Have 95 Series Fass that was installed about a year and a half ago and less than 15k miles on it. Has always worked well, gave good pressure and flow. SUddenly it has lost some pressure and pulses fuel. I have pulled the lines off at the injection pump and the return line off the fass to find that when it is running the fuel is "pulsing". Pressure and volume run normal then drop continuously. Voltage to the pump is constant. ONly thing noticeably different is that the pump sounds different and noise and flow coincide with eachother. Is the motor bad, the pump bad, or the whole setup? Also effects how the truck runs. Truck will run normal then suddenly miss like it has no fuel (surge die however you want say) when on the road. At idle it is stable. Any ideas out there?

 

have you changed the filters yet? after that I'd suspect a regulator issue, I have no first hand experience with fass, some others may chime in who do

 

yep, did a filter change. Once they filled up all the way it started pulsing again.