I was wondering if you discovered what was causing your crane to lose prime after 3 weeks on a new filter and what your solution was? The M11 in my dump truck is getting progressively worse losing prime even with a Baldwin filter that is supposed to not drain fuel back. I don't want to wear my starter out prematurely having to crank it for 20-25 seconds on a 2nd start. It bobbles but keeps running shutting the truck off for 5 or so minutes while I load it.
Don't know what was causing that particular problem, but in my experience- most of the time losing prime is a bad fuel line. The "fabric" type ones break down letting in air and thus you lose prime. Also check all the fittings especially around the fuel filter.
It does has fabric type fuel lines. Maybe they're original and it would be good to just replace them? The idiots where I took for an oil change and service after I bought it put a new filter on a hand primer... that wasn't even connected. It made a loop from 1 side to the other. I just took the whole thing off. Is your Liebherr crane keeping prime since the new engine? Just curious if there was anything you remembered doing so you wouldn't have to change filters every 3 weeks.
Our Dodge PU went through a similar problem. There was a small section of fuel line that came off the filter that was rotten and letting the air in after a couple of days. I couldn’t even see the offending bit. Changed them all and problem went away. Cam
I've read you can leak air and not leak diesel. Apparently baby powder on the fuel lines can detect tiny tiny leaks that soapy water can't. The fuel tanks are a little low but I don't think that's part of the problem. I'll look over the fuel lines good when I go out tomorrow.