SCV (Suction Control Valve)

[Retz]

When I opened this thread I thought this was referring to Innova. Ibang vehicle experiencing SCV problem pala itong thread.

[arsen]

Kaya common problem sa SCV ay nag stuck open or partially open kaya nagkakaroon ng low fuel pressure, kaya loss of power at nagkakaroon ng erratic RPM at 2000 RPM.

Stuck open SCV means more volume of fuel is allowed to pass to be pushed by the pump to the commonrail kaya very high pressure sa rail. You can feel the power for a while parang naka chip but since meron pressure limiter sa rail na isang mechanical relief valve biglang magbabawas ng pressure sa common rail once excessively high na. as in biglaan let say from the value of 200MPa down to 25MPa. It takes sometime din to build enough pressue again lalo pa at biglang drop din ng engine RPM due to sudden loss of pressure.

Kung naka wide open throttle, dapat nasa max operating pressure na 180MPa. So what would you expect sa 25MPa kung ang kailangan ng WOT is 180? Di ba sudden loss of power.

Kung paulit-ulit ang cycle na high pressure-biglang low dahil nagrelief - at magbibuild-up ulet hanggang ma reach na naman ang excessively high pressure na makakapagpaOpen sa pressure limiter. nagiging erratic si engine.

[arsen]

Mali yata understanding mo, ang fail safe position ng SCV ay OPEN. Meaning kapag walang power ang actuator ay open ang SCV. When SCV is open the pressure at the suction of the high pressure pump is low because SCV is open back to the tank and effectively mababa ang rail pressure. So at full throttle SCV is almost closed to deliver higher suction pressure to the high pressure pump and then discharging the highest rail pressure possible.

No such thing as failsafe sa SCV. You can expect a behaviour once it fail depending sa type nya kung NO or NC. but SCV itself has no failsafe function.

What I am saying is. Normally Open SCV is not prone to stalling. Magiging erratic ang engine pero Hindi basta basta mamamatay ang makina sakaling magmalfunction ang SCV.

Unlike sa Normally Closed na kung mag stuck. hinde kakayaning itulak ng electromagnet ang spring para bumukas ang valve. Dahil Sarado si SCV wala ng flow ng fuel kaya tigok si engine. Biglang stall kung tawagin.

[jmtyper]

Problem pa rin pa ba ito sa mga 2012 Monteros? Has anyone experienced the SCV issue lately? How often ba ang recommended ng casa to replace the fuel filter and egr cleaned? Will this help to prolong the life or avoid SCV malfunction aside from gasing up from EuroIII and EuroIV compliant gas stations?

[babynos01]

Sirs goodmorning. Just for clarification lang.

SCV problem po ba yung kapag nasa high rev ka (around 2700 rom), parang may pumipigil sa makina na umarangkada?
Yung tataas rev mo, pero hesitate mag accelerate. Hindi mo naman inalis yung foot mo sa accelerator.
Kumakadyot kadyot yung engine kapag nag aacelerate ka ng 3/4 to full throttle.
Kapag city driving naman, hindi nakadyot kapag nag accelerate ka.

Our ride is a 2009 montero sport with 41k ODO.
If possible sirs, saan po ba ito located? Baka pwede ko i-check.

[zix888]

Sirs goodmorning. Just for clarification lang.

SCV problem po ba yung kapag nasa high rev ka (around 2700 rom), parang may pumipigil sa makina na umarangkada?
Yung tataas rev mo, pero hesitate mag accelerate. Hindi mo naman inalis yung foot mo sa accelerator.
Kumakadyot kadyot yung engine kapag nag aacelerate ka ng 3/4 to full throttle.
Kapag city driving naman, hindi nakadyot kapag nag accelerate ka.

Our ride is a 2009 montero sport with 41k ODO.
If possible sirs, saan po ba ito located? Baka pwede ko i-check.

if you are in front, looking at the opening between the engine and the battery, you can see the scv






cleaning pwede diy. pero replacing it needs a supply pump correction learning. (under the laptop)

[babynos01]

Thank you Sir zix. Hindi ko alam kung SCV problem na e.
Before kasi, nangyari din sa akin ito. And i found out na contaminated by water yung Diesel na nailagay sa may Cavite.
Sana ganon lang uli.

[Pidok]

Stuck open SCV means more volume of fuel is allowed to pass to be pushed by the pump to the commonrail kaya very high pressure sa rail. You can feel the power for a while parang naka chip but since meron pressure limiter sa rail na isang mechanical relief valve biglang magbabawas ng pressure sa common rail once excessively high na. as in biglaan let say from the value of 200MPa down to 25MPa. It takes sometime din to build enough pressue again lalo pa at biglang drop din ng engine RPM due to sudden loss of pressure.

Kung naka wide open throttle, dapat nasa max operating pressure na 180MPa. So what would you expect sa 25MPa kung ang kailangan ng WOT is 180? Di ba sudden loss of power.

Kung paulit-ulit ang cycle na high pressure-biglang low dahil nagrelief - at magbibuild-up ulet hanggang ma reach na naman ang excessively high pressure na makakapagpaOpen sa pressure limiter. nagiging erratic si engine.

Depende sa design ng common rail system, may SCV na parang dumping valve ang function. Open to the tank not to the suction of the pump.

[Pidok]

No such thing as failsafe sa SCV. You can expect a behaviour once it fail depending sa type nya kung NO or NC. but SCV itself has no failsafe function.

What I am saying is. Normally Open SCV is not prone to stalling. Magiging erratic ang engine pero Hindi basta basta mamamatay ang makina sakaling magmalfunction ang SCV.

Unlike sa Normally Closed na kung mag stuck. hinde kakayaning itulak ng electromagnet ang spring para bumukas ang valve. Dahil Sarado si SCV wala ng flow ng fuel kaya tigok si engine. Biglang stall kung tawagin.

For your info, sa design may fail safe postion ang mga valves lagi. Kung nakakita ka ng P& ID (piping and instrumentation diagram) naka-indictate ang fail position nya, FC ( fail close) or FO(fail open) or FL(fail last) - kapag nag fail yung actuator whether solenoid fails, or pneumatically fails to the safest position by design. So kung by design yung SCV ay nakakabit sa suction ng HP pump as a dumping valve just like in Bosch design (to dump fuel back to the fuel tank) which is normally open when de-energized, that's the safe position. If won't increase on RPM when SCV stuck * open position and will lose rail pressure.
I understood your point, SCV can also be installed in series with the suction of the pump (not as a dumping valve). When OPEN is more flow, more pressure. So if this is the case, the SCV being NO is not the in the failsafe position. If solenoid fails or maybe valve stuck up mechanically , there's a tendency of high pressure. But of course there is a pressure safety valve to avoid over pressure.:-)

[arsen]

Depende sa design ng common rail system, may SCV na parang dumping valve ang function. Open to the tank not to the suction of the pump.

Yun naman pala eh so bat mo sasabihin sa post#79 mo na mali ang understanding ko in my post #78?

I replied to someone having problem with his Strada.
For your info Strada and MS uses Denso System na metering-in (throttling) ang function ng SCV.

Mali talaga na kontrahin mo ang understanding ko sa Denso with your understanding with the Bosch System na bleeding-off (yung sinasabi mo na parang dumping valve) ang function ng SCV.

This is Mitsubishi Cars Talk talking about Strada SCV using Denso System