The Ballad Exchange

Haven't been out again, but there was some air in the fuel filter after the 5 hour run

I'm still really dumb about diesels, so humor me here.... Is it possible (or not?) to put your electric fuel pump on the other side of your CAV primary filter? Seems like negative pressure (suction) is the enemy of any fluid transfer system. Low static pressures reduce flow rates, and each O-ring, seal, valve, bleed screw etc. on the suction side is a candidate for admitting air. One reason many auto manufacturers put their stage1 electric fuel pump inside the actual tank.

A somewhat odd but maybe interesting approach would be a 'day tank' up under the coaming, filled by the main tank & gravity-feeding the engine like your previous boat. You'd want a reliable limit switch to prevent over-filling, or a return overflow tube. Could increase the meager tank volume of the Ballad by 3 gallons or so, too.

All good thoughts Bob. I agree, as soon as you start sucking fuel, air may creep in. By pushing it through the system any leaks will be outward, ie fuel leaks, and clearly visible.
The Facet pump instructions state that it should be located before the main fuel filter, and below the tank (not an option in the Ballad!) It also insists on a small strainer-type 74 micron filter threaded onto the fuel pump intake as a first line of defence (just another filter to get blocked and need changing?).
Still, probably my best bet is to re-route the fuel flow to be: tank/pump (with strainer filter)/main filter/engine filter/injector pump. That would make the whole system pressurized ... no vacuum anywhere.
Yup, I see that's what I need to do! Just ordered 4- 74 micron filters from Aircraft Spruce. Time to do some re-plumbing.

On the day tank, good idea too ... maybe later!

Thanks for your input, guys!

Did moving the fuel pump work for you, Peter?

Haven't done it yet Bob. Discovery of rotten main beams under our sun deck (12' up) derailed boat work for a while. All done now, and the visitors have gone, so now it's time to get back to the important stuff

Understand those realities. We spent yesterday pulling 7 - 8000lbs of batteries out of the basement & lowering 3000# pounds down into it. A blow to both the time & discretionary budgets.

Well, with the tank to fuel pump to engine setup we motored for 8 hours this weekend with nary so much as a bubble of air in the fuel filter, which is at the high point of the system. It comes off with a couple of bolts and I left the hoses a bit long so it can be flipped upside down to see if there is any air in the glass bowl. None None None, and no fuel leaks either... looks like this problem is solved, but only time will tell. I need to rebuild my trust in the machine! Even with 8 hours under power, we still got in some good sailing across Juan de Fuca Straight and back.

Just came back from 2 weeks out on the boat. We mostly sailed but the times we had to motor everything worked flawlessly. Pushing on the CAV filter primer bulb it always used to be a bit spongy (air). Now it's as hard as the proverbial rock ... all the time!
Colour me one happy camper

Yay! Sounds like you had one of those intermittent vacuum leaks that only shows up when the system is pulling hard negative pressure. Always a tough problem to track down, with any vehicle.