Stuck Quantity Control Valve

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MercTech20
Newbie
Posts: 7
Joined: Sat May 13, 2023 6:20 am

Stuck Quantity Control Valve

Post by MercTech20 »

Here I have 2 waveforms, one from a stuck quantity control valve and the other I took after cleaning the valve and it made it to work again. This is from a Mercedes W212 with om651 engine where the diesel was contaminated and there was still no rail pressure after cleaning the system.
Are those irregularities in the waveform of the working valve caused by the mechanical movements of the valve. If so, then its possible to confirm a fault in this or the rail pressure regulator valve using the waveform.
Does anyone have other testing methods without having to remove half the engine compartment to get to this valve?
Attachments
OM651Good.png
OM651quantitycontrolBAD.png

picowight
TwoWaves
TwoWaves
Posts: 161
Joined: Sat Oct 26, 2019 6:45 pm

Re: Stuck Quantity Control Valve

Post by picowight »

I often use the current waveform of rail pressure regulating valves, solenoids, position motors etc - pretty much anything you would expect to move smoothly, to detect if it is sticking from a current anomaly. In the case of EGR and VNT the ECU will often cycle them stop to stop at ign on/off. Even if they are on a fuse that has a bunch of other things on you can use a fuse loop and command it with a scanner - if it's the only thing moving you can see it.

This was an intermittent stall on a CRV, had pages of this
2023-07-08_17-36.png
Then finally the IMV /QCV showed up sticking - this did not actually stall the engine but it was enough to show that it was the issue.
2023-07-08_17-39.png

MercTech20
Newbie
Posts: 7
Joined: Sat May 13, 2023 6:20 am

Re: Stuck Quantity Control Valve

Post by MercTech20 »

Initially this vehicle wouldnt start and when I first scoped out the Valve it was a very smooth waveform. This was when it was stuck. After reinstalling it, the vehicle started back up. But the waveform is not smooth at all.

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