Smoking diesel mystery

[stso9d]

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

Google results state that white smoke is most likely unburned fuel. There is a good article on producer.com about this.

 

[Bentrim]

White smoke is usually unburned fuel caused by low compression, a "cold" engine, bad injectors, injection pump out of time. In your post you stated you covered the radiator and once the engine temperature went up the smoke just about disappeared. Is there a thermostat in the engine? Is it functioning properly? Also have you rechecked the injection pump timing?
From what I have read of the posts I would be inclined to believe it is too cold. Most diesels do best running on the warmer side.

 

[finn1]

White smoke is generally associated with low compression, retarded injection timing, or low cetane fuel.

 

[DutchInNZ]

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 a 5745 and done about the same job as you did, although mine was not seized It definitely is surprising that you can compress valve springs by hand. Remind me to never shake hands if we meet. Why don't you try and compare that with your 8011?

When compression testing, the rpm's are low, so even weak springs have enough time to close the valves and therefore you will see a high compression. When the engine is running, the springs may be too weak to push the valves back in time for the higher rpm's so you don't reach that high compression. The valve play seems to be correct; otherwise you would not get such high compression figures.

Some thoughts. The pick-up of the thermostat is located in the cooling exhaust of cylinder 4, immediately behind the cylinder head. If you get a running temperature of 70C or even less, that can have two causes; one: the thermostat is not closing (here less likely, if I read what you said about the radiator), and two: there is no or hardly any combustion in that cylinder. The UR1's do not have glow plugs, so because of incomplete combustion they smoke a lot while they are cold. Combine that smoking effect with the low temperature and the weak valve springs, I agree with those that blame the springs. Weak springs -> loss of compression -> incomplete combustion -> cold and smoke. You most probably will be missing a lot of the 70 horses that should come out of those 3.6 litres.

I have the parts catalogue with exploded views, the Zetor workshop manual, the user manual, oils info and electrics for the UR1; together it is abt. 250MB. If you want a copy, send me a mail. Parts come from BENO s.r.o. Zetor ZTS Martin díly - parts, a reliable supplier that don't charge you your last shirt. As you are outside of the EU, you can take the tax-free prices.

 

[DutchInNZ]

One more thought: if the engine runs, the inlet springs seem to be OK; otherwise it would blow back hard into the inlet. From the picture it seems that only the outlet springs are weak and springs do not go weak from being compressed. A botched up repair job and therefore the reason to ditch it so long ago?

 

[sd455dan]

My 2 cents
If the ring gap is good I would suspect the valve grinding/ seat grinding being suspect. I still need to eventually pull my rhino apart because I hired a shop to do a Valve/head job. I had 1 slightly smoky cylinder. I Replaced rings and even the liner for the smoking cylinder. Had the head off twice.

The shop would not show me their seat grinding equipment. After I put the engine back together and still had smoke on the one cylinder...
Turns out they didn't have a seat grinder...
The so called machinist eventually admitted all he did was grind the brand new valves I gave him and then lap them into the seats by hand.

Told the guy you were paid to do the head.

He said emphatically I did a "Valve" job.

Still ticked.


I bought my own valve and seat grinding equipment. Just have to get the time and Fix Mr mechanics work.


ps. the smoky cylinder on my tractor has ~360psi cranking compression

A dead giveaway that it is valve seat seal on my tractor is when a light fluffy snow falls around the air cleaner intake, it will blow the snowflakes away in a pulsing fashion in the right conditions. I also fired the tractor up at night with no exhaust manifold. flames escaping by the exhaust valve and seat on the same cylinder.

 

[etpm]

Properly lapped valves will seal just fine. But a good grind on a valve which is then lapped into a head will often not fix the bad valve seat in the head. And will also ruin the grind on the valve. So paying attention to both the valve and the valve seat will help insure that your valve(s) seat properly, both cold and hot. There is nothing wrong with lapping a valve into a head after both the valve and valve seat have been ground and/or cut. But the amount of material removed is miniscule and the lapping process should take very little time. You cannot count on lapping to fix bad grinds or grinds done to different angles. It's too bad your "machinist" did not understand this.
Eric

 

[pmsmechanic]

Just an fyi. On every diesel engine that I have ever bothered to check, you can compress both the intake and exhaust valves by hand. You don't need a lot of strength either. Just push down on the valve with the heal of your hand.

I'm also in the camp that thinks the problem is the thermostat. That engine needs to run at 90C/195F or more to properly atomize all the fuel. Good idea to close off the whole radiator to try and get the temps up.

 

[sd455dan]

Properly lapped valves will seal just fine. But a good grind on a valve which is then lapped into a head will often not fix the bad valve seat in the head. And will also ruin the grind on the valve. So paying attention to both the valve and the valve seat will help insure that your valve(s) seat properly, both cold and hot. There is nothing wrong with lapping a valve into a head after both the valve and valve seat have been ground and/or cut. But the amount of material removed is miniscule and the lapping process should take very little time. You cannot count on lapping to fix bad grinds or grinds done to different angles. It's too bad your "machinist" did not understand this.
Eric

No argument except to state I Knew that cylinder had a problem because the intake gasket apparently moved when the tractor was originally built so for the 1st 15 years it was eating dirt that did not get trapped by an air filter dusting the cylinder and damaging the seats and valves on that cylinder.

When a seat is damaged/worn no amount of lapping is going to make the seat concentric and lapping wont allow the seat width to be corrected once worn , That also requires grinding to the correct width by using the different angles to set the seat contact area on the correct part of the valve face.
No argument on lapping as a final touch either.

 

[etpm]

No argument except to state I Knew that cylinder had a problem because the intake gasket apparently moved when the tractor was originally built so for the 1st 15 years it was eating dirt that did not get trapped by an air filter dusting the cylinder and damaging the seats and valves on that cylinder.

When a seat is damaged/worn no amount of lapping is going to make the seat concentric and lapping wont allow the seat width to be corrected once worn , That also requires grinding to the correct width by using the different angles to set the seat contact area on the correct part of the valve face.
No argument on lapping as a final touch either.

That's what I was saying. Lapping is only for perfecting a properly machined or ground valve and seat.
Eric