[Richard]

A couple of things.

Before you take the coach apart, cobble together some fittings and use a 5 gallon can of diesel directly into the fuel filter. Or use the pressure sprayer. We may have crossed wires. When using the pressure sprayer, pump it up, and leave it attached until the engine runs. That way you fill the filter and line to the engine.

Getting under the coach will do NOTHING for you on the fuel line. Open the fuel bay door, and remove the shiny stainless vanity plate. All of the threaded bungs for the fuel lines are within reach. I was able to use a crow’s foot wrench to loosen the fuel line from the elbow where it goes into the tank.

If it were me, at the this point I am pulling that filter assembly and replacing with a Davco see so I can see what is going on with the fuel. https://www.jmesales.com/davco-fuel-pro-...h0QAvD_BwE. A few posts back you said you saw bubbles at the primer bulb when using the pressure sprayer. If bubbles coming out, bubbles going in. If that is true, that is where you are losing prime.