I have determined that the return line coming from the high injection pump through the fuel filter housing appears to be clogged. Pressure is building up in the fuel filter housing to the point that the fuel filter cap is blowing off. I have removed the banjo fitting at the high pressure injection pump for the return line and plenty of fuel is getting through there as well as to the banjo bolt at the front end of the fuel filter housing front side (before it goes through the housing). I do not see the same fuel passing through the return line after the fuel filter housing. Does anyone know how to clean the return line that passes through the housing? By the way, I have checked the return line past the housing back to the tank and it seems to be unobstructed. Is it possible to clean the return line through the housing without taking the whole housing off?

 

Is there a check valve on the return line that might be bad?
Or could the cascade overflow valve somehow be involved?

 

There are 3 fuel return lines on the common rail Cummins.
1 from the CP3, 1 from the back of the cylinder head & one from the pressure release valve.
They all combine in a passage at the fuel filter housing but have nothing to do with the fuel filter.
The passage routes to a single return line back to the fuel cannister on top of the fuel tank.
There is no check valve in the return line.

It is possible for blockage in any of the return lines but I don't think that would blow off the fuel filter housing cap.

If your fuel filter housing cap is blowing off, it's likely from too high fuel pressure from your FASS fuel pump.
Have you check your low side fuel pressure?

 

Got this issue fixed, but not sure exactly how
Cleaned out all return lines and pulled the COV
FASS pressure reads 17 psi
Best guess is something plugged the return line or the COV was stuck
Either way all is good so now I can head to the high country and chase elk around for archery season

 

Glad you got the problem resolved.

Just an FYI, Geno's Garage sells a really nice machined & polished steel fuel filter cannister screw on cap to replace the lame plastic cap.


http://www.genosgarage.com/FUEL-FILT...info/LT_FFCPP/