Failed injection pump?? what to check?

DrRighteous · Jul 1, 2019

Man, talk about strange timing
I've owned this AC 5020 for about 3 years now and it has mostly been trouble free. It never failed start or run nice. BUT, the moment I decide it is time to sell it, it dies.
I was preforming 1 last task before I was going to put the for sale sign on it and park it next to the road. I was going to pull my trailer out and ready it to pick up this tractor's replacement.
(Kubota 3301). It had the tow bar on it and backed it up to the trailer to pull it out of the woods. As was cranking on the trailer jack I noticed the tractor was idling kind funny, like it was going to stall. It has never done that since I owned it. I hooked the trailer up and jumped back on the tractor, and got about 10 feet before it died. It turned over, no start. Not a putt.
I checked the fuel. Half a tank. Check the valve and clean out bowl. All good, good fuel flow. Removed the filter, clean. Good flow to the filter. Went to the other side and removed the banjo fitting off the injection pump, good fuel flow to the pump. So my lines are not clogged. I backed off the line fittings to the injectors figuring somehow I had air in the system. Cranked, and cranked. Several attempts. Never a squirt from either line. The injection pump is getting fuel but just isn't working.
For this little tractor it doesn't get any simpler. There is nothing electrical except the starter circuit. That obviously works. The shut off control isn't stuck, working fine. So if it is cranking, it should be pumping but it is not. I'm not a diesel expert by any means and I do not know what else to check except to guess the injection pump is bad.
The engine is a 2cyl S126 Japanese diesel engine.

Any suggestions? Are these pumps easily repairable or should I look for a rebuilt pump?

TnAndy · Jul 1, 2019

Injector pump and easily repairable don't go in the same sentence unfortunately. Since you're pretty certain fuel flow is good, and the manual (I'm assuming) shut off cable/lever are working normally, does sound a lot like a pump.

Wait for pumpguy from South Carolina to see this (or PM him) and advise, as that is his specialty.

thepumpguysc · Jul 2, 2019

Get some compressed air & "back blow" the line from the pump to the fuel tank..
Then your going to have to bleed the air from the lines..

DrRighteous · Jul 2, 2019

Well, this one was my screw up.

I remember it wasn't long after I purchased this tractor I ran it out of fuel (no fuel gauge) and then had to purge the air from the pump and lines before it would run again. Ever since then I always kept an eye on the fuel level so that wouldn't happen again. I TOTALLY FORGOT that you have to turn that hex head screw in the side of the pump to purge the pump BEFORE you loosen the injector lines to purge any air in the lines. So I took my lunch hour and did just that. The tractor started up immediately and runs nice again. Now HOW it got air in the fuel system I have no idea. It had plenty of fuel and everything was clean and tight.
The only theory I have was that I used my pressure washer on to make it look somewhat clean. The cut off fuel valve on the clean out bowl ended up about a quarter turned but NOT in the shut off position. Could be this starved the pump of fuel and caused the problem to start with.
Anyway, thanks for the help guys. We are good to go.