Losing prime

[NDT888]

Hi there, I have a '99 Cummins CM570 Signature 565 that I'm having problems with. My fuel system was losing prime so I replaced the suction lines from the tank to the fuel housing on the engine. Also installed a Davco filter system on it at the same time. It was good for a while but after a while it started losing prime again but has plenty of fuel in the Davco filter. Like half full in the bowl. I replaced the injectors as it wasnt running good and after doing an injector test had a few of them that weren't holding and had bubbles coming back. Wondering if anyone has come across this issue and what did it take to fix it. Thanks!

[Rawze]

- Always run the overhead valve adjustment before doing an injector leak/bubble test because you will get leakage if the injector rockers are out of adjustment.


as far as loosing prime, maybe bad check valve at the electric fuel pump?. Perhaps sucking air somewhere?.

- I have seen where sometimes you have to pressurize the fuel tanks to 10 psi to find where it may be sucking air. CAUTION THOUGH!!!: NEVER TRY TO REMOVE THE FUEL CAPS WITH ANY PRESSURE ON THE FUEL TANKS AT ALL .. EVEN A LITTLE BIT ... AS IT CAN BREAK YOUR HAND(s) and put someone in the hospital!.

[NDT888]

The injectors were adjusted shortly before the test . Put on a new primer and pressure fuel pump as my fuel pressure was very unsteady. Fluctuated as much as 60 psi while running down the road. Seems like it's losing prime on the return side??