it doesn't seize then all is well.
If your car has a pipe linking the intercooler (air to air) to the pressure valve on top of the pump, (enables extra fuelling when turbo on boost), make sure it's not chaffed or holed. Any leaks here will prevent turbo from boosting correctly.
Have you checked basics like air leaks into fuel supply and/or leak-off pipes from injectors?
Hope this helps
Doc
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Post by RaceMouse »

The question is because I have problems with the car. The trouble is that sometimes the turbo seems absent until ~2800 RPM. On other times the boost starts at ~2100 RPM. Here I can hear it starts to rev up and at the same time feel it (!). It seems to me to that the waste gate isn't closing. The Citroen garage told me that there was a MAP sensor and the waste gate is electically controlled and operated. When we read out the onboard computer, it told us that the inlet manifold pressure was too low.
The above is the reason why i'm trying to locate the sensor and find out if it is a loose connection or a bad sensor.
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