Fuel pressure readings

[tylerrmack]

2016 1500 6.2l. Having a intermittent rough idle stumble and even stumbles with increase to 1000k RPM. Its slight but noticeable. I have a cheap OBD2 bluetooth and Torque app for reading. I don't know how accurate it is, but figure all its doing is sending numbers, so should be find. With my truck idling fuel pressure is sporadic around 45psi with dips to 30 and even 22 psi, then sometimes up to 50psi. This seemed to be at about the same frequency as my stumble. The other reading if Fuel rail pressure which is much higher and cycles high and low but not as drastically. Is this normal? I tried attaching a screen shot. The numbers on the left are wrong but the graph shows the fluctuation. If someone knows the right reading to be expected or have a sensor to check their truck and see what the reading are, I would appreciate it.

[newdude]

Being so heavily computer controlled, I'd be willing to bet that it is normal. Mind you to, some of these handheld OBD devices and what not don't always have near the reading capabilities of the GM MDI and GDS2 system can show. If it were low enough or long enough, it would be setting low fuel pressure codes left and right.

 

 

Electronic Returnless Fuel System

The electronic returnless fuel system is a microprocessor controlled fuel delivery system which transports fuel from the tank to the fuel rail. It functions as an electronic replacement for a traditional, mechanical fuel pressure regulator. The pressure relief regulator valve within the fuel tank provides an added measure of over pressure protection. Desired fuel pressure is commanded by the engine control module (ECM), and transmitted to the fuel pump driver control module via a GMLAN serial data message. A fuel pressure sensor located on the fuel feed pipe provides the feedback the engine control module requires for Closed Loop fuel pressure control.

Fuel Pump Driver Control Module

The fuel pump driver control module is a serviceable GMLAN module. The fuel pump driver control module receives the desired fuel pressure message from the engine control module (ECM) and controls the fuel pump located within the fuel tank to achieve the desired fuel pressure. The fuel pump driver control module sends a 25 kHz PWM signal to the fuel pump, and pump speed is changed by varying the duty cycle of this signal. Maximum current supplied to the fuel pump is 22 A.

Fuel Pressure Sensor

The fuel pressure sensor is a serviceable 5 V, 3-pin device. It is located on the fuel feed line forward of the fuel tank, and receives power and ground from the engine control module through a vehicle wiring harness. The sensor provides a fuel pressure signal to the engine control module, which is used to provide Closed Loop fuel pressure control.

 

 

[tylerrmack]

Yeah i figure it would through codes if bad enough. I have had misfire code previously chalked up to faulty spark plug. Dont know if that was just BS. I figure these things have certain parameters that dont throw codes as long as its able to adjust. Just like it wont throw a misfire code unless its really bad multiple misfires. My question is that if its normal or is the system having to constantly adjust/compensate to stay just below the code throwing threshold?

[Shane_DeLo]

Can someone please help me I’m trying to replace the flex fuel composition sensor I pulled the fuel pump fuse and relay but I’m still holding pressure… please help me I have nothing but problems with this truck

 

[Cri5]

Did you ever get this figured out? My 2017 GMC Yukon is behaving almost identically and not normal in my experience. Any help would be appreciated.