2019 MP7 Low Fuel Pressure Under Load

[Christian Wagner]

Howdy fellas, I’m typically just a reader on these forums but I’ve ran out of avenues to take. I have a 2019 MR with an MP7 engine. It has about 900 hours on it and 8,000 miles, “Lightweight” emissions equipment, and has ran like a champ up until about three weeks ago. Now, under load, In top gear between 1200-1400rpm it will stutter and run out of power accompanied by a puff of soot, if I let out of the throttle and ease back into it it will sometimes come out of it. If I don’t let out of the throttle it will continue to bog and throw a code for low common rail pressure. I have no way to monitor my common rail pressure. I have done all of the simple things such aschecking fuel lines, replacing fuel filters, checking tank, etc. I plan on trying the pressure regulator next. Any help or tips would be greatly appreciated, not sure where to go after that pressure regulator. Ask any questions you want as well. 

[Christian Wagner]

In the odd case that anyone comes by this with the same issue, it was a broken injector hold down on #6.

[Mackpro]

Glad you found the problem and posted the fix . Yours being a common rail engine a couple of things we see with ours are clogged fuel filter inlet and the EPRV on the fuel rail sticking . The bad thing about the first few years of common rail engines is that they deleted the fuel pressure sensor. You either had to hook up a mechanical guage and read it or do a regen and watch the AHI after treatment fuel pressure with the laptop. I believe the 2023 models are back to having the fuel pressure sensor back  on them . A bulletin just came out about adding the sensor to some year models. As far as low fuel pressure, remove the rear fuel filter and look on the bottom of the fuel filter housing and using a Phillips screw driver remove the orange flapper and spring and clean out the fuel inlet. Found lots with trash hanging out of the flapper valve . Mack/Volvo figured out that the common rail engines didn’t need the Electronic pressure regulator valve on the fuel rail and due to issues with them failing and causing low power complaints, they came out with a delete kit for the EPRV .  This has to be done at the dealership due to engine ecm programing . We had all our truck done and now more issues. 

[fjh]

On 4/2/2022 at 8:02 PM, Mackpro said:

Glad you found the problem and posted the fix . Yours being a common rail engine a couple of things we see with ours are clogged fuel filter inlet and the EPRV on the fuel rail sticking . The bad thing about the first few years of common rail engines is that they deleted the fuel pressure sensor. You either had to hook up a mechanical guage and read it or do a regen and watch the AHI after treatment fuel pressure with the laptop. I believe the 2023 models are back to having the fuel pressure sensor back  on them . A bulletin just came out about adding the sensor to some year models. As far as low fuel pressure, remove the rear fuel filter and look on the bottom of the fuel filter housing and using a Phillips screw driver remove the orange flapper and spring and clean out the fuel inlet. Found lots with trash hanging out of the flapper valve . Mack/Volvo figured out that the common rail engines didn’t need the Electronic pressure regulator valve on the fuel rail and due to issues with them failing and causing low power complaints, they came out with a delete kit for the EPRV .  This has to be done at the dealership due to engine ecm programing . We had all our truck done and now more issues. 

Unfortunately they chose the cheap way out again with this dollar store fuel system ! They likly would have solved their injector cup issues had they used a proper HPCR system Owell it sort of works! Its 50%  better than I expected!

[Mackpro]

Exactly, not a true common rail rail system but somewhat better than we had .