[05hocummins]

2012 3500. I've been noticing my rail pressure bounce like this, after I let off the throttle while driving normal around town. Just replaced the fca. Truck runs a lot better with the FCA, but rail pressure is still bouncing like this. Any ideas what could be causing this? Is it normal?

 

[6.7L_MegaCab]

It's not normal. I checked the rail pressure on my truck last night with the Black Maxx (monitor monitor only as of a couple of years ago). Definitely shouldn't bounce around like that.

If your truck is running good otherwise, I kind of wonder if could be interference. Do you have a separate scan tool that can monitor & output the sensor data?

I would first check that the wiring is good then isolate your box tuner as a culprit by checking the fuel pressure with another scan tool.

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[05hocummins]

After replacing the FCA, it significantly reduced the bouncing on the rail pressure. No it really only doesn't it ounce. It's not all the time either. I'll have to get a new picture

Unfortunately, I don't have a scan tool. Would be nice to see if it was commanding it to do that.

 

[6.7L_MegaCab]

When I checked what the fuel pressure was doing it was correlated with the amount of throttle input. When I wasn't giving it any throttle, it was mostly flat at 6K-7K psi when cruising. Even at coasting, it was flat at 6K. The curves were more like rolling hills when getting on and letting off the throttle

I'm not certain if any scan tool can directly look at the FCA, at least I don't recall seeing that on my AutoEnginuity scan tool, other than the combined outputs that may be controlled by it.


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