Oil & Fuel BX2350 Running Rough and Smoking

[GA06BX2350]

So, I got a bit busy with the kids today so it looks like the compression test will have to wait until tomorrow. Before I start this test, I did have a suggestion that I wanted to run past you guys. A friend of mine was a diesel mechanic in the military and when I told him I was going to do a compression test he suggested that I do a "blowback" test first. Apparently it's a rather common, quick and simple test. The general thought behind the test is that pressure takes the route of least resistance. On the compression stroke, if the exhaust pushes past the piston rings, then it will take the path of least resistance out of the crank case. If the oil cap is off then that route is generally the oil fill cap. Now, while it won't detect a problem with a particular cylinder, supposedly it will tell me if I'm having a ring leaking problem in general. My questions...since this is such a small engine will this actually work?
My thought is that this might catch a problem with rings, but not the pistons or connector rods. I appreciate your input.

Thanks,
John

 

[Recoveryhill]

Blowback would occur if you had a cracked piston, damaged rings or cylinder wall. You can't manage what you can't measure and I don't know any way of measuring the result of a blowback. A compression test will give you specific numbers for air pressure in each cylinder and if low, a method to guesstimate the location of the problem. You are correct in assuming that a bent rod, resulting in lack of sufficient piston travel in the cylinder will not create blowback. Again, I just hate to be the messenger but bent connecting rods would be a risk in any hydro-locked engine. The strength of the rods that transfer power from the combustion zone to the crankshaft are designed to withstand the pressure in the cylinder of a precise volume of compressed air. They are not designed to withstand the increase in pressure that occurs when there is liquid in the combustion chamber.

With the injectors out, you can also measure the depth of the piston face while at the top of it's stroke and compare to factory value. That's going to require a dial indicator though and even a relatively small differential will cause combustion problems so the measurement needs to be very precise. Mount indicator on engine with probe extending into cylinder. Rotate piston through full travel and note the travel number (height of stroke) and record. Repeat on each cylinder, mounting indicator in identical plane with probe arm unchanged in position. If any piston travels less distance, it's a rod. For this you would rotate engine by hand only, not with the starter motor.

If you have the specified pressure in each cylinder though, that and anything else related to the combustion chamber is not your problem.

Were it me, it would be out with the injectors and in with the pressure gauge. This will define your conditions in each separate cylinder.

 

[GA06BX2350]

Understood. Thanks!

John

 

[GA06BX2350]

So today I finally got the chance to work on my tractor. Since I was going to have to remove the injectors anyway I decided to go ahead a replaced them (got a great deal, 3 for $135). I removed the first injector and tried to screw in the compression tester adapter........it doesn't fit and the store is closed for the day. Still, it wasn't a total loss. After removing all the injectors I noticed that one of the cylinders had hard buildup in the hole where the nozzle fit's into the cylinder. In this indicative of anything? Could it be that the injector isn't able to spray a good pattern so the engine isn't running correctly? Any suggestions on how to remove the buildup? Thanks for the reply. I'll also let you guys know about the compression as soon as I get a new tester.

Thanks,
John

 

[Gator6x4]

When I read your post I starting thinking someone told me the Harbor Freight Diesel Compression checker used the GLOW PLUG HOLE. So I goggled it and sure enough I still have a little creditable memory. Please read the information in the attached. Compression Test Adapter - OrangeTractorTalks - Everything Kubota. Good luck.

 

[Recoveryhill]

After removing all the injectors I noticed that one of the cylinders had hard buildup in the hole where the nozzle fit's into the cylinder. In this indicative of anything? Could it be that the injector isn't able to spray a good pattern so the engine isn't running correctly? Any suggestions on how to remove the buildup?

John, The build-up is carbon from un-burned hydrocarbon, fuel or oil. I can't say whether or not a faulty injector would produce this but if there is considerable buildup of this material in the combustion chamber it is going to affect your compression test. My paranoid self thinks.....low compression due to bent connecting rod causes partial combustion of injected fuel, lack of power and smoke. You would see low compression. Hmmmm....significant build up of material in the combustion chamber reduces volume of chamber and raises compression even if piston travel is reduced. (I probably think too much).

I'd just go ahead with the compression test and pay close attention to the affected cylinder. If compression is good, there must be a solvent that can be injected into the cylinder to help dissolve the carbon. Make sure if you add any solvent that the glow plugs and injectors are OUT of the block so as not to have accidental combustion and to allow the crud to blow out. Since you are using the glow plug port for the gauge make double sure the fuel is shut off to the re-installed injectors. If you do have low compression in that cylinder, regardless of the carbon, don't forget to try injecting a bit of motor oil into the cylinder and check compression again. Broken rings would allow crankcase oil into the upper cylinder and if a shot of oil raises compression, look to sleeve, piston or rings. In any case, after I got the carbon out of the cylinder I'd check compression yet again unless it's low to begin with even with the carbon up there.

Perhaps someone else has direct experience with either the cause for the build-up or how to remove.

 

[Recoveryhill]

OK then, I'll continue:

Carbon removable from static engine parts: Chlorinated brake cleaner (tetrachloroethylene) will remove carbon from substrates. (harmless to aluminum parts)

Carbon build up removal in a running engine: Seafoam

Still hoping those compression numbers are right in line?

 

[GA06BX2350]

Thanks for all your help so far. The compression testing kit from my local Harbor Freight store had the same item number as the one mentioned above but looked totally different. It even looked different than the one at HF online. Nothing in it fit the hole for the glow plug or the injector. So, I finally broke down and took the tractor to the local dealer. Unfortunately you were right, it is losing compression on the number 3 cylinder (closest to the front of the tractor) and there is a lot of carbon build up in that cylinder. They called me this morning with a series of estimates to fix it. They feel confident that it's not the rod or valve. They think it's a cracked ring but just in case they want to send out the head for testing. If it's a cracked ring they will fix it for ~$1200, labor is major cost as they estimate 10hrs at $80/hr. If it's the piston itself the cost is ~$1450. If the head is bad, the cost for the piston, ring, and head is ~$2650. An entirely new engine, which is everything, would be around $4000. The mechanic said he truly thought it would be the ring, but he's not 100%. I'm already in to them for $200. To me that all seems a bit high, but then again I've never had this sort of work done before. I would love to have someone elses perspective on this.

As always I appreciate the input.

John

 

[GA06BX2350]

By the way, I've asked for the exact compression numbers but the mechanic didn't have them in front of him. I'll post them when I get them. One thing that still confuses me is that there was no blowback. If there was no blowback wouldn't that make the ring / piston an unlikely culprit.

Thanks,
John

 

[rbarker]

Thanks for all your help so far. The compression testing kit from my local Harbor Freight store had the same item number as the one mentioned above but looked totally different. It even looked different than the one at HF online. Nothing in it fit the hole for the glow plug or the injector. So, I finally broke down and took the tractor to the local dealer. Unfortunately you were right, it is losing compression on the number 3 cylinder (closest to the front of the tractor) and there is a lot of carbon build up in that cylinder. They called me this morning with a series of estimates to fix it. They feel confident that it's not the rod or valve. They think it's a cracked ring but just in case they want to send out the head for testing. If it's a cracked ring they will fix it for ~$1200, labor is major cost as they estimate 10hrs at $80/hr. If it's the piston itself the cost is ~$1450. If the head is bad, the cost for the piston, ring, and head is ~$2650. An entirely new engine, which is everything, would be around $4000. The mechanic said he truly thought it would be the ring, but he's not 100%. I'm already in to them for $200. To me that all seems a bit high, but then again I've never had this sort of work done before. I would love to have someone elses perspective on this. As always I appreciate the input. John

Sorry to hear that it's internal damage, that's a shame. Now you really have to play crystal ball and try to guess what they are going to find once they get it opened up. The prices quoted don't seem too out of line to me but as I got closer to the price of a new motor I would lean heavily in that direction. Too bad you won't know for sure until they get pretty deep into the project.

Good luck and hope for the best!

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