FBGNO Posted June 23, 2023 Share Posted June 23, 2023 Is there a fuel pressure sensor on a 2020 Granite GR64F with 425 MP7, that senses low fuel pressure and causes the truck to loose all power. This problem has been present since new. The check engine light comes on and the truck looses all power. Mack changes the fuel filter, resets the computer and says fuel filter was clogged. The truck runs well for three weeks with new filter then starts all over gain. We clear the computer and reset and the truck runs well, for anywhere from one day to three weeks, repeatedly after reset, without changing the fuel filters. We run beautiful clean fuel, I know the filters are not restricted, ten other trucks and ten other machines, running off of the same fuel, never have a problem, or have a fuel filter changed, for any other reason except a regularly scheduled service interval. Could there be a defective sensor that senses a very light normal restriction and it sets off some kind of fuel shut down? Quote Link to comment Share on other sites More sharing options...
Mackpro Posted June 23, 2023 Share Posted June 23, 2023 Mack deleted the fuel supply pressure on the common rail engines starting in 2017. They added it back on in middle 2021. Has the EPRV delete been done by the dealership? Biggest problem we see is trash gets stuck in the orange flapper in the rear of the fuel filter stand. Pull off rear fuel filter and remove flapper and check for trash. I’ll add pics soon Quote Link to comment Share on other sites More sharing options...
Mackpro Posted June 23, 2023 Share Posted June 23, 2023 https://static.nhtsa.gov/odi/tsbs/2021/MC-10195317-0001.pdf this is a must on the common rail engines. Software update is required so it’s pretty much a dealership repair. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted June 23, 2023 Share Posted June 23, 2023 Here is one that I had already removed the orange flapper and it was plugged solid. One time I did have the screw that holds the flapper on break off in the filter housing so be careful. Might be possible to clean it out without removing the flapper 1 Quote Link to comment Share on other sites More sharing options...
FBGNO Posted July 7, 2023 Author Share Posted July 7, 2023 Mackpro, Thank you for the response, I've been busy and I never had a chance to get on the site to see if I had any replies. I remember doing the delete probably about a year ago, Mack sent me the part and we did it in house. I will have to check the flapper in the filter housing, as I don't think I've ever seen it. We drop the filter, clean the housing and install the new one. I will check that out. Thank You for your time and attention I appreciate it. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted July 8, 2023 Share Posted July 8, 2023 The software update has to be done when the the EPRV delete is done so I hope it was done as well. Also injectors can have issues bust usually log codes. Also camshaft lobes are known to slip on the cam tube and this causes low power with and without fault codes. 2 Quote Link to comment Share on other sites More sharing options...
fjh Posted July 10, 2023 Share Posted July 10, 2023 On 7/8/2023 at 2:59 PM, Mackpro said: The software update has to be done when the the EPRV delete is done so I hope it was done as well. Also injectors can have issues bust usually log codes. Also camshaft lobes are known to slip on the cam tube and this causes low power with and without fault codes. yup another smart move in the name of saving a few pounds! At least they could have keyed these, Nope! Quote Link to comment Share on other sites More sharing options...
FBGNO Posted July 11, 2023 Author Share Posted July 11, 2023 After I did the delete, Mack programed it. After putting more time into this, I'm starting to believe that it's something in the DEF department. Still working on it as It isn't a constant problem, it's more intermittent. Thank you all that have responded, it's appreciated. I'm an old dog in a new world, and I'm still feeling my way around all of this computer and electronics garbage. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted July 11, 2023 Share Posted July 11, 2023 If you can find out what the actual fault code number was let me know . We only have MP8’s here but had a couple of 2020 year model trucks just randomly loose power and set code for low fuel rail pressure or something to that effect. Ended up the dealership putting 6 new injectors in and it solved the problem. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted July 13, 2023 Share Posted July 13, 2023 If you are getting either of the codes I have circled, very possible camshaft lobe on one of the pumping injectors has slipped. We had 2 in one week throw these codes and the #4 injector cam lobe had slipped on both trucks. One was a 18 CXU with 600,000 miles and the other was a much newer Anthem with 300,000 miles. 1 Quote Link to comment Share on other sites More sharing options...
FBGNO Posted September 19, 2023 Author Share Posted September 19, 2023 Mack Pro, Thank you for responding, I'm sorry for the delayed response to you. I haven't been on since I last answered you, and I didn't know that you sent more correspondence. Please realize that I really do appreciate you taking the time to answer and help out with my problem. Here's what happened. I said that the truck has been doing this from new, it's been back to Mack at least 8 times for the problem, they kept telling me clogged filters, (bull$&%t). I started to think that it had something to do with the def system, so I asked the driver if the truck goes into regeneration often, he told me the truck only went into regen once since new. I thought that was strange. Last week he got back to the garag, at the end of the day, and while backing into the yard the truck started to regen, It went for 50 minutes, since that time the truck is running perfectly. Quote Link to comment Share on other sites More sharing options...
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