Thomas Skid with Kubota v1902b engine problems

[RobMonk]

I have had my old Thomas for about 9 months now and I have been enjoying it, I don't use it all that frequently so I have a hard time gauging if changes happened over a long period or over night.

Yesterday I was using it to dig out of a big snow storm and I noticed it was making a sort of knock but I would call it more of a 'ticking'. It sounded like it was small/light pieces creating the issue, in fact I checked several times to see if it was the fan hitting the shroud. The ticking increased with RPM but after a while I just figured that I didn't notice it before because I always wear hearing protection. It seemed to have a bit of an issue reaching full power but it did the job. Today I jumped into it to do a neighbors driveway and I got it all done (10minutes) and just at the end the sound disappeared and there was more vibration and seemingly less power.

I turned it off immediately to check to see if perhaps the serpentine broke (as I suspected the fan as the noise culprit) It wasn't broken and so I decided I would start it and make a B-line for home. It wouldn't start as the starter had a hard time turning it over. I have been experiencing this lately and if I let it sit for 10 mins or so it starts no problem. Anyhow I got it home and the engine seems to be shaking quite a bit which I would guess as on cylinder not firing and so when it was cooled down I put a pile of snow on each of the exhaust manifold legs and 3 of them melted near immediate and the 4th took a while to melt and then stayed wet for a few minutes while the others were dry as a bone.

So. I am thinking injector nozzle? But I'm not sure that explains the ticking from earlier and does it make sense that would stop working in an instant? Thinking about it, I did notice an increase in the amount of smoke coming out of the stack before it broke. If it is that, is there a way to test the injector to verify that? My friend works with diesel engines and his work has an injector crew that handles the testing of injectors but he doesn't know how it is done himself but the tech is available to him. I am guessing he would need specs? Has anyone had experience with replacing injectors on these engines (or similar engines)? Is it a big job or as quick as it looks?

Any suggests would be appreciated

 

[Moonlite]

What color is the smoke?

 

[willie59]

I'm not familiar with the particular Kubota you mention, but I assume it's a multi cylinder engine. You're thinking (hoping) it's just a bad injector. In fact, injector failure is a common thing. You don't need specs or high tech stuff to deal with this. Start the engine, run it at the rpm you feel the "shake" you describe. Crack open the fuel line connection to each injector. A good injector will now cause a noticeable "miss" when you crack that injector nut, a bad one will not make a miss (much like plucking plug wires on a gas engine searching for the failed cylinder). Once you find the failed cylinder/injector, pull that injector. Then pull an injector from a cylinder that tested good, switch those two injectors. Start engine and test again. If the "miss" moved to the cylinder that previously was good, you have a bad injector. But if the miss remains at the original problem cylinder, you have a problem with that cylinder.

 

[RobMonk]

So I took out the injector and gave it to a friend who has the tech to figure out if something is wrong with it. It was spraying at a good pressure and it was deemed that "it should work". They cleaned it and re-laped it anyhow and we put it back in with no change. The weather warmed up recently and I was able to get it started again and move it around there was a smell of fuel in the air when I was going up hill and clouds of smoke when going downhill. I am now working on the idea that it is a valve, particularly the exhaust valve on that cylinder not allowing the engine to get compression and the fuel is getting into the manifold and its destination changes based on the tilt of the machine. I am hoping be able to tell this with the valve cover off so I don't need to take the head off and get a new gasket, but time will tell.

Does anyone else have an idea of what it might be?

 

[Delmer]

By all means pull the valve cover off, check for out of place pushrod, valve clearance, sticking valve. If nothing is obvious, I'd say it's time for a compression test, and then a second time with oil to test the rings.

 

[mikebramel]

By all means pull the valve cover off, check for out of place pushrod, valve clearance, sticking valve. If nothing is obvious, I'd say it's time for a compression test, and then a second time with oil to test the rings.

100% advise

 

[RobMonk]

We are working towards diagnosis but we have run into something interesting that doesn't make sense. We were considering that perhaps it was with the injector pump. We took one of the injectors out and attached it the fuel line off to the side of the engine. The idea was f we turned the engine over it show spray fuel out of the injector (that we tested and found to be fine) if the pump was working. It didn't spray so we thought that must be the problem. Just ot be sure we did a second injector the same way, it also didn't spray. I know I had more than 2 cylinders so now I am trying to figure out why that test wasn't working. Does anyone know why that wouldn't work/a way to check the injector pump?

 

[frogfarmer]

I have seen guys try to check injectors this way and the results they got were typical for what you got. It is very difficult to observe the spray at cranking speed with the small amounts of fuel we are talking about. With the smoke and fuel you are smelling I would expect incomplete combustion due to low compression. A better way to check for flow from the pump is start the engine and crack the lines at each injector. Each line should give a strong pulse of fuel when the pump sends the fuel to the injector and the engine should drop off and come back when you tighten the line. Since you have a good idea which cylinder is weak start the engine and see what happens when you crack the line on that cylinder verses one of the others. DO NOT check for spray with your finger or any other body part. The spray pressures at the injector tips will pierce the skin and inject fuel into your flesh causing a very nasty infection and possibly death.

 

[Delmer]

Does anyone know a way to check the injector pump?

"Crack open the fuel line connection to each injector. A good injector will now cause a noticeable "miss" when you crack that injector nut, a bad one will not make a miss (much like plucking plug wires on a gas engine searching for the failed cylinder). Once you find the failed cylinder/injector, pull that injector. Then pull an injector from a cylinder that tested good, switch those two injectors. Start engine and test again. If the "miss" moved to the cylinder that previously was good, you have a bad injector. But if the miss remains at the original problem cylinder, you have a problem with that cylinder." (from Willie above)

Then if the bad cylinder tests OK for compression and valve lift then the problem is the in that injector pump. Assuming this is the kubota "inline pump in block" type, then I can't tell you how they work or what to do next.

 

[RobMonk]

So after the diagnostics were done it came down to this. There is 0 that's right 0 compression cylinder 1. The other cylinders have fine compression. My guess is that means there is something shot with the valve. When I had the valve cover off I tapped the valves as a quick way to check the lash (that is if there was any) and I later checked it with a feeler gauge and everything seemed fine. The head is coming off next so I can check into this theory.

The other thing I was hoping for someone to clarify something else about this engine that I am having a hard time figuring out. I hear lore of a decompression lever on these engines, yet I have not seen nor heard of where it might be one the engine. Does anyone know if the v1902 has one and if so could there be a malfunction that would lead to 0 compression in 1 cylinder?

 

[Delmer]

Never heard of a decompression lever on a multi-cylinder engine. Has anybody?

 

[frogfarmer]

Never heard of a decompression lever on a multi-cylinder engine. Has anybody?

Lots and lots of multi cylinder engines with decomp. Caterpillar made hundreds of thousands. I am not aware of a decomp on this series of Kubota and have not seen any Kubotas with a decomp.

Back to the point when the rod bearing goes it allows enough travel in the piston/rod assembly to smack the valves and all compression is lost. Also any failure of the valve or seat will cause compression loss. Pull the head and let us know what you find.

 

[RobMonk]

There is a video on YouTube with a getting the air out of the fuel lines on a Kubota, he says to move the decompression lever to aid in this, so yes Kubotas do have that function at least some of the engines.

What would I be looking for with the head off for the rod bearing. Also I don't see how a rod bearing would "go" to the point of allowing it to hit the valves. What is the thickness of a con-rod bearing, 30 thou? And that would only be if the thing disappeared.

 

[Delmer]

If you got 0 compression then I suppose there's no point in using oil, but a leakdown test should show you exactly where the leak is, intake, exhaust, or crankcase.

 

[frogfarmer]

What would I be looking for with the head off for the rod bearing. Also I don't see how a rod bearing would "go" to the point of allowing it to hit the valves. What is the thickness of a con-rod bearing, 30 thou? And that would only be if the thing disappeared.

If a bearing has failed it will likely be completely gone allowing the rod to ride on and wear the crankshaft. A clearance of .250 is not uncommon when a bearing goes and the motor continues to run. The piston will be well below the deck of the block when its at TDC. This may or may not be your situation you could have a valve or head gasket issue causing the whole loss of compression.

 

[RobMonk]

Alright. So a little over a week ago I finally got around to pulling the engine out and taking the head off... It wasn't good. I noticed one of the pistons wasn't oriented correctly. Pulled of the oil pan and it was pretty chunky in there. The con rod was doubled over and sitting in the out pan with chunks of the piston and a complete wrist pin. What had happened we discovered as we went on was that water must have come down the exhaust and into the cylinder and since water doesn't compress something had to give. Miraculously other than the cause of the problem, no there damage was done. The crank was fine and the journals were fine. I got all the parts (I am doing a proper rebuild while I am in here) yesterday and I already rebuilt the head (re-lapped all the valves, tested springs, cleaned up all the old oil and gasket surface, new valve seals) and honed the cylinders and tonight I will put the pistons back in and put it all back together and I am hoping to have it back in the SS on Sunday.

 

[frogfarmer]

You are very lucky nothing else was damaged. When I find something like that almost everything is bad. Glad to hear its on the mend. Hope your weather is better than ours it was 0*F here this morning.

 

[RobMonk]

When this initially happened I didn't think anything major was wrong so I moved snow with is to get my trailer out so I could take it to my buddy's shop as well as some smaller tasks... all this with a con rod and assoc. parts in the oil pan! My buddy is a diesel mechanic and both of us were sitting there looking at this engine vomit and trying to figure out how this could have happened and not done any damage.

Being stuck out in the Atlantic ocean like we are, despite being a lot further North than you, we have very similar weather. My guess (and it is only a guess) is that we probably have a bit warmer winters and a bit colder summers than you with more rain and snow. Sat-Mon are going to be warm though!

Does anyone know the torque specs for connecting rods on a v1902 engine?

 

[frogfarmer]

29 ft-lb