NAPA fuel pump # 610-1051

[Monty]

Question for Ron( I tried to email you but it was returned). What is the purpose for leaving the bleed screw partially open and does the temperature of the new pump get hot. I read in your post that it creates a continuous bleed system, but what is the purpose. Will it not operate properly if left in the closed position?

[Ray & Sandy Erps]

I have some experience with larger diesel engines which have a fuel return system built in.  I assumed these baby diesels did the same thing and that the fuel bleed valve was just a short cut to let air out of the fuel injector pump.  Now my curiosity is peeked, so I'll have to take a look to see exactly how the system works.  I suppose by leaving the bleeder valve open, there will just be a little extra fuel returning to the tank over the amount that is already returning to the tank and the electric pump will just pump a little faster.  The downside is, that if you don't close the valve when changing the fuel filter, you may be introducing more air into the injector pump as a result.

[Ray & Sandy Erps]

Well, I had to go see for myself.  On my older boat ('89 M25XP) the bleeder valve hose ties in with the injector fuel return lines.  Typically, the injector pump has it's own mechanical pump that supplies more fuel to the injectors than they need, so there is a fuel return line that sends the excess fuel back to the tank.  Ron, in your example, I believe you will find a higher flow of fuel into a coffee can while the engine is running even with the bleeder valve closed.  I suspect that the mechanical fuel pump pressure is higher than the electric supply pump.  Leaving the bleeder valve open while the engine is running would likely result in some of the warm excess injector fuel going back into the injector pump rather than back to the tank.  Would that hurt anything?  I don't think so but Universal engine manual recommends closing the bleeder valve when you're done bleeding and I guess to be conservative, one should follow the manual.

[Stu Jackson]

Ron, etc.,

Is this the nut on the top of the injector pump or the knurled knob?

Stu

[Joe Grabmeier #1205]

Ron, et al

Now that we have reached the "knurled fuel bleed valve knob", does anyone know how best to get a replacement for the knob valve?  Mine has broken off at the stem of the knob and is unworkable

[Stu Jackson]

Joe

Try this link and look around their site.

Stu

http://www.marinedieseldirect.com/universal/200157/

[Stu Jackson]

Joe,

Ron's right.  I just didn't know if you or others are aware of that site for technical engine information.  I've kept it in my Favorites list under my Boating folder for years.  A good resource.

Stu