Originally posted by Morphious
I have an old JD Industrial tractor that ran great all summer bailing hay with it. Went to use it back in sept-oct sometime and started it, walked away to let it warm up, and it died. Didn't have time to really mess with it then, figured it was the fuel filters. Well, went out today with some free time and changed the filters, bled the lines to get the air out of the system, and bam, same thing. Ran for a few minutes and then shut down. I have narrowed the problem down to the injection pump. After fiddling with it for an hour or so, I broke loose the return line from the injectors to make sure there was no air in them, and started the tractor, it ran fine, when fuel started coming out of the return line, I replaced the line and tightened it down, the tractor died. Repeated the process, tractor ran as long as the line was loose and spewing fuel, as soon as I tightened the line up the tractor would die. I think what is happening is the pressure is building up on the return line. I think that the bypass valve is plugged up. What I need to know is what I need to do to unplug/fix this problem. Any help on this would be greatly appreciated.
Morph.
Hi. Hope you have some spare change lying around. This one's going to cost you.
The return piping is plugging because there is a little plastic ring inside the pump that cushions the drive weights from engine pulses. This little ring has a finite life - somewhere in the 2000 to 5000 hour range and then it finally gets so brittle it cracks and breaks up. The bits and pieces run through the works inside the pump and get ground up something like coffee grounds, and when they get small enough, they flow to the outlet with the return fuel and plug it up.
Now, yes, you can just clean it out and it'll start up and run... BUT, if you do that, it will be only a short time before the governor cage rivets let go and the governor ceases functioning. Now, on the minor side, this results in your tractor dying at idle. OR, it runs away, with no governor control at all.
On the major side, 2 of the rivets break or the cage wedges outward with a chunk of flex ring and, since it's a round device spinning in a round housing, it suddenly discovers the wall of the housing and the steel burrows into the aluminum housing, stopping it's rotation. This can cause sideways thrust on the rotating pumping parts, and seize the head and rotor, turning your $500 simple rebuild into a $1200 pump PLUS a $75 drive shaft which breaks to save your engine gears from stripping out.
Why, you ask, is it in there? Well... it usually lasts till the pump is worn out anyway... And, it was cheap to make. In all probability, many other parts of your pump need attention and the seals are ready to take a dump...
Now... If you keep trying to run it, it'll probably blow the seals out of the pump and start pumping fuel into the crankcase...
So, after you've found the obstruction in the line and cleared it, look for evidence of these "coffee grounds". If you find it, you know what you need to do. If you don't, you can remove the top of the pump and look into it. (3 screws, oblong cover with the return fitting in it) If there's nothing in there, then don't worry... if there is... sooorrryyy... The lines from the injectors normally join the return back to the tank and the line is pretty short. It should return to the top of the tank... Try taking the line off the pump and cracking it at the injector returns and blowing compressed air through it backwards from the tank end to see if you're obstructed and/or clear it out.
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