Technical EGR Solenoid fix

[nigelvan]

So, I'm trying to figure out if and what is wrong with the EGR solenoid valve.
Using my mouth I seem to be able to suck through the VAC pipe from the other side (normally connected to the EGR valve)
I disassembled the solenoid valve because I read on this forum it's probably broken due to age and water ingress. It didn't look to good though.
Now I'm trying to figure out how it is supposed to work. The solenoid is still working and the resistance is fine (about 5 ohm)

I cleaned the rest of the EGR system and it seems the EGR has been operational.

Anyone who can tell me more about the operation of this solenoid valve?

 

[Anthony489]

Hi Nigel

This is my interpretation of operation:

The valve has 3 ports, Input Vacuum, Atmosphere (with little foam filter), and Output Variable Vacuum. Inside is a rubber diaphragm that allows the Output port to communicate either with Input Vacuum or Atmosphere. The diaphragm is moved by the solenoid pull acting against a spring. The ECU drives the solenoid with a pulsed waveform at 140 cycles per second (Hz), and by varying the duty cycle between 6% and 60% it can vary the percentage of time connected to each port. In this way the output vacuum can be smoothly varied anywhere between 6 and 60% of Input vacuum (i.e. 60 to 600 mBar below atmospheric). With no electrical drive the Output port communicates with Atmosphere.

As the internals are jigging up and down the whole time, it's a buzzy little beast so is mounted on rubber isolators to avoid noise being transmitted through the bulkhead. I guess the diaphragm may eventually get tired after long service.

The coil is 5.5 ohms nominal, and draws an average of 1 amp at maximum duty cycle which implies the drive voltage is about 9 volts.

I guess the output vacuum has a bit of pulsation, but the EGR valve it drives is too slow to respond to the pulsing and will just average things out. With no vacuum (e.g. solenoid drive disconnected or tube pulled off) the EGR valve is fully closed.

 

[nigelvan]

Hi Anthony,
Thanks once again! at 12V the solenoid draws about 2A so according to the 60% duty cycle this could match. I can confirm the solenoid is working.
So the coil does two things I think: It pulls down the membrane which is in a separate compartment. 2nd it pulls the round metal plate with holes down on to the Atmosphere running through the center of the coil. On top there is a (weak) spring, I suppose this metal plate gets sucked upwards against the spring by either the Vacuum or Output as the EGR valve closes.
Do you know how I can test if this part is working ok? The ECU seems pretty laidback about the whole EGR thing ;-).

 

[Anthony489]

Hi again

I'm quite surprised you managed to get the valve apart - they look like they are glued/bonded together.

I wouldn't apply 12 volts (at effectively 100% duty cycle) for too long as that's 26 watts and you risk overheating the solenoid winding. In normal operation the most it sees is about half that.

The only way I can think of testing it is to put it back in situ and tee in a vacuum gauge to the output pipe. One of those manifold gauges people used to fit on their dashboard in the 1960's would do if you can pick one up cheaply, or the sort sold new for various tests on engines. With a long bit of pipe you could rig it up where you can see it when driving. The EGR valve is opened mostly under light cruising conditions.

If you are more interested in getting things working than satisfying your curiosity, you might be better off just fitting a new one. In the UK they are about £50.

 

[nigelvan]

It's not so hard to open it up. I used a heat gun at 260-280C to soften the plastic a bit so it can be pried open without damaging the clips too much.
I thought it would be easy to figure out if and what was wrong but it's quite hard to test the part without putting it back together.

I thought about fitting a new one, but it's 70€ here at least for a quality part and I read that disconnecting the EGR valve from the solenoid entirely also works with some benefits to the fuel economy. A friend with the 2.3 claims it's 1L/100km.

At idle the solenoid is also driven as the coil gets a bit warm, but at that RPM the vacuum seems too weak to do anything with the EGR valve itself...

 

[LandyAndy]

It's not so hard to open it up. I used a heat gun at 260-280C to soften the plastic a bit so it can be pried open without damaging the clips too much.
I thought it would be easy to figure out if and what was wrong but it's quite hard to test the part without putting it back together.

I thought about fitting a new one, but it's 70€ here at least for a quality part and I read that disconnecting the EGR valve from the solenoid entirely also works with some benefits to the fuel economy. A friend with the 2.3 claims it's 1L/100km.

At idle the solenoid is also driven as the coil gets a bit warm, but at that RPM the vacuum seems too weak to do anything with the EGR valve itself...

If you just remove the pipe from the vacuum pipe work that will stop the EGR operating but will cause problems as the throttle body will still be closing when it thinks the EGR is operating. if you want to stop it working remove the electrical connector off the vac solenoid, that will stop the system working including the TB closing. But it will bring on light on the dash.

This is based on an X250 Ducato.

 

[nigelvan]

If you just remove the pipe from the vacuum pipe work that will stop the EGR operating but will cause problems as the throttle body will still be closing when it thinks the EGR is operating. if you want to stop it working remove the electrical connector off the vac solenoid, that will stop the system working including the TB closing. But it will bring on light on the dash.

This is based on an X250 Ducato.

Correct, but according to this thread people claim it all works without affecting the TB (which I replaced last year)

 

[LandyAndy]

Correct, but according to this thread people claim it all works without affecting the TB (which I replaced last year)

All I can say is that on my X250 130 09 year. That with older, and newer style throttle body. No warning lights on. That the throttle bodies both close to a degree every time the EGR vac solenoid is operated. This I have physically seen by myself. This wasn’t an issue with a jammed open EGR, but once the blanking plate was installed, this created very bad engine running as the air intake can be closed to 95%, and the engine is constantly struggling not stall.

The only ways to stop this is unplug solenoid, but this brings dash light on. You can unscrew the throttle body valve flap and leave this permanently removed, but this stops the soft stopping that is the only other TB use. Or just get the EGR mapped out the system.

That’s my experience

 

[nigelvan]

All I can say is that on my X250 130 09 year. That with older, and newer style throttle body. No warning lights on. That the throttle bodies both close to a degree every time the EGR vac solenoid is operated. This I have physically seen by myself. This wasn’t an issue with a jammed open EGR, but once the blanking plate was installed, this created very bad engine running as the air intake can be closed to 95%, and the engine is constantly struggling not stall.

The only ways to stop this is unplug solenoid, but this brings dash light on. You can unscrew the throttle body valve flap and leave this permanently removed, but this stops the soft stopping that is the only other TB use. Or just get the EGR mapped out the system.

That’s my experience

Thanks, this is valuable information. I put everything back together and did a thorough test drive including cruising at 60 and 80 km/h and heavy acceleration (I do love the 3 liter) and everything seems fine. The solenoid was definitely working before. The only thing, in my opinion, what could get stuck overtime is the metal plate allowing the EGR membrane itself to 'relax' back in closed position. I guess long term fuel consumption will tell me more wether this 'fix' was necessary...

 

[nigelvan]

With a friend in Germany we did a comparison between a new part, and refurbished one (opened it up and cleaned). No difference. Either it doesn't brake so easily and is repairable (with some patience), or it doesn't play an important role.

 

[nigelvan]

Hi Nigel

This is my interpretation of operation:

The valve has 3 ports, Input Vacuum, Atmosphere (with little foam filter), and Output Variable Vacuum. Inside is a rubber diaphragm that allows the Output port to communicate either with Input Vacuum or Atmosphere. The diaphragm is moved by the solenoid pull acting against a spring. The ECU drives the solenoid with a pulsed waveform at 140 cycles per second (Hz), and by varying the duty cycle between 6% and 60% it can vary the percentage of time connected to each port. In this way the output vacuum can be smoothly varied anywhere between 6 and 60% of Input vacuum (i.e. 60 to 600 mBar below atmospheric). With no electrical drive the Output port communicates with Atmosphere.

As the internals are jigging up and down the whole time, it's a buzzy little beast so is mounted on rubber isolators to avoid noise being transmitted through the bulkhead. I guess the diaphragm may eventually get tired after long service.

The coil is 5.5 ohms nominal, and draws an average of 1 amp at maximum duty cycle which implies the drive voltage is about 9 volts.

I guess the output vacuum has a bit of pulsation, but the EGR valve it drives is too slow to respond to the pulsing and will just average things out. With no vacuum (e.g. solenoid drive disconnected or tube pulled off) the EGR valve is fully closed.

Hi Anthony and other thread followers,

At this point, it's 100% my curiosity and not trying to fix the EGR solenoid valve... As after a few 1000km into Europe I'm quite sure it's not doing what it's supposed to be doing, either it's opening my EGR when it shouldn't, or it's closed all the time. Hard to tell with no real indications (no smoke, no loss of power, fuel consumption is about what I'm used to have: 10.4L/100km in mountainous areas) although it's quite possible it's been broken for as long as I had the van... It's too hot to touch after a drive... Anyway, I'll get a replacement from the moment I can find an address to have it send to. Should've done this way sooner, but again, I didn't know...

But, in another episode of curiosity, I opened it up once more to check the inner workings. I did find a clogged valve at the center of the membrane that I missed last time, and cleaned it. So, the VAC line will suck the membrane upwards if the valve is unpowered. the VAC pipe that comes into the housing below the center of the membrane (top of the unit) will push a little valve down that opens and connects the OUT line with ATM. This is the off, EGR closed state I reckon.
But, and here's where I get lost, when the solenoid is powered during the PWM cycle, the only thing it does is closing off the ATM with a metal plate getting pulled to it, and I'm really wondering what pulls the membrane down in order to connect VAC with OUT. The membrane and plastic part are not magnetic so the solenoid has no direct impact on that. The only thing I could be missing is if the center part going through the solenoid is supposed to move, and if that's the case, would pull a vacuum inside the housing to suck the membrane down or something... Anyway like I said, it's just curiosity.

 

[nigelvan]

Guys, an update: I did replace the solenoid unit and I can tell the difference because engine sound slightly changes when it opens/closes. Also there's suction on the ATM end. If you put you finger on an block the air I think the EGR opens because the engine sound also changes. So far not really a difference in driving. But it seems fuel consumption went down. We did a lot of cruising in France lately, with low load on the engine and I got to 9.5L/100km. Before in Belgium (flat but a lot of highway) I was at 10.2. Before the installation of the solenoid I drove with the vaccuum hose disconnected and never got below 10.5, rather close to 11. In Greece it was even higher probably because of fuel quality maybe?
This was measured using the Fuelio app and real consumption, not what the computer tells me (it's always wrong).