CM2350 Code 4727

[Dieseltechjon]

(06-08-2026 )Rawze Wrote:  

(06-08-2026 )Dieseltechjon Wrote:  I have a truck right now that is doing the same thing. Repeated 4727 and I can see that the rail pressure does not drop on decel. There is no pressure in the return system and there is no air at all. I have pulled the actuator housing off the back of the block and made sure the orifice vent is not plugged or damaged. Wondering if anybody has experimented with drilling out that vent just a shade bigger. I was advised to replace it even though there are no apparent defects.

do proper injector leak tests on it...
info: https://rawze.com/forums/showthread.php?...3#pid75483

I ended up installing a new actuator and metering plate on the back of the hpfp but we are having the same issue. Rawz when performing the injector leakage test it looks like it's okay. I can go from 29k to about 7k in sixty seconds. I pulled the head off the pump to have a look but there is nothing obvious going on with it. It was swapped with another pump somewhere down the line so it's possible its incorrect, but I'll have to do some digging to figure that out.

[marek4792]

Fuel rail leak-down rate isn't supposed to be more 4,000 psi in a minute... Ideally you don't want to see a greater drop than 2,000 psi in a minute.. Assuming you replaced the pressure relief valve first... Re-tighten your injector tubes and all your fuel lines and repeat, if it persists start capping the fuel lines until you find the offending cylinder(s)..

[Rawze]

(06-24-2026 )Dieseltechjon Wrote:  ... I can go from 29k to about 7k in sixty seconds.
/...

That is quite a bad leak there. Starting at 29k,... It should still be above 25k after 60 seconds.

read meriks post above.