Hi, I rebuilt my roosa master fuel pump last year after the common rubber weight retainer failure. It went smoothly thanks to everyone's advice on this site. I added the solid weight retainer and it ran great for the season. It is now acting up. It starts and idles fine and I can increase the throttle for some time even wide open throttle, but eventually it jumps down to basically idle speed. It will stay there even holding the pedal fully or the throttle lever until I move it back to idle position. Then if I press the pedal again it will increase RPM for a short time and again go back to idle speed. It was similar to the symptoms of the return check valve getting gummed up with the rubber pieces. I took the check valve out of the equation and even running with the return line removed, it has the same issues. I checked inside of the top cover and it is still pristine. Fuel filters are pretty new and there is a full stream of clean fuel getting to the fuel pump. Does anyone have any ideas what else to check before I look to pull the fuel pump and tear into it or send it off? Thanks
It needs that check valve in there to create some internal pressure to work properly. Blow out that return line and make sure it's not clogged and goes back to tank freely. Hopefully thepumpguysc can get you sorted, or if you need, send it off to him. He did mine in 2017 and I've had 0 issues with her so far.
Check crankcase for high oil level from diesel fuel.
Thanks for the reply. I have tried it with and without the check valve, as with it being similar to the previous issue that seemed like a good starting point. Maybe I should throw in another check valve, though the current new one still looks clean inside. I have pulled the return line after the last injector and it was flowing well. It still stalled with that line pulled after a bit of time.
Thanks, you might be on to something. It does look to be high. Not sure the best way to tell if that is from diesel. I couldn't smell it. Would that be failed umbrella seals on that front shaft?
That or bad/leaky injector
I really don't think that I have diesel in the oil. I drained it and it just seems like used oil consistency wise and no smell. I filled it back up to full and might run it for a bit tomorrow to see if that level changes at all. I did order some dye that I may try in the fuel to see if it shows up in the oil or by the injectors. I'm just not sure how the machine would run fine at times and then drop throttle to a crawl.
Did you check for yuck in tank? "Pretty new" filters are no match for yuck. Could also be clogging fuel shut off petcock. Is fuel tank cap venting? Then there's that whole return line check valve thing.
Hi, yes I seem to have good fuel flow in the tube right before the fuel pump when I have pulled that line. I have also tried with the fuel cap off and with the return line (with and without the check valve) and same results.
Did you check the line from the last injector to the tank?
Yes I ran it with the line removed after the last injector. I have also removed all of the tubing between the injectors and cleaned and replaced seals.