Thank you very much. This is an excellent video for anyone who who owns a MBE4000 mercedes. After doing the procedure, I had to start using either while releasing the air a few times. After getting running and getting final air out of the lines it's running great now. Thank so much!
Thank you I just modified my check valve fittings. I found that the one on the fuel cooler was doing the same exact thing… I have spoke to a Mercedes technician about it. He says this is a genetic aftermarket flaw by Detroit. When Mercedes was bought out. Detroit has been trying to piece it together so the old check valves were longer on the fittings. The ones you buy today are aftermarket and are not quite to spec causing this issue. With a strong fuel pump and the truck run daily it does not show too much problem. However once it gets age on it and sits more more than 48 hours without running it slowly loses prime. Like me only using my truck once, twice a week usually it has to damn near prime the system every time
You have another problem. That is there so that fuel won’t drain out when you remove that fitting. Now that you modified you will have no return to fuel tank.
No, the return works great. On both the inlet and the return lines, the one-way valve opens with fuel pressure. So as the engine draws fuel in the spring on the inlet collapses, allowing fuel to enter. Then, on the return, the valves open as the pressure rises. If I turned the valves around, then yes, you would be correct. Before the modification, both one-way valves were constantly open, causing loss of prime. The spring does not hold much pressure. You can blow on the inlet side of the one-way valve, and it will open. I'd say it will open with 5 psi, maybe less. Its purpose is just to close, so prime is not lost. I did double-check the return to make sure I had fuel after my modification. I went from 10 psi of pressure to 45 psi of pressure after the modification, and it's still running great.
I agree that there is a problem elsewhere. The valve on the return is simply to hold the fuel in the filter housing so you don't empty it if the line is disconnected. The inlet check valve holds fuel in the supply line. If you're losing prime after shutdown, then you have a leak on the suction side from the tank or you have internal leaks at the injectors.
Then what else could it be. They are fuel return check valves. Besides I have found engineers have never been for the mechanic. Why would they put a check valve there for the mechanic now??
I will agree it's not the best fuel system set up I've seen, but what I did has fixed the problem. It's on a feed truck and has to start 5-6 times a day. It would lose prime after an hour of sitting. It's used as my spare, so it may sit around not starting for 2 weeks, maybe more. Evertime I go to start it now it fires right up no problem.
