New here. Need help with jd 755 (engine and injection pump) pics

[Cw021382]

Hi everyone. I知 new here, and new to the 755. I知 not, however, new to engines, diesels, or heavy equipment. I致e just acquired a mid 90痴 jd 755 with 2400 hours. It has the 3tna72uj engine, and what looks like a 719621-51100 injection pump. The tractor had diesel in the oil when I bought it, and does not run. If you turn the key on the electric fuel pump runs continuous and pumped diesel into the crankcase thru the ip. I drained the oil which was mostly diesel, and unplugged the electric fuel pump. The oil in the filter had a few fine pieces of metal in it. I Then removed the glo plugs and ran a compression test. I was surprised, it has 400 psi in all 3 cylinders. I then removed the tops from the ip. Two of the small pistons were broken, and 2 of the copper seals were missing. The 3rd copper seal was off center and had been stamped and deformed. I then pulled the ip. I had to pry the lever on the side of the pump with a screwdriver, to center to remove the pump. It痴 virtually locked. After removing the pump I found where the copper seals went. They were chewed to bits laying in the bottom of the pump housing (see pic below). So now I知 trying to decide what to do. Should I rebuild the ip, clean the fuel system, put new oil and filter in and see if it runs? Drop the pan and check the rods and mains first? If you read this far thank you, and any advice or insight is appreciated.

-Chris

 

[Roadworthy]

With the fuel issue I bet it didn't run long with the diluted oil in the crankcase. If it was my tractor I'd probably fix the injection pump and go from there. However I'm not a diesel mechanic so I'd probably pay someone else to rebuild the injection pump for me.

 

[thepumpguysc]

By removing the delivery valves from the ip, u allowed the barrel to rise from its seal & locating pin..{not good}
U either have to send it out for rebuild or do it yourself..{not recommended}
I would repair the ip & have the injectors tested BEFORE I fired it up..
Were the springs just broken on the DV's.?? or were the dv's themselves broken.??
U can click on my screen name for contact info, if u like..

 

[thepumpguysc]

If u go over to> tractor forum dot com.. someone JUST uploaded the 650-750 repair manuals.!!!
u have to join 1st.. then at the top of the page is a "MANUALS" tab.. theres all the info you'll need..
It might be worth having the pump rebuilt soley for piece of mind, knowing its GOING TO WORK when u put it back in..
DONT FORGET about the injectors.!!

 

[Cw021382]

Thanks for the responses. I have the jd technical repair manual. The springs in the DV were good. The delivery valves themselves are broken, and the seals destroyed. I only removed the dv because two of them were slightly loose already. I can’t rebuild the ip, but if parts are available I could rebuild the delivery valves. Wouldn’t the pump have copper shavings internally since the seals were destroyed? I’ll take some pics of the delivery valves and post them.

 

[Cw021382]

Ok here are the pics of the delivery valves, and some of the tractor if anyone is interested. Are the parts available to rebuild the dvç—´, and would that be a good option? The pump did prime and actuate one injector prior to me removing it. Also, would the bad dv let fuel pump into the crankcase or would that indicate more internal ip damage? What would cause this kind of damage? Bad fuel, defective parts, or something else? Thanks.

 

[Cw021382]

Here are the pics of the tractor they would not load in the last post.

 

[Cw021382]

I can only figure that the delivery valves fatigued over time and broke. Even if someone removed them I don稚 see how they could have installed them where the dv holder would have broken them when tightened down. The springs etc... were in place when I removed them. I priced new parts from local Yanmar dealer.
O ring 1.79
Spring 2.19
Dv assembly 47.57
Copper gasket 1.59

So with tax about 175 for parts to rebuild the delivery valves. Is it worth a shot to hope the pump is good? The parts have to be bought for a rebuild anyway and could be reused, except for the gaskets and o rings. Thanks.

 

[thepumpguysc]

Are u familiar w/ the saying>> Just because u can, doesn't mean u should..??

NO, its not worth a shot.. U can cause way more damage to the pump that u realize..
Just from the pictures I can see #2 tappet is stuck in the UP position..
So either u have a broken return spring or the plunger is stuck in the barrel..
Which means the control rack is stuck.. IF IT ISNT stuck & it moves back & forth..
either the rack is broken or the segment is..
U prob. need to stop..

 

[Cw021382]

That’s sound advice. I figure the pump will cost 6-700 or more to rebuild with the broken parts. I didn’t pay much more than that for the whole tractor. I don’t know for sure if the hydrostat or engine or 4x4 are good either. I found a really low hour (250) complete running engine for 975. I may buy it and pull the pump, and keep the rest for parts. Decisions, decisions....