Dear All, I was wondering if someone could give me an in-depth guide and parts required to fitting a non return valve into my Diesel fuel system. When I leave my car standing for a while I'm struggling to start it. Good battery, new glow plugs but just not firing up. I've heard it mentioned before about doing this mod. Many thanks.

Is the in tank pump good? If so you shouldn't need a NRV.

However, any commercially available NRV can be spliced into the line between the tank and the FIP, the closer to the FIP the better.

I have heard of it being done, but I have not done it to my diesel. I don't see the point if there is no need for it.
It seems to be done to get around wear in the in tank pump as Marshall8hp says.
For diesel to run back into the tank it must be letting air in surely? Check the fuel filter gaskets/unions as well as the FIP.
Are there any bubbles showing in the clear pipe to the FIP when it has been standing for a bit?

I did it it's easy it only takes 10 minutes tops. The NRV's have a flow arrow on the body, make sure the arrow points to the fuel filter (obvious but easy to miss). The big fat bulkhead fuel pipe that goes to the fuel filter head is the one to cut. Insert the NRV push the pipe back together. I use zip ties for security.
I did have a weak lift pump in the tank at the time and I've had 2 fail since I've owned the car.

I had difficulty starting mine and saw air bubbles in the clear line in engine bay I traced the problem down to a leaking g fuel injection pump letting air creep in when motor was parked for a night

Another sneaky fault is leaking and/or split leak off return pipes. Touch them and see if they are soapy/slidy with diesel. I found I had to change mine annually