Thats roughly 10000 psi. Definitly too low for any decent acceleration.
However the corresponding voltage/pressure may not be exactly linear.
1500 bar is 21700 psi. I know mine will max out at around 26000 psi. Maybe your sensor is different?
This could mean a bad sensor, incorrect sensor calibration (wrong sensor?), or a short circuit somewhere.


The logic is all in the ECM. Exactly what that is I dont know.
Yeti does a lot of custom tuning. Maybe he will have more knowledge about this.

Its acting like its in limp mode. If thats the case some code should be set indicatiting a fuel system or boost problem.
Could also be a fuel supply problem.


Can you see fuel leaking?
Could be a bad solenoid, bad o-ring, or improper installation. But if there was a problem with fuel rail pressure and/or solenoid control, a code should be set.


What some of the cummins and duramax guys do is they replace the pressure relief valve with a solid plug. I've thought of doing this. But the ECM wants to see some voltage drop from the solenoid circuit. So you would have to insert a resistor into the circuit that is close to the resistance of the solenoid coil.
Might help with diagnosis but if the ECM realizes that it cant control rail pressure in its normal manner, it should set a code.

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- Ive put new sensor in. That was first replacement.




- The only codes are P0101, which is MAF sensor. I've put air thru the sensor , and it works perfect, i.e. on scan tool shows full range. It throus this code because turbo is not spinnin enough (not much fuel) so no boost. I have only 6 psi boost on MAP sensor. I was thinking map is bad, but put air compressor against it (the video is on u-tube, just type UNICAPRO) and it went all the way up to 25 psi. Also I;ve put pressure gauge prior HP pump. I.e. checked in-tank lift pump. Constant 45 psi. No leaks. there is also video on u-tube.




There is no physical fuel leak. By leak I ment the return via solenoid valve. I've replaced the solenoid valve also. So that's why I'm thinking the rail seal surface, where solenoid meets the rail, is bad there fore it leaks fuel.



Really? Totally blocking the return? But how then the rail pressure is bled back? I can raise totally up to max value. Or the FQS will limit the amount of fuel entering the HP pump? I'm looking to put some safety valve inline the rail output. Don't just want to slam shut the retursn.

Few diagnostics I'm going to try soon are:

- Put a scope onto fuel pressure solenoid. It is negative 12v PWM. So shoud see full pulse if ECU does not limit it electronically. If I see full wave pulse, then it is mechanical issue. If I dont see full control pulse, then it is software cutting the engine power.

- Then will build simple PWM controller, and feed it via pressure sensor. Trying by pass the ECU. And will control rail pressure myself, see if I can build up pressure inside the rail. I'll have to some how fool the ECU so it thinks it is controlling the pressure

im not familiar with your engine but i see youre getting 45psi fuel pressure from your lift pump, ours dont go over 15 psi, maybe that is too high of psi for your cp3 pump. or if ecu would accept that kind of pressure before puting the engine into limp mode.

The engine is VM Motori RA428. Italian make. 177HP 420nM torque (can be easily tuned to 250HP and 600nm torque), turbo charged, servo VGT controlled. Cast iron case, tough and powerfull engine.

The pressure range for intake is around 35-70psi. So mine is right in the middle. Also, there is no means of control of inlet pressure, i.e. no sensors telling the ECU that inlet is high. Only output control.

Thanks for ideas thou

also came to my mind i see you replaced a couple of injectors i assume you programmed calibration codes "trim codes" located on top of the injectors. the reason im saying this i heard some people with MB sprinters had issues with lowrail pressure due to incorrect calibration codes on injectors. this does not affect us much with the older vm 2.8 installed in north american market.

well, I must lean towards software issues now. As some more tests revelaed that it is not the rail. My old JK had few failures so the guy asked me to have a look. After finishing with him, I swapped the rails. I now for fact that JK's rail is perfect. But..no effect on JKU (my new one). So the rail issue is out of the question now.

I also hooked up the scope to rail pressure solenoid. It does respond to throttle, i.e. the pulse width gets wider, telling me that ECU controls it. But how much, i don't know. Will have to hook up the scope to proper running engine (probably will hook to JU after I'm totally finished with it)

one more of those unknown stop places...

One thing I mentioned earlier, want to touch base. One of the errors is Vehicle Configuration mismatch. The ECU is actually from dodge nitro 2.8 crd. But they share same engine thou...I'd guess rail pressure must be similar more or less..

Hi I had similar issues of low rail pressure at 11500psi should be about 22000 psi. I was getting white smoke under load and no power. I diagnosed a faulty injector ny using a stethascope and listening to the injectors 3 were ticking (thats good) 1 was actually ringing like a bell ( quite painful on the ear) I canged all 4 injectors as I snapped 2 trying to remove them. Anyway that cured the smoking but I was still down on power and it pinging into limp mode. Came up with barometric pressure bad correlation. I changed the MAF but no change. I changed the MAP sensor on the intake manifold and that cured it. Souns like like you may have a bad injector and posibbly bad acting MAF sensor too.
Regards
Jeff

FYI:
It is my best understanding that the MAF sensor signal is used strictly for the operation of the EGR system by the ECM and nothing else.
Disconnecting it will not affect other engine operating functions / parameters or cause "limp" mode operation.
That is why some simply unplug the MAF to limit EGR operation without affecting engine performance until a EGR delete kit or block off plate can be installed.
Unplugging it or totally removing it may set a P0101 DTC.

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