Common rail Fuel Pressure Too Low (ECR235EL & EC300E)

[grilli]

Hi,

We have two machines at our rental company that have been acting up lately.

I'll start with the Volvo ECR235EL. Coworker has replaced all injectors and liners + the electrical part of the FCV Valve about 300 hours ago + high pressure pumps. Problem is that the Common rail Fuel pressure is at max load and rpm's only about 120 000kpa. You can load the engine fully only about 5-10 seconds and it instantly reduces power and throws the warning Light. Codes are:

Fuel pressure regulator exceeding learning Limits - Too high
Closed loop Fuel pressure too low.

I noticed that the water seperator filter was suprisingly empty when I changed it. I usually plug the line that feeds Fuel to the filter but now no Fuel came from it thus tank being full. I pressurized tank with air and Fuel started coming from the pipe.

I have replaced Prv and pressure sensor but no luck.

By reading this forum I am going to drain a little Fuel from the bottom of the tank to a bottle and observate it after it sitting a while, also need to check the fuel pump wether it has loose bolts etc. Also going to try to drain the whole tank as we have good pump for it and fill some clean Fuel.

On to the second machine which has been a pain in the ass.

Same engine code but this time I have replaced everything. OEM Water seperator, whole FCV Valve, injectors, pressure sensor and high pressure pumps. Replacing the high pressure pumps fixed the original issue which was that the rail pressure was under 100 000kpa at max load. Now the pressure sits nicely at 180 000 and follows the Target pretty closely. This machine does not reduce power but only gives the code which states that the regulator is trying to compensate the pressure positively.

With the 235 we still have some fault tracing to do but with this 300 I am pretty lost. One thing I noticed while monitoring sensor values is that the code appears every time FCV Current drops below 1A. And it drops after the engine is hot and I have max load and rpm's on.

I appreciate all the responses.

 

[funwithfuel]

I have had issue with the fuel water separator. If you unbolt it, in the back there's a large plastic Alan plug. Make sure it's tight after you remove and inspect for trash up in the check balls seat. Verify you have no air intrusion at the bowl. You can do this by pressurizing the tank up to maybe ¾ bar or less. Just make sure to pinch or cap/plug the return to tank. Any negative pressure leak allowing air will weep fuel. Just don't get carried away. The lift pump is awfully strong, as long as your maintaining 5-6 bar at full throttle, I would think it's OK. How many hours?
So back to high fuel pressure with all these new parts. Have you removed and inspected the PWM on top of the FCV? If your machine is trying to throttle back the fuel flow, it's looking like a mechanical issue. So starting at the lift pump, it travels through final fuel filter before hitting the FCV. The FCV does 3 jobs. Maintain low side fuel pressure and provide an anti-drainback feature, this is done at the base. On top is the PWM, with no mA it's wide open feeding 6 bar to those high pressure pumps which jack it up to 7 or 800 bar. The higher the mA the lower the fuel pressure. It seems like either the PWM valve is stuck open or the o-rings on the stem might be damaged. Let's start there. Inspect the stem carefully. If there's the slightest hint of rust, change it, it's compromised. Good luck

 

[grilli]

Thanks for the answer. I will get back you asap. Great tips. The EC300 has 13k hours and 235 has 8k

 

[grilli]

Had some time to play around with the 235.

I took some Fuel from the drain plug to a clean bottle and it is looking fine at least for now. Have to monitor it still tho.

The water seperator ball was fine and no debris there. I cleaned it still but no luck.

In tech Tool cylinder compression test shows over 80% in all cylinders. Fuel system test fails and tells that the PVR is not reliable (it is new)

 

[funwithfuel]

Compression test is more of a comparison. It monitors crank speed and cam speed. The strongest or slowest hole is 100% That becomes the benchmark for the others.
You said only the pwm of the FCV was replaced, 300 hours ago. This fuel system has no tolerance for any water. The slightest bit will cause havoc throughout.
I wouldn't concern myself with the PRV yet. Only when you can't hit rail pressure target. You're exceeding, so it's not a concern yet. They have a limited lifetime though. Total open time of 200 seconds I believe is when they are deemed "unreliable" Once we get rail under control, then we can worry about stability. What did the PWM look like? Did you find any leaks on the low pressure side?

 

[grilli]

I am now working with the 235 which does not hit correct rail pressures. Target is somewhere around 135 000kpa and pressure is around 130 000kpa. IIRC the pressure should be around 150 000kpa at full throttle and load.

I have to get this machine to work before I can get my hands around the EC300 because that still works and pressures are good.

I was wrong, the whole Fcv Valve including the Pwm was changed.

 

[funwithfuel]

You're going to want to separate and monitor fuel return for that one. 9 times outta 10, it's one or more injectors with excessive return. There's a recommended test of electrically disconnecting the solenoid. The theory is, it only spills when the injector de-energizes. The reality is, you have to remove and cap the line from the rail to the connector tube for a reliable/ repeatable test result. Hope this helps

 

[grilli]

Do you have instructions for that one?