Having trouble with fuel system Pac Car Mx 13 engine (2024)

Having air getting my system somehow in my paccar MX 13 engine. I replaced all fuel filters and I also replace two fuel lines in the passenger side plus the t fittings in the center of the frame there were two that I replaced if I let my truck sit I lose my prime and my engine I don't know what the problem could be the I don't think it's fuel pump or sensor I shut off passager side fuel tank and can run on left my prime stays. I shut off both sides and when it runs dry I turn open the passenger side I can hear the fuel pressure releasing into the system. I'm so baffled can anyone give me some tips on what it might be?

Also once I get the truck started my truck can stay on I don't lose my prime it only happens when I shut it off

Check valve stuck open

I will look into that but also it seems like the right passenger vent tube drips a little bit of fuel in my fuel is not leveling off evenly I'm getting more fuel sucked out of the driver side versus the passenger side the driver side it's not dripping would that effect the leveling of the fuel do you think I would need to replace my vent tube that's on top of the fuel tank

check out this video. sounds like it might be a similar symptom:

What year is this paccar do you stick the primary filter in from the top or from the bottom if from the bottom the way the return is routed if compression is comming up around the injectors it will push all off your fuel in your primary filter back to the tank when you shut it off you would have to put new injector crush washers and orings this effects the epa13 models if it comes in from the top I have seen the fuel heater break and start breaking down the middle of the sensor and not leak fuel but it’s small enough to suck air are you getting any bubbles in your primary filter

I am having the same problem we have replaced the o-rings in the lines between the fuel filters and the bleeder valve. we replaced the valve between the tanks. We replaced the fuel filters, pulled the check valve ball in the filter housing. We replaced the entire fuel water separator housing and still the same problem. I am going to check the pressure relief valve next and probably put new fuel lines on between the filters (2 week lead time on those). Ours is not all the time, it does it randomly. One time it will start fine, the next time it won't. Someone out there, a tech perhaps who has experience with Paccar or an engineer with Paccar, surely knows what could be causing the problem?????????? Please help!

Update on our situation, we cleaned the tank vents and the equalizing valve between the tanks. Then we left the pressure release valve on the end of the common fuel rail unplugged and started the truck. We of course got the stop engine light, but then we plugged it back in and started it again. After this we left it unplugged over night and in the morning we plugged it back in and cleared the codes once more and the truck has been fine ever since.........(knock on wood). So maybe it was a combination of the two that did the trick or one or the other by itself??????? The pressure release valve on the common fuel rail has a fuel return line on it that leads back into the fuel filter return side, so we wondered if we weren't having a problem with that valve sticking from time to time and allowing the system to bleed completely off? Either way the truck has gone to Phoenix and is on its way back now with no problems and no check engine lights!

What year truck do you have?