Fuel system issues Paccar mx13 air in fuel line

check any and all fuel lines for leaking, maybe a lose hold down nut, there should be tell tale signs of leaking fuel.

check any and all flex/rubber lines for cracks, loose clamps as well. check the fuel filter for leaks as well.

the fuel inlet line from the injector pump may have a loose line, there may be a leak there.

 

has the fuel filter been changed over?

 

wondering if it was not properly pre-filled before installing.

 

How long since last valve set?

 

I’ve had issues for over a year with my 2017 t880 pactar mx13. I’d fire it up and for no apparent reason it would shut off and my fuel prime would be gone. I’d have to prime the system with the priming pump for what seemed like for ever and still use ether to get it to fire up and it would run again sometimes for days other for hours. I changed the everything easy at first like filters and fuel line o rings and at first it seemed to help and then back to square one. I went ahead and changed the entire filter/primer assembly and it seemed to work, again it was temporary, but the priming definitely improved and was much better! I eventually removed and inspected all my fuel hoses and reinstalled them to make sure there were no obstructions in the lines causing air cavitation. I just replaced the water fuel separator after I was inspecting it and wondered if the by bass valve on the return line could be sticking open enough to cause fuel to return to the tanks instead of reaching the engine. I went ahead and replaced it with a new one and was surprised to see that the new one actually has a run/prime selector knob on the return side. That means paccar knew of this cavitation problem and added a fix to the new separator assembly. I was able to replicate the issue by moving the selector to the prime mode and it would start draining the filter like it had in the past and as soon as I’d close it the air would be gone! Good luck guys I sure miss the old technology!

 

I have an paccar Mx 13 that has a leak behind the fuel filter housing assembly could that be the problem with it not starting and it starts if u run it day after day but if it sits for a day it’s hard to start - any advise for tthat? Does it have a primer pump as well? Thx and good luck to all u guys with ur trucks thx