Mr Bee

Last Thursday I believe that my in tank pump quit. I had very little power and although the truck would run, I was unable to make any black smoke. I sumised that it was a fueling issue. At one point I floored it and threw a "Low Boost code". I did not have enough fuel to smoke, so it would not make boost either. I let it sit for 2 hours, cleared the code and it ran like it always has. Plenty of power and smoke if I put my foot in it. I thought the in tank fuel pump was taking a powder on me (145,000 miles) so I decided to install the FASS systen I had on the bench for the past two years. After install the truck would run fine as long as there was a need for fuel, but on letting off of the pedal and either coasting down hill, or coasting to a stop the fuel pressure would slowly drop to 3 PSI and the motor would shut off once it had drained the line. It was almost like once it went into bypass mode the valve would stick open and then once all fuel pressure was gone it would close and it would build pressure again. This scenerio was predictable and repeatable. This is a low pressure issue, not a high common rail pressure issue.
Things I did check to resolve...
1. Fuel level... 10 gallons was added, no difference, later 40 gallons was added and same issue... no difference.
2. The spring/ball valve adjacent to where the fuel hooks to the pump. Changed to 3 different ones... No change
3. Voltage to the FASS is consistant
4. Neither the fuel pump or the FASS had any abnormal heat.
I did take a pair of locking pliers and clamped the return line on the FASS and the issue was resolved, but the pump started to squeal a little, but it does not stall. (Had removed the temporary fuel gauge so I could not check pressure)

Is it possible the bypass valve in the fass is sticking? Has anyone had this issue before?
Is there another bypass valve in the bosch fuel pump other than the one adjacent to where the in line attaches?
Is there any other bypass valves I have not mentioned?
Need truck as it is a daily driver any help is appreciated
Thank you in advance
Brian

Mr Bee

Problem resolved... Took apart the relief valve in the FASS pump and there was gunk binding the ball causing the issue