I think my 1572 is jealous of the new 1772

FrankF3 · #1 08-26-2014, 10:14 AM

So, I got my new 1772 about 3 weeks ago. It is running well and I am just getting to the point of getting ready to mow with it. I think my 1572 is getting jealous and starting to throw fits. My wife said after I was done mowing that it behaved the same way for her the week before but she forgot to tell me about it and with this episode she said she sees a pattern developing.
I have a decent sized yard to mow, a little over 2 acres. Well the 1572 runs fine for the first hour and a half or so, then I swear the engine slows down a bit, first unnoticeable then more drastically. After it starts behaving this way, the fits happen more often in frequency. Basically, the engine slows right down as if it has no fuel, if I stop the forward motion with the tractor, sometimes it gradually recovers engine speed, sometimes is does not and the engine stalls. Sometimes after stopping going forward, and trying to recover I will disengage the deck. Sometimes this is enough, on several occasions the engine starts belching heavy black smoke while recovering and I can smell raw diesel with the exhaust.

The strainer in the tank, and all the filters were replaced within the last 2 months. Since I had the problem with the algae with one of my diesels, they all drink form the same tank that has been treated with biocide. What does this sound like to you. I am looking for any and all suggestions. Could it be the injection pump on the way out? If so, what are typical symptoms of a bad injector pump?

Sam Mac · #2 08-26-2014, 10:39 AM

Generally black smoke from a diesel is caused by, lack of air, too much fuel or lugging.

FrankF3 · #3 08-26-2014, 10:51 AM

On the 2- 3 times when it was sitting there, running at 1/4 to 1/2 speed, the hydro was set to neutral so there was no forward or backward and the deck was off. I remember 1 time in particular as it was happenning , being puzzled wondering where do yuo start to diagnose this. The engine when being restarted, spins over normally and does not turn over slow as if something is binding. It's either too much fuel or like you said Sam, not enough air.

Sam Mac · #4 08-26-2014, 10:55 AM

When was the last time you checked the air cleaner and the screen?

FrankF3 · #5 08-26-2014, 11:13 AM

Every spring before I start for the season, it get a new air cleaner whether it needs one or not and everything is all cleaned out. My wife said it start out running fine but after an hour to an hour and a half, the trouble starts. If I wasn't getting fuel, I could explain the loss of power and slower engine speeds, but when it starts belching out black smoke, there's too much fuel to burn. I'm going to have to see if I can find a Kubota D600 Engine workshop manual for reference. If I remember correctly there was a troubleshooting section in it. However it was like using the shotgun approach in that you will eventually find the problem byt replacing lots of parts.

Sam Mac · #6 08-26-2014, 01:43 PM

Link for the Bota service manual.

http://www.onlycubcadets.net/forum/s...ead.php?t=4660

FrankF3 · #7 08-26-2014, 01:59 PM

Thanks Sam. I'm going to double check the filters out just to rule them out as well as for a malfunctioning low pressure fuel pump.

J-Mech · #8 08-26-2014, 02:19 PM

Black smoke as a general rule is just as Sam said. HOWEVER, it can also be caused by timing, and low injection pressure.

Since you seem to have all your bases covered, the filters are relatively new and you have cleaned the fuel system, there are a couple places to start.

Here's where I'd start:
*Check to make sure you don't have a fuel line collapsing internally.
*Make sure the charge pump is working.
If those are fine;
*Check the return line. Make sure it's good.

If you still can't find any problems, start taking the fittings out of the injection pump. Take the inlet out first (see pic). Make sure the small hole in the "bolt" isn't plugged. While it's off, turn the key on and let some fuel bleed out of the line to flush it.

IMG_20140826_130635.jpg

After that, pull the return fitting. (See pic) As you can see, it has a very small hole in it. With the inlet line all reassembled, and hooked up, return fitting out, again cycle the key and flush fuel through the pump. This will flush out the inside of the pump. With the problems you have had with bio-fuel, you may have junk in the pump itself.

IMG_20140826_130819.jpg

Report back if all that doesn't fix it and we'll go from there. You should never "shot-gun" any repair. I have never seen a book that said to replace parts without telling you how to test them first. There is a test and a procedure for everything. Diesel motors are too expensive to just start replacing parts. I highly doubt you have a failing injection pump. The pump is a mechanical pump, and if it was broke, it would be broke. It wouldn't work for an hour and then suddenly quilt. It just wouldn't work at all. Keep us updated.

FrankF3 · #9 08-26-2014, 02:34 PM

Thanks Jonathan. I'll start digging into it and see what I can find. All of those fittings you show were last touched when assembled at the factory. What really puzzles me is that if only happens after it gets hot or after about 1 1/2 hours of running......

J-Mech · #10 08-26-2014, 02:45 PM

I've seen stranger things. I'm betting either the electric pump is getting hot and not working, or a return line is plugging. Might check the fuel cap too. May not be venting......

For the record, and better explanation:
The reason why fuel starvation (like a weak electric pump) causes it to smoke is because the plungers in the injection pump can't "suck" fuel. If they aren't being filled with charge pressure, they can't or won't fill all the way. When this happens, they don't inject fuel at the correct time, or the proper amount. That's what makes it smoke. I'm not 100% sure this is what's going on with your machine, but it fit's the bill.