John deere 850 fuel pump - no output

[Chuck_L]

Good Day. Well I just joined up here. Having a problem with tractor I inherited dad; I hope I'm asking the question in the correct place. If not, please let me know.

Ok, the Tractor is a John Deere 850, late '80's. It has been running fine until few days ago when it started, ran for 20 sec, then died.

The fuel flows freely to the pump. But the pump itself just "spits" a little out of the three ports. The throttle linkage is fine. I removed the pump, did a little online research. I then dissasembled the pump. There is nothing in this mechanism that seems overly worn or suspect to the eye.

I am not experienced with diesel systems, but I am experienced with machinery in general. I am really quite flumoxed as to why this thing is not pumping out fuel. The pistons move freely. The check valves are pristine. The parts that make up the flow regulating mechanisms are, again, pristine. These three pistons are driven by cam lobes which are certainly still in the tractor and certainly still turning.

I don't see anything mechanically that says it shouldn't work. But it just stares at me, not working. So it's obviouly smarter than me.

Thanks in advance for any insight

Chuck

 

[beenthere]

Welcome to TBN
What "pump" are you talking about? The injection pump, or a different one?
Put up a pic or two and good help/advice should come your way.

 

[Chuck_L]

Thanks Beenthere, I'm uploading a couple of pics.
It is the fuel injection pump.

 

[beenthere]

From what little I know about injection pumps, you may have dived down that rabbit hole too quickly. But hope "thepumpguysc" member will chime back in, or you can seek his advice from other threads here, as to what to do next.
Hopefully the recovery is poassible, but I wouldn't count on it. Search for more injection pump information, and we will pray for you.

 

[thepumpguysc]

If u flip it over and go thru the bottom.. remove the pin, roller tappets.. PAY ATTENTION TO THE TIMING SHIMS UNDER EACH.!!
Then CAREFULLY lift out the pumping plungers..
Look at the “cut” (helix)..
If u see score marks, they’re bad..

 

[thepumpguysc]

When ur lifting up the plungers.. PAY ATTENTION TO WHICH WAY THE CUT FACES..

 

[Chuck_L]

Hello Pump guy. Well, I havent taken it apart from the back side. I removed "check valve" mechanisms from the front. I then took out the "cylinders" into which the "plungers" (I believe you are talking about) fit.

Yes, I became aware of the orientation of them as I was working with it. I was able to see (barely) that there is a kind of helical cut in them, and that was my "ah ha" moment where I understood how they regulate the flow.

Still, it sure seems odd that the tractor would run fine then suddenly not. I would think that if those plungers are suseptible to becoming worn, a person would notice having to throttle up the tractor more and more, as they wear and lose pressure.

Then again, maybe it just gets to a point where the presure is just no longer enough to get past the check valves... I guess I can see that happening in a more sudden fashion, so to speak.

Ok, well, I'll take it apart from the back side and get to those plungers and see what I see.

Thanks much for the tips.

 

[thepumpguysc]

Did u happen to see the slot on the barrels u removed.??
They HAVE TO SLIDE ONTO A LEAD PIN..
If u just dropped them in and tightened up the “top nut” u sheared the pins off..
U might as well stop now…
There’s nothing in the pump u can repair, other than a leak..

 

[gstrom99]

Welcome to TBN. It's rare for an injection pump to just quit. Like someone else said, you may be "premature" on the Dx. I know you said fuel "flows freely", but did you check/remove/replace the fuel filter first? Check all the hoses for cracks? Bleed the lines at the injectors?

 

[Chuck_L]

I hear you gstrom.

Everything is clean from the tank to the pump. No obstructions, no way for air to get it. The flow is smooth, bubble free, and strong.

Here is an observation: I disconnected the fuel line to the pump and removed the hollow bolt with the bleed screw. So at that point I was looking at the bare input orifice of the pump, with fuel all the way to the top of it. I cranked the engine and watched the level. It slowly decended as the 3 injectors "spit" tiny amounts of fuel out. This told me that something was amis, unless the system needed some amount of head pressure to keep things primed and pumping. So I reassembled everything, bled the lines, and used the exhaust port from a shop vac to put just a bit of pressure in the fuel tank and see if it would affect the situation in some way. However it didn't make any difference, better or worse.

But, thank you for confirming my suspicion; "It's rare for an injection pump to just quit." Now that makes sense to me.

 

[dodge man]

There is often a lift pump, just a small pump to get fuel to the main injection pump. Does your tractor have one and if it does is it working?

 

[Chuck_L]

Alright, I'm holding off on tearing the back side of that pump apart. I have my doubts that there is anything wrong with it, but I suppose we will see.

I figured maybe you kind gentlemen might provide me some feedback regarding the fuel flow I am getting, and what the problem with the pump actually looks like. So I'm going to try to post a couple of video links here:

Fuel flow video:

Injection Pump video:

 

[Chuck_L]

There is often a lift pump, just a small pump to get fuel to the main injection pump. Does your tractor have one and if it does is it working?

Nothing that is aparant. Here's what I see: fuel tank > fuel line > fuel filter > fuel line > injection pump.
The fuel filter assy has the fuel shut of valve built in along with two bleeding screws, one prior to the filter and one post filter.

 

[Chuck_L]

Did u happen to see the slot on the barrels u removed.??
They HAVE TO SLIDE ONTO A LEAD PIN..
If u just dropped them in and tightened up the “top nut” u sheared the pins off..
U might as well stop now…
There’s nothing in the pump u can repair, other than a leak..

Thanks; no I did not shear off the pins

 

[bmaverick]

Matt at the YTOG made this very informative video on the Yanmar fuel pump you have on the JD850.

If all that doesn't get you going, then the guy you've been chatting with here is,

Mike the pump guy - Master Injection Pump Rebuilder
For Japan made tractors, namely many of the brands including Yanmar / Deere for fuel pumps.
Mike can be reached on our message board from time-to-time, The best way is via email he typical monitors very often at:
thepumpguyscATaol.com
( replace the AT with the @ symbol when emailing please )
- Mike has 35+ years in the industry with injection pumps and hydraulic systems.
- He is very well versed in the JIS and SAE standards for parts to ensure proper components are used for rebuilds.
- From Sunny South Carolina.
- When sending parts via mail, please be sure to have insurance for a bit more than what you can find it new due to carrier issues that 'could' happen.
There are many positive testimonies on many of the Industrial Equipment, Heavy Equipment, diesel boating, tractor and other forums on his work and professionalism.
Shout out to The Pump Guy | Heavy Equipment Forums
(2) Thepumpguysc rocks - TractorByNet
Timing fuel injection pump - Yesterday's Tractors (yesterdaystractors.com)
Ford 3600 leaking from where fuel inlet meets injector | My Tractor Forum
The Pump Guy - Yesterday's Tractors (yesterdaystractors.com)

Mike has his exclusive repair info page at the Yanmar Tractor Owners Group.

 

[bmaverick]

Thanks; no I did not shear off the pins

FYI. as you mentioned the fuel filter+bowl and shut-off,

Yanmar Tractor Fuel Filter & Bleeding Video

Bleeding Yanmar Fuel System

All States Ag Parts is the leading supplier of tractor, combine, skid steer and other ag-related parts to North America. We sell new aftermarket, remanufactured and used parts.

www.hoyetractor.com

 

[careyo63]

There is a O-ring that goes around the top of the fuel bowl. Had mine go bad when I was replacing and cleaning the Fuel Filter. It was brittle and leaked enough so You could not bleed the Filter and bowl. Bubbles showed up trying to bleed the pump! Dirty filter and air in the line is a common problem. That's one super dirty filter in the #12 pic.!! What they should look like.

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And if your Running Red Die off Road Diesel it really hard to see the Filter itself for that matter. Check your rubber Lines for cracks/air leaks also. Make sure the one on the filter isn't pinched shut inside from the bend at the filter connection.

 

[Egon]

There is a O-ring that goes around the top of the fuel bowl. Had mine go bad when I was replacing and cleaning the Fuel Filter. It was brittle and leaked enough so You could not bleed the Filter and bowl. Bubbles showed up trying to bleed the pump! Dirty filter and air in the line is a common problem. That's one super dirty filter in the #12 pic.!! What they should look like.

Attachments

• 
  1678719056090.png

  4 MB · Views: 500

And if your Running Red Die off Road Diesel it really hard to see the Filter itself for that matter. Check your rubber Lines for cracks/air leaks also. Make sure the one on the filter isn't pinched shut inside from the bend at the filter connection.

 

[Egon]

If there is a solenoid in front of the Injection pump check to see if there is a thermistor involved in controlling the solenoid.

The solenoid disables the injection pump. They as ten dollar or so item for the the thermistor. The solenoid gets more expensive.

 

[bmaverick]

If there is a solenoid in front of the Injection pump check to see if there is a thermistor involved in controlling the solenoid.

The solenoid disables the injection pump. They as ten dollar or so item for the the thermistor. The solenoid gets more expensive.

Nothing like this on a vintage Yanmar made into a Deere. Not even a computer.