HDi Electro Valve

[citroenxm]

Hi all..

HDi models use an Electro valve to control a Vaccuum to operate the Turbo Wastegate.. HDi Wastegates are "Normally Open" at rest, designed that way as a fail safe, so in the event of any vaccuum fail, it will open and prevent overboost into the engine!

So, on HDi 110's there two of the electrovalves just up be the cam belt cover, ones for the turbo wastegate the other is for the EGR Valve...

The Wastegate boost is monitored by the ECU, however, the EGR valve has no monitor or pressure sensors on it at all, so a failed Electro valve wont be detected so doesn't matter if it works or not however the Wastegate one does matter in a BIG way.

If its failed, there will normally be no boost, you can also confirm this under the bonnet. With the engine idleing, rev the engine (The throttle is between the air inlet pipe and the LHM tank) the Intercooler pipe across the front of the engine will BULGE under boost, however, if the electro valve is not working, the intercooler pipe will "Pinch" as the engine sucks air quicker then it can be fed!!

The first thing you can try is to swap the two eletrovalves over, be sure to connect the Vac pipes back the same way... and repeat the above test.. if it still buckles then both are dead, but REALLY you only need to replace the Wastegate one.

I opened one of these valves up tonight to have a look, but didn;t get too far..







The circular item with the spring on top of it in the first pic is the device the controls the vac from one spigot to the other.... buy simply being pushed upwards or down with the springs and the soilinoid thats fited under it. Ive not worked out how the relay/solinoid works yet as Ive no 12v DC supply at home.

[Chlorate]

I did notice Paul...Honest!

I've autopsied mine like you did, it's an odd bit of kit.

Stuck a multimeter on the pins and it had a resistance of about 17 ohms, no idea whether it's supposed to be like that but at least it's not an open circuit.
I attempted to get it to make some sort of noise by brushing the contacts with 9 and 18v but it was silent as the grave apart from a few sparks. However it may not be straight up DC that it's looking for...

Without being able to get any further into it than you did, it seems that the atmospheric intake on the bottom is the key.

Although I still haven't worked out the exact mechanism of how it does it...

One thought was that the little filter at the bottom of the valve is gunked up, so I removed it and left it open to air and I seem to get turbo whistle now, although I can't tell whether that's because I'm listening for it or it's actually done the trick. Either way the management light is still on and I didn't take it for a test drive...

[citroenxm]

I think the "Solinoind" lifts and lowers the tranparent disc, as the two upper turbes where the vaccuum is directed to the wastegate and away, are controled by the transparent disc... against the top its blocked off, lowered its directed to the wastegate...

I also got sparks with a 12v dc supply.

If the engine was running and a turbo whistle, then the wastegate has closed... Simply revving the engine should expand the intercooler pipe QUICKER then the engine sucks if its working... otherwise, the engine sucks the intercooler pipe inwards if theres no boost comming through..

The ECU light will self cancel after a few moments or so after it detects over boost...

If your getting over boost it sounds like the solinoid is/was sticking on direct to wastegate and holding it closed... hence overboost

[Old-Guy]

Fortunately, my old XUD doesn't have such complications, so I haven't got any vacuum electro-valves to pull apart. Looking at Paul's nice clear macro photos, my educated guess is that energising the solenoid coil (DC) pulls the disc assembly away from the two pipes, opening the valve against spring pressure. There has to be some arrangement to allow pressure (vacuum) equalisation across both sides of the disc without a mighty vacuum leak as the solenoid would have to pull a huge current to overcome even a modest vacuum. I'd further guess that the equalisation path is through the middle of the disc assembly and the red 'rubber' moulding that incorporates the air filter mesh looks suspiciously like it seals with something. The disc has to be a reasonably tight fit in the body yet still move reasonably easily.

So I'd expect that the most common reason for one of these valves not working properly would be old-fashioned DIRT rather than electrical failure - the only electrical component is the coil which either conducts (OK) or doesn't (scrapper)! The disc assembly has to move freely, and the pressure balance path (including the mesh filter has to be clear. I'd try dismantling an inoperative valve as shown and giving it a thorough clean inside before reassembling - without any lubrication that would just trap dirt!

[citroenxm]

Thanks Guy..

The valves are actually generally very reliable.. Mine has NOT given an issue at all, from 156k to 244k SO FAR!!

Ill reassemble this one now it looks clear, and stick it on my car and see what happens..

[KennyW]

Hi Guys,

Reading both posts with interest, can I confirm one thing. Does the 90hp HDi have these values fitted or is t the 110hp only

Kenny

[citroenxm]

The 90 has a different turbo which i dontt think uses a vaccuum operated wastegate. I think they use a pressure sensing wastegate same as the old xud..

[Chlorate]

I tried to get further into mine now that I've taken an unexpected day off work and ordered up a new part...

No chance, they appear to be made by assembling the innards and casting the plastic around it, I've exposed a bit of metal with a junior hacksaw and a screwdriver but have given up there.
I wish my Dremel hadn't been adopted by the university now...