Starts and runs fine on gas, will not run on diesel, tons of white smoke. Pump pressure is in the operating zone. Drained fuel filters and cleaned out diesel sediment bowl. Opened injector bleeders, all have fuel pumping out. Intake and exhaust valves are opening and closing. Gas intake butterflies are opening and closing. Been a good running tractor for 30 years, any suggestions? Thanks Z/
- Thread starter Z/
- Start date
With the valve cover off, you can readily see them, they have a cup over the end and just put some penetrating oil or any oil and try to tap them up and down. You may have to go through the spark plug hole to try to gently push them up. Worst case, take head off if stuck. Can be fun.
Lloyd Sorlien
Member
sounds like maybe a cracked head and getting water in cylinders. They are noted for cracked heads.
Mr. Pete
You were right, have compression in all 4 cylinders with switch lever in Diesel. Where do these valves open into? Up or down? Does the cap over them in the valve cover come off? Are they shaped like a regular valve? Can they be accessed through the intake and exhaust openings? Does anyone have a diagram of a Diesel head? Does anyone have manifold gaskets? Thanks Z/
You were right, have compression in all 4 cylinders with switch lever in Diesel. Where do these valves open into? Up or down? Does the cap over them in the valve cover come off? Are they shaped like a regular valve? Can they be accessed through the intake and exhaust openings? Does anyone have a diagram of a Diesel head? Does anyone have manifold gaskets? Thanks Z/
The cap or cup over end of valve is pushed down with the decompression mechanism and is under neath the rocker arm shaft. If you wanted to take the cup off you would have to remove whole rocker arm assembly. They are a regular shaped valve but very small, and open into the spark plug, gasoline side combustion chamber therefore lowering the compression ratio for starting on gas. Usually you can get them to move down a little but getting them to move back up is a little harder. You might be lucky and be able to do so from spark plug hole but those two center ones are really hard to get at. May have to take manifold off. They have to move totally free and also not leak when seated. They are very prone to warping when not cooled on their seats. That is why I suggest checking by cranking with spark plugs removed with lever in diesel position as first of all if stuck open you will have total compression leaking out through the plug hole and if they are closed but leaking you will have some leaking. A slight leak can be tollerated .There are other ways to also check them but this is simplest.
First off, I shut my MD down on gas every single time. After I started reading YT I tried shutting down on diesel a couple times and the tractor wouldn't restart for crap. My guess is too much fuel oil in the cyls to get things going on gas. I shut it down on gas (like the book says) and then put the lever in diesel when it turns off.
I would pull the valve cover next and investigate a little more. That is odd that all four would stick down. How long was it sitting? Are you sure the lever is in the correct position?
I would pull the valve cover next and investigate a little more. That is odd that all four would stick down. How long was it sitting? Are you sure the lever is in the correct position?
The cups don't travel down below the surface of the head. They are there to provide even pressure on the top of the valves since they do not use a standard push rod setup.
The cups/valves get pushed down about .75-1" when the lever is pushed.
If you pop the valve cover you can see all of this stuff right there in front of you. You can then pull/push the decompression lever and see how it is functioning and compare it to how it should function. You could also take a look at the parts diagram (go to the CNH website and navigate from there) The diagram may help you see how everything in there works. I never fully comprehended everything that happened to go from gas to diesel until I took my valve cover/head off and watched it all happen.
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