Air Leak and Lift Pump, 2GMF

[phantomracer]

Originally Posted by svstrider

I have a squeeze bulb in fuel line after Primary racor filter on my Yanmar 3GM30's. This has worked well for bleeding the fuel lines to the secondary fuel filter. However I am wondering if I install a Facet electric fuel pump instead of the primer bulb will I be able to bleed fuel all the way to the injectors? I read that the electric fuel pump could also be used to run the engine if the Yanmar's fuel pump was to fail. What sort of problems would this create?

I have also found that the 3GM30 does not need the injectors cracked and bled even if the engine has run out of fuel. Is there any problem in not bleeding the fuel lines past the Yanmar high pressure fuel pump?
thanks for the advice.

That makes sense. If you run out of fuel, the lines from the injector pump should still be primed, you just don't have enough fuel to push fuel out of the injectors. Unless you break a high pressure line open (to replace an injector, or to ensure the motor wont start when adjusting valves etc), I would assume you wouldn't have to bleed it.

Having the electric left pump on our boat rocks. pumps right through the factory mechanical pump without a problem.

[phantomracer]

Originally Posted by satnav

Phantomracer, I think the issue is having a secondary fuel tank within or close to the engine compartment. My secondary tank is on a partial bulkhead between the engine and the transmission, below the galley sink. If indeed there were a fire in the engine compartment, the secondary tank could add to the problem.

I didn't think diesel burned unless it was atomized (or under pressure or wicked). i think in liquid form it would, most likely, put out the fire than make it worse.

I guess I don't see the connection with a secondary tank and an electric lift pump

Paul

[DeepFrz]

pumps right through the factory mechanical pump without a problem.

And it will keep doing that even if your mechanical lift pump diaphragm springs a leak. To the point of filling your crankcase with diesel, all while you are unaware that there is a problem, until...

[phantomracer]

Originally Posted by DeepFrz

And it will keep doing that even if your mechanical lift pump diaphragm springs a leak. To the point of filling your crankcase with diesel, all while you are unaware that there is a problem, until...

If you are worried, could aways put a switch inline an use it to start the motor only. could just bypass the mechanical pump as well

[DeepFrz]

If you are worried, could aways put a switch inline an use it to start the motor only. could just bypass the mechanical pump as well

Yes, those are both solutions. Better yet is to use the pump only to fill the filters after changing them by putting in a switch that only powers the pump while you hold the switch on.

[satnav]

Correct about liquid diesel not burning, though I think the hoses would melt first, allowing smaller amounts of diesel to "feed" the fire. The main purpose of the reserve tank is to provide some insurance to running out of fuel. I know I have about three hours of running time (3hmf) if the main tank were to run out. My engine is extremely easy to get to, I keep it spotless, check it all the time, and so a fire in the engine compartment seems remote.

[PaulM]

I did find the air leak. The fitting on the pick-up tube was cracked. All well now.

Back to the other part of my original post

If the lift pump is bad I would rather replace it with an electric pump. Is the there a recommended pump? Would I need a return line before the injection pump.
Paul[/QUOTE]

[osirissail]

Originally Posted by PaulM

. . . If the lift pump is bad I would rather replace it with an electric pump. Is the there a recommended pump? Would I need a return line before the injection pump.
Paul

[/QUOTE]

The beauty of diesel engines is that they do not need any electricity to operate. So if you put an electric lift pump on the engine versus the mechanical lift pump, then should you have an electrical failure - you will not have the use of the engine. That could be rather bad in a blow or harbor entry.
- - There is no problem with adding a Walbro electric pump in addition to the mechanical lift pump.

[satnav]

Keep in mind that if the fuel source is above the engine, where the fuel is gravity fed, then the fuel feed pump is not needed. Most systems don't have this design option but it is something to consider. I agree with Osirissail, installing an electric fuel pump on the engine defeats the purpose of an all mechanical engine.

[satnav]

PaulM, I would not replace the engines fuel feed pump with an electric unit but if you did, then I'd say to use a pump that is not over-capacity to the fuel system - too much fuel for the system to handle, injectors and return line.

[Chief Engineer]

The Yanmar fuel lift pump is not an expensive item.........PM me if you would like a spare

[never monday]

- - There is no problem with adding a Walbro electric pump in addition to the mechanical lift pump.

there is if the diaphragm of the mechanical pump is ruptured.

[osirissail]

Originally Posted by never monday

there is if the diaphragm of the mechanical pump is ruptured.

There is virtually no chance that will happen. Lift pumps have poppet (one way) valves that let the fuel into the diaphragm chamber and then another one way valve to pass the fuel on down line. Pass through fuel from an electric pump will have no effect on the operation of the mechanical lift pump.
- - The diaphragm in a mechanical lift pump will wear out, crack, get stiff and eventually stop pumping fuel. If it is split/cracked then pressurizing the fuel system will result in fuel dripping or draining from the mechanical lift pump casing. Which is very good to know as you can then rebuild the lift pump or bypass it with a piece of fuel hose and some hose clamps. The Walbro pump will supply fuel to the diesel engine and that will get you to a safe harbor where you can fix the thing properly.
- - I have two Walbro's in my fuel system, one for pressurizing the engine system downstream from the main Racor filters and can also be used to recirculate the diesel back to the main tank after passing through the main Racor filters (polishing). The other is at the main diesel tank and pressurizes the entire fuel system for leak checks and bleeding of the high pressure pump.

- - Mechanical lift pumps are left over from the car/truck old days when everything had to be mechanical. The newer engines use small electric pumps and save all the cams and levers, etc. involved in a mechanical pump. But still I would be sure to have a spare electrical fuel pump specific to that engine stored away in the bilge just like I keep a spare rebuild kit for my mechanical lift pump stored away.
- - Currently Walbro diesel pumps are the only rated (UL approved) diesel pumps for marine use. There may be others outside the USA but as of a few years ago - Walbro was "it" for the USA.