PChouinard

A bad seal washer on a banjo could be your problem. The smallest of holes will let air in with the engine off but may not let fuel out. You have a different set-up than I do but I had a bad o-ring around my fuel heater and it never even wept. I was cracking injectors every morning and wearing au de diesel #2 to work for cologne. Luck I'm an aircraft mechanic and typically smell like jp-8, mil-5606 or pd-680 anyhow.
Not long after that, the check valve started acting up and it took me a while to find that leak. The symptoms were the same though. The longer it sat, the harder it started..

totalloser

Excessive pressure will cause this as well. I joined this forum specifically to share this information with another member here fooling with dual lift pumps but haven't found the post yet. I had been having this problem with my dual Carters, and put a relay in to kill the framerail pump on startup using a control wire from the starter. Turn your pressure down, and it will go away. FASS are adjustable and run pretty high. Some are like 16 psi out of the box, and will cause this problem. My setup took my pressure down from 15 to 7 at startup. No more problems.

The high pressure locks the diaphragm in the vp44 to one side. I think this prevents flow, but I am not sure exactly what is happening as I have never had a pump apart. Either way, the high pressure is no good for startup. Unplug the FASS after it primes and your engine will start right up. Don't run this way or the diaphragm will tear and cost you a cool grand. But it will clearly demonstrate the problem.

Tray

Okay, there is no possible way that the FASS is causing my issues considering I had the FASS put on hoping to fix the problem in the first post. (Said in the first sentence of my orig post). Too much pressure will cause hard starts on dying VP44's. Mine is new. It starts perfectly once everything is primed again, I'm just losing prime somewhere. My guess is an o-ring from the injector replacement.

I know you were trying to help, and I appreciate it. It's just that every time someone has a FASS and hard start issue, they immediately want to blame the FASS, apparently even if the problem was there before the fass was installed, and that bugs me. My FASS was 12psi out of the box, and after changing the spring and getting 18psi now, it actually starts a little easier, I figure it's priming faster. Who knows.

dozer12216

Replace hose from filter to IP with a clear vinyl hose. If you see bubbles in line, you have a pin hole in suction side. May not cause a fuel leak, just pulls air into line. Do not leave vinyl hose on, just for diagnois.
By the way. Return line banjo fitting does bleed pressure to zero when shut down. Leak in high pressure circuit will not cause loss of prime. Will miss and have fuel loss somewhere.

totalloser

Oops. Double posted.

Actually I am trying to help, yes. Because I had a remarkably similar problem, and this was what caused it. Have fun.