M7040 Smoking with Fuel in Oil - help

[dmann33]

So, my barely 1 yr old Kubota M7040 starts putting out blue smoke when running at any RPM, otherwise it starts and seems fine. I change all the filters including both air filters and fuel filter. A little better maybe, but not much.

Take it to dealer and they reported unburned fuel was going into exhaust and making black smoke and blue smoke was caused by unburned fuel bypassing the rings and thinning the oil in the crankcase. They hooked to a remote fuel supply, but problem continued. Emission equip checked ok, but checked individual cylinder exhaust temp and found front cylinder cold.

They then found front cylinder to have low compression, but valve backlash ok.

They then filed a pre-claim with Kubota on the basis of "low compression on front cylinder, front cylinder running cold and unburned fuel going into exhaust and crankcase."

Kubota finally responded after 4 days with the following:

"Compression is low, but within 10% spec of other cylinders, but the rings are so bad your dumping oil into the crankcase. At this point low compression and ring issue is not enough to validate warranty. At 729 hours this sounds more like a dusting and than a factory defect. Please tear down and inspect and validate a defect, but keep in mind if no defect is found then customer will be responsible for total repair bill."

What a crock! Its going to be about $1000 just to do this inspection. (Edit: technically $2000 for tear down and rebuild)

What I really don't understand is how could the front cylinder possibly not be firing (and therefore burning this fuel) if the compression is within spec? I'm waiting to find out what the compression actually is. I might possible have a failed intake gasket (letting air in and dusting the cylinder), but it should still be firing if compression is within spec, no?

My private mech (non-warranty stuff), suggested that the injector may be bad and overloading front cylinder with fuel to the point it would not fire. That would not explain the lowered compression, but can fuel still get in the crankcase if the rings were ok?

Any thoughts out there. I really need my tractor back.

 

[North Idaho Wolfman]

By what you explain I would think bad injector too.
Bad injector can wash the cylinder and cause bad fire, low temp, and fuel ending up in oil, and oil ending up in exhaust.
If the compression is within 10% of the other cylinders I would also think bad injector not bad rings.
Yes a bad intake gasket can cause dusting but I would think it would be very obvious that it's bad and that it would also cause dusting on all cylinders to some extent.

 

[Tx Jim]

Before I consented to engine tear down I want the injector pop tested and cyl head valve clearance checked.

 

[kuboman]

A bad injector sounds like the culprit to me. It can cause all kinds of damage including scored cylinder, damaged piston,worn rings, diluted oil and smokey exhaust. Bad deal all around if not caught right of the bat. Dirty, contaminated fuel most likely to blame but sometimes injectors just fail.

 

[dmann33]

UPDATE:

I was able to get the compression data from the dealer as follows:

475, 500, 505, 500.


I'm probably going to ask them replace the injector before pulling the engine and breaking it down.

At 475 psi I cant understand how that cylinder wouldn't be firing fine unless the injector was bad. Dusting or no dusting that cylinder should still fire, No?

 

[Tx Jim]

UPDATE:
At 475 psi I cant understand how that cylinder wouldn't be firing fine unless the injector was bad. Dusting or no dusting that cylinder should still fire, No?

Yes 475# compression should ignite the diesel if injector is misting fuel correctly.

 

[dmann33]

@TX Jim - Thanks, That's what I figured. Also, what would the cyl head valve clearance tell us, and with a compression of 475# do you think that should still be checked?

@Kuboman - a bad injector can cause bad rings and scored cylinder? Can you or someone explain?

 

[North Idaho Wolfman]

A bad injector that is washing the cylinder walls will cause it to wear very quickly, as it's not maintaining proper lubrication for the rings.

I would have the valve clearances checked, Bad valve seating will cause low compression too.

 

[dmann33]

UPDATE:

Dealer called this AM after discussing with Kubota warranty administrator. Admin claimed that the reason the previous warranty tech requested the tear down was that they've known over fueling to cause a connecting rod to bend. Should they have found a bent rod, they then would have ordered the injectors replaced (and possibly pump, can't recall). The administrator was happy to order the injectors and pump pulled and sent to the NC warranty processing station.

The fuel pump timing has also been questioned by some, but I suspect that will be verified when its all reinstalled.

Will keep you all posted.

 

[kuboman]

A bad injector will stream the fuel instead of misting, cause washing of the cylinder walls and hot spots on the piston. I have seen pistons with holes melted in them because the injector was streaming the fuel. Check the valve clearance but I am betting the rings have worn some. Pull the injector and have it checked.

 

[dmann33]

Update:

So the Kubota processing center in NC fully tested my injectors and fuel pump and reported the work perfectly fine. Arg!

I expect that Kubota will now want to break the engine down. Prior to the test results of the fuel system, I was informed that Kubota has known overfueling to bend a connecting rod, however, I suspect they don't think that to be the problem now.

Can anyone possibly explain to me why this front cylinder would not be firing if it has satisfactory compression and proper fuel delivery? What on earth could they find by breaking down the engine?

I'm very frustrated and need my tractor back!

 

[kuboman]

Makes no sense. Assuming they did all the test correctly. It would not be the first time a shop messed up. I am not saying that this is your case but it does happen on a disturbing regular basis.

 

[dmann33]

Update:

I'm disturbed alright. They've now scheduled the factory Kubota tech to come and work on it. Apparently, the soonest he could come is another 13 days from when the fuel components had checked out ok.

Add it all up - That will be day 50 from the time that I "got in line" to get the tractor repaired. Maybe, just maybe, Kubota can tell me why my 1 year old tractor is only running on 3 cylinders after 50 days.

Unbelievable isn't it?

 

[Daren Todd]

It really sounds like the injector was sticking and over fueling the cylinder. Which a quick bench test may not show. See if they can swap that injector to another cylinder and see if it moves with the injector. It seems these dealerships are getting their hands tied by corporate over warranty issues. Kubota isnt the only company where their techs have to submit to corporate for approval over warranty claims. And it really sucks if you happen to be the first person with that issue showing up and the warrany tech department hasnt come up with an approved solution for it. I ran into a similar issue with jd over a harmonic balancer belt pully with the wrong number of grooves. The dealership agreed it was a warranty issue, but couldnt do the work till the warranty department could come up with the fix. It ended up turning into a recall for a bunch of motors, but took some time

 

[Daren Todd]

Question
I'm not familiar with your tractor model. Does your tractor have an ecm that controls the motor or is it a mechanically governed system? If its got an ecm, there may be an issue with the computer telling the injector to stay open a little longer then the the others!! Or a bleed in the wiring harness some where causing it to stay energized

 

[dmann33]

Question
I'm not familiar with your tractor model. Does your tractor have an ecm that controls the motor or is it a mechanically governed system? If its got an ecm, there may be an issue with the computer telling the injector to stay open a little longer then the the others!! Or a bleed in the wiring harness some where causing it to stay energized

I'm probably not qualified to give you a definitive answer, but I believe it does not have an ECM. I understand the fuel pump is timed to engine (cam) and said timing can be adjusted on the fuel pump's delivery valves which are essentially right on the pumps output of each injector line.

It has been suggested that the timing could have simply been off as its easily thrown out of time when if you were to loosen the injector line on the fuel pump to bleed.

 

[Daren Todd]

That seems really chintzy if you throw off your timing by bleeding the injectors. Hopefully the kubota man they r flying in can figure it out for you. I would have been losing my cool the the dealer if they had my equipment that long. Or telling me i had to pay if they didn't find anything wrong. When the equipment is still under warranrty. they had one of my light towers with a spun bearing for almost 5 months. But three months of that was arguing with them over if it was covered under warrantee because i didnt have service records for one oil change. A customer had it at the time and did the oil change instead of me.

 

[dmann33]

That seems really chintzy if you throw off your timing by bleeding the injectors. .

As I understand the injector line is attached to a fitting on the pump and you're supposed to hold the fitting with one wrench while you loosen the injector line. I'm told if you just try to loosen the injector line, you may also inadvertently turn the whole fitting (and that would throw off the timing).

Of course I haven't even seen my tractor in over a month, so I can't recall what it all looks like firsthand.

 

[kuboman]

As I understand the injector line is attached to a fitting on the pump and you're supposed to hold the fitting with one wrench while you loosen the injector line. I'm told if you just try to loosen the injector line, you may also inadvertently turn the whole fitting (and that would throw off the timing).

Of course I haven't even seen my tractor in over a month, so I can't recall what it all looks like firsthand.

But the pump was checked, correct? Any competent pump tech could spot that in a heart beat. It would also show up with a flow check.

 

[North Idaho Wolfman]

As I understand the injector line is attached to a fitting on the pump and you're supposed to hold the fitting with one wrench while you loosen the injector line. I'm told if you just try to loosen the injector line, you may also inadvertently turn the whole fitting (and that would throw off the timing).

Your thinking it's like an old distributor on a car, it's not!
Removing or reinstalling the lines would have Zero effect on the timing.