NomadDick

Thanks, John...I'll try that and report back the voltage while the pump is running. The first filter is a water separator, the second is the actual fuel filter.

Good call. I did. Voltage was 12.44 at the battery, and 12.34 at the pump connector (loss of only 0.10v), but that was with the connector disconnected and the pump not running. If the pump is pulling more amperage than it should, I don't think I have a meter that can check for that unfortunately. When I let the pump run and run while it was still connected to the fuel tank with 4.5-gal of fuel in it, the suction fitting had no fuel in it, which indicates to me that the pump cannot suck the fuel up and out of the tank. I kinda-sorta replicated this test with the 3/4" hose and the 5-gal fuel jug...it would pull up the fuel out of the can maybe 6"-12" up the transparent hose I was using, but wouldn't pull it all the way into the suction side of the manifold. I then loosened the fuel filter AND the supply fitting on the injection pump, the same way we do when priming the system, and it STILL wouldn't pull the fuel those last few inches into the manifold. :-(

EDITED for clarity @ 1:43pm MST. Here's an update so far... I removed the suction line that runs from the tank to the suction side of the FASS pump/filter manifold and it was dry...not a drop of fuel in it at all. So, I tapped the tank and it SOUNDED like there was fuel in it. Next, I blew air down the suction line into the tank, and could faintly hear bubbles, which PROBABLY means that the fuel pickup tube is intact. I then went under the tank where the FASS sump is, and removed the drain plug, and was able to funnel just shy of 5gal of fuel out of it...4.5gal or so, into a fuel jug. So, I've established that it was NOT out of fuel in the tank. Then, to test the pump, I removed the flare fitting elbow, and threaded in a barbed fitting on the suction side of the FASS manifold, and ran a 3/4" hose into the 5-gal jug of diesel. When I turned the key on, it wouldn't even create enough suction to pull the diesel up and out of the jug, with the fuel level in the jug only inches below the pump. I was getting some "bypass" from the return hose, dropping back into the fuel tank and then draining out, so I disconnected the return fitting and pulled the check ball spring and ball out, cleaned it, inspected it, and it looked fine. The fitting begins putting pressure on the ball as soon as I begin to thread it into the manifold, so I think that's OK? Seems right, anyway. So, I'm thinking I have a weak FASS pump. I only have maybe 50k-60k and maybe 6 years of age on this pump. It's supposed to be top-end componentry...why is this thing giving up the ghost on me already? Is this typical? Thanks so much, NomadDick

Hi all. I'm newish to the forum, and could sure use help. For years, my 12v would light right up as soon as I turned the key to the start position, with no hesitation. However, lately, it's been losing it's fuel prime, and getting air mixed in somehow, after it sits for a few days or more. I have a FASS pump, which is probably 4-6 years old now. Seems to work "normally", yet somehow I'm getting air introduced into the system, and have had to open the feed line to the injection pump to bleed it before it will start up again. It's freaking annoying, because when I need to depend on it to run a load of whatever around town, I have to futz around with bleeding the fuel system to get it started again. No bueno!! FASS offers a bunch of different options, but I believe this is the one I have: https://fassride.com/shop/product/shop-category/1994-1998-5-9l-12v-cummins/fass-tsd10180f140g-titanium-signature-series-diesel-fuel-system-180f-140gph45psi-dodge-cummins-5-9l-1994-1998/ My stock injection pump was rebuilt at the same time the FASS was installed, and probably has 50k on it now, I'm guessing? Questions for the group: 1) Do FASS pumps begin to go bad over time and exhibit these symptoms? 2) Are there common places where air can get introduced into the system over a few days/weeks, even without diesel noticeably leaking onto the driveway? Anything you guys could offer would be super-helpful. I need to run a load down today, but have to go through the bleeding process, again. :-( Thank you so much, NomadDick