Where to add Fuel Pump or Primer Bulb - Yanmar 3TN****

[coachlarry]

Hey all
I have a Deere mower with a Yanmar 3tn** in it and its very finicky about air in the lines. The lift pump is completely buried in steel and hoses and might have an air leak. I used a hand transfer pump to bleed it from in front of the separator. It worked well, and the engine is starting smoothly at this time. I want to put a primer bulb or inline pump on this machine and am thinking about putting it after the separator just before the injection pump. it is a pretty short run, and can just handle a small pump or a primer bulb on right angles. Is this a good place for the pump or bulb or should it be in front of the separator?

 

[CADplans]

Here is a pic of my Yanmar/Deere,,, the pump is the silver thing that looks like a car fuel filter.

 

[leonz]

Have you emptied the tank to check for a plugged strainer screen?

You may also have a bad fuel line from the tank to the water separator
that may be collapsed and needs to be replaced. The indirect injection
pumps create a lot of negative pressure as they pump a lot of fuel most
of which is returned to the tank.

 

[coachlarry]

Thank you very much for your responses

I checked the lift pump per tech manual and only had 1 psi at the separator inlet. I also bled the lines per manual and had no luck.

The lift Pump lever feels loose and yielded no results when trying to bleed. I decided in my head that there is a diaphragm issue or possible hose fitting air leak at the pump. I decided to prime the injection pump by forcing fuel through the separator into the pump without loosing any nuts. After doing so, I turned over the engine pulling from a fresh auxiliary tank of diesel. Since the motor turned over Successfully, I reattached the stock fuel line to the separator inlet and opened the separator valve. The engine now fires on first try with no priming, and runs perfectly.
I expect that I did not "fix" anything and hence decided to add the pump or bulb expecting this to happen again.

I inspected the line from the tank and did not find any collapse, but couldn't get to every inch. I ruled out the tank sludge theory as well since I have been able to start without it issue.

CAD, are you bypassing a mechanical pump in your setup, and what electrical circuit are you tapped into? I am thinking now that since I was successful in front of the separator, I should perhaps attach pump on vertical line at left in to photograph. Thoughts appreciated.

 

[CADplans]

CAD, are you bypassing a mechanical pump in your setup, and what electrical circuit are you tapped into? I am thinking now that since I was successful in front of the separator, I should perhaps attach pump on vertical line at left in to photograph. Thoughts appreciated.

My Yanmar came that way,,,
the pump runs as soon as the key is turned on.

From what I have read,, my system uses excess fuel flow to cool the injection pump.

 

[coachlarry]

My Yanmar came that way,,,
the pump runs as soon as the key is turned on.

From what I have read,, my system uses excess fuel flow to cool the injection pump.

Oh, interesting. Do you happen to know the psi of your pump? I believe I have a similar one rated at 4-7 psi.

 

[CADplans]

Oh, interesting. Do you happen to know the psi of your pump? I believe I have a similar one rated at 4-7 psi.

Sorry,, I never looked into the tech specs,,,

 

[Dave M7040]

Hey all
I have a Deere mower with a Yanmar 3tn** in it and its very finicky about air in the lines. The lift pump is completely buried in steel and hoses and might have an air leak. I used a hand transfer pump to bleed it from in front of the separator. It worked well, and the engine is starting smoothly at this time. I want to put a primer bulb or inline pump on this machine and am thinking about putting it after the separator just before the injection pump. it is a pretty short run, and can just handle a small pump or a primer bulb on right angles. Is this a good place for the pump or bulb or should it be in front of the separator?

View attachment 502269

I have a complete John Deere WSM for a tractor with a 3TNE74JK1.

Is this as similar to your tractor as it sounds.

If so they are looking for a minimum fuel pressure of 4.3 psi.

Better to find and fix the problem and not just band aid it.

An example from another tractor which may have nothing to do with your problem.

The return line from the injectors discharged in to the fuel tank. Normally the rubber hose connected to a steel pipe so the returning fuel went to the bottom of the tank.
Over time, this return steel pipe would break off. The returning fuel went into the tank. There were no leaks, what is the big deal?
The tractor became hard to start. Air in the system. Bleed the air and all was good until the tractor was shut down for a day or more and then the air problem again.

The steel return pipe which discharged near the bottom of the tank kept air from getting into the fuel lines as it was always below the fuel level. As soon as the pipe broke off air was getting in to the fuel lines as the engine cooled down. Air would rise up into the filters and then sucked down to the injection pump.

If this WSM would help you pm me and I can find a way to make it available.
4100 Compact Utility Tractors


Dave M7040

 

[leonz]

Your fuel pump is also the hand primer spring lever to bleed it.
You most likely have a torn diaphram.

If they are anything like the Duetz diaphram pumps they are easy to change
out with four small metric bolts on the diahpram housing.

 

[coachlarry]

I have a complete John Deere WSM for a tractor with a 3TNE74JK1.

Is this as similar to your tractor as it sounds.

If so they are looking for a minimum fuel pressure of 4.3 psi.

Better to find and fix the problem and not just band aid it.

An example from another tractor which may have nothing to do with your problem.

The return line from the injectors discharged in to the fuel tank. Normally the rubber hose connected to a steel pipe so the returning fuel went to the bottom of the tank.
Over time, this return steel pipe would break off. The returning fuel went into the tank. There were no leaks, what is the big deal?
The tractor became hard to start. Air in the system. Bleed the air and all was good until the tractor was shut down for a day or more and then the air problem again.

The steel return pipe which discharged near the bottom of the tank kept air from getting into the fuel lines as it was always below the fuel level. As soon as the pipe broke off air was getting in to the fuel lines as the engine cooled down. Air would rise up into the filters and then sucked down to the injection pump.

If this WSM would help you pm me and I can find a way to make it available.
4100 Compact Utility Tractors


Dave M7040

Very interesting about the return pipe in the tank. Going to check that! I have the technical manual for the machine and engine. Thank you very much for offering your help.

If it turns out to be the diaphragm in the lift pump, would you still fix it? I am inclined to bypass it and go electric.

Gaturftech.com has some obscure manuals available.