Smoking diesel mystery

[Tx Jim]

Lots of possibilities but I agree, you shouldn’t be able to compress springs by hand unless you are really strong.

I agree one shouldn't be able to compress cyl head valve springs by pushing down by hand.

I've read it's difficult to get new piston rings to seat in liners utilizing standard engine oil.

 

[kenmac]

leak down test on cylinder heads ? fuel leaking by the valves when they are closed ?
I agree you shouldn't be able to push down the valve springs by hand.
I have a valve spring compressor tool I used to change out the springs on my drag car.

I'm sure your springs probably should have better tension than on my race car

 

[ericm979]

Tractor valve springs are weak compared to a drag car or any car. Valve springs are there to keep the valve in contact with the valve train as the valve is opened and the cam allows it to close. When the springs are too weak the valve will "float" which means that it stays open longer than the cam would allow. On a spark ignition engine you can hear valve float as the valve train becomes loose and clatters. A diesel's noise might mask that.

With a small tractor diesel the valves are smaller and lighter than your drag car (or any car), which means there is less mass to slow and return to the seat. The cam lift is lower which means the valve is not accelerated as fast to begin with. And the redline is much lower which also reduces the accelleration of the valve that the springs have to handle. So the tractor valve springs should be much weaker than your drag car.

If it's the valve springs then I think they would have to be so weak that they would not seal at idle. Otherwise it would not smoke at idle and would only smoke when you ran the engine fast enough to cause float. And I don't think that mere valve float would cause smoke... when the valves float that just increases their open duration some. Tractor cams have really short duration already, a little longer is not going to cause float.

If the springs were so weak that the valves were not closing at all that might cause smoke but you would not have any compression.

I think it's likely something else like bad valve seals letting oil get sucked into the combustion chamber.

 

[Jerry/MT]

I have saved a Zetor 7045 from a farm where it had been sitting outside for over 20 years. The hour meter shows 2122 hours. The engine was seized, which was expected.

I have replaced the cylinders and pistons and the valves, I have ground the valves/ seats.
The injection pump is tested and adjusted and the nozzles are new. This was done at a certified diesel shop.
The tractor starts but smokes heavily, white smoke, not consistently on 3 cylinders. Three of the four exhaust ports are wet, one port looks fine (the port not smoking). The compression test shows over 300 PSI at room temperature. A test with a different tester showed 232 PSI at 21* Fahrenheit.
I have switched injectors from one cylinder to another, and the smoking stays with the cylinder.
I have been trying to locate this problem for over a year now. It would be nice to use the tractor this spring for planting.
I have no idea what is causing the 3 cylinders not to ignite correctly.
Now I am thinking that the valve springs might have lost their strength. I discovered that I can push the valve down by pushing on the spring retainer cup with my hands. This seems odd.

What do you people think?

View attachment 732285

Your compression numbers are very low especially since you rebuilt the engine. They should be above ~ 350 psi. Damaged valve springs and bent pushrods, bad valve quides, valve timing, ring seating, etc could be part of the problem. Assuming you set the valve clearance correctly, I think your concern about valve springs being "soft" warrants some further investigation.

 

[Egon]

Perhaps the piston rings did not seat properly. Does the oil level drop?

 

[Bayfisher]

do you have the manuals [ service and parts ] ?

if the tractor is in canada then the oil is incorrect for the climate.

being that u installed new sleeves and pistons the engine will need to be broke-in before
u get good compression #s, recheck the valve clearance as they may not be completely closing,
is excess fuel being returned to the tank ? is the oil bath/filter clean and at the correct level ?

 

[zegersfarm]

After the rebuilt, the compression was first tested in the shop because of smoke and was over 300 PSI. The tester maxed out at 300 PSI on all 4 cylinders. All cylinders have their own head and head gasket.
The tractor was driven to a field to be put on the disk. After disking for about an hour I quid because the smoke was to much. I didn't want to breath that.
Then I took the pump and injectors to a certified diesel shop. 4 new nozzles and the pump was adjusted.
When we had the injection pump back there was no change in the smoking. It was winter now.
Then I tested the compression again with a different tester, but now it was minus 21 Fahrenheit.
All 4 cylinders had 240 PSI at minus 21 Fahrenheit.

 

[California]

Have we determined that the white vapor isn't water vapor?

 

[Tony H]

There was one cylinder in compression stroke for over 20 years. The springs were not compressed. That might be the difference. I didn't think they lose strength, many engines are older than this one, but who knows?

That's what came to mind when I read it.

 

[zegersfarm]

Today I have tried to get the engine to reach operating temperature. The outside temperature was minus 5* Celcius. (23* Fahrenheit) I had the whole radiator covered and managed to get the temperature gauge up to 70 degrees Celcius, (158 * Fahrenheit) but the bottom of the radiator was still ice cold. The smoke was almost gone though. I am waiting until spring en then start using the tractor for fieldwork. I want to run it at full operating temperature.
BTW, I tested the compression after rebuilt with a 20 Bar gauge, an the needle went over the end of the scale for all 4 cylinders. I think the compression will be OK.