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Hello, I have a problem with my w211 220 CDI Mercedes. After the start of the engine y74 valve on the rail controls the fuel and a few seconds after engine starts the control is moved to y94. After the control is moved to y94, rail pressure go high and engire starts working roughly. I tried to change the y94 valve, but without effect. The ECU wont controls y94 fuel quantity valve. The ECU sends permanent square signal to it and wont change it. The y74 rail pressure valve is controlled normaly, the ECU changes duty cycle of the signal.
I tried to changed quantity valve and rail pressure valve with new ones. After that I changed injectors, input calibration data to the ECU, but still got a high pressure. I bought a second hand ECU and not change with it, still high pressure .
I tried to changed quantity valve and rail pressure valve with new ones. After that I changed injectors, input calibration data to the ECU, but still got a high pressure. I bought a second hand ECU and not change with it, still high pressure .
Recap: you've replaced both quantity valve and pressure valve and pressure still remains abnormally way too high. ECU + Injectors also replaced. All without significant improvement.
You have observed the ECU not changing control of Quantity valve but normally ramping command of Pressure valve... That control does sound normally working.
> How is the pressure measured and regulated..?
> Can you observe the live pressure value change between engine off vs. running?
>Is there a filter problem on low-pressure pump side ? (Could this be the ECU trying to compensate for low pressure feed)
It'll interesting to get this pressure control enigma figured out.
Last edited by CaliBenzDriver; 04-22-2022 at 03:38 PM.
Recap: you've replaced both quantity valve and pressure valve and pressure still remains abnormally way too high. ECU + Injectors also replaced. All without significant improvement.
You have observed the ECU not changing control of Quantity valve but normally ramping command of Pressure valve... That control does sound normally working.
> How is the pressure measured and regulated..?
> Can you observe the live pressure value change between engine off vs. running?
>Is there a filter problem on low-pressure pump side ? (Could this be the ECU trying to compensate for low pressure feed)
It'll interesting to get this pressure control enigma figured out.
The pressure is measured by pressure sensor on the rail, which seems working normally, because 10 or 15 second after the engine starts pressure is regulated by rail pressure sensor and the pressure is in the required range.
I think that if there is filter problem, the engine will starts hard.
I'm new here, writing from Northern Italy.
Just wondering if this problem got solved? I've also a problem with high rail pressure (and a noise) and I'm to find solutions.
I'm new here, writing from Northern Italy.
Just wondering if this problem got solved? I've also a problem with high rail pressure (and a noise) and I'm to find solutions.
Thanks,
Peter
Just changed the quantity valve y94 no luck . Engine light on after hitting 3k rpm and cracking noise from engine . Any update ?
Hello, in may case all the injection system (high pressure pump and injectors) has been controlled and seems ok.
My mechanic thinks that the noise comes from the chain.
Ciao,
Peter
Hello, in may case all the injection system (high pressure pump and injectors) has been controlled and seems ok.
My mechanic thinks that the noise comes from the chain.
Ciao,
Peter
Hello just an recenly update. i cleaned the EGR . Now i dont get high pressure anymore. But the strange thing is that from High went to Low pressure comon rail. I dont think that the noise comes from chain , Because no Engine light no noise . ENGINE LIGHT ON( noise comes)
Hello just an recenly update. i cleaned the EGR . Now i dont get high pressure anymore. But the strange thing is that from High went to Low pressure comon rail. I dont think that the noise comes from chain , Because no Engine light no noise . ENGINE LIGHT ON( noise comes)
UPDATE. (COMRAIL PRESSURE SOLVED) in my case the injector failed the back lesk test. I ended up rebuilding all 4 injectiors. 220 euro each . Changed even electric cable of injectors . Total cost 1000 euro.
04-05-2022, 05:40 AM
