Super MD that misses

[Gerald Culverwell]

I have a SMD Farmall that missfires on #4. The injectors are good, head has been reworked, it runs excellent on the gas side. I am at wits end trying to make it fire.

 

[Anonymous-0]

sounds like the gas portion of the combustion chamber is not sealing off when you switch to diesel, keeping the compression too low for compression ignition. Leaky valve, tight valve etc.

 

[Doc Larry]

I agree with Jon. I'd check the starter valve on # 4 to see if it might be stuck in the open position. Seems to happen quite often.

Larry

 

[Jim J]

I bought a SMD that ran good on gas and missed on diesel and one of the sleeves was in pieces in the oil pan

 

[the tractor vet]

If ya have a miss in and old gas start diesel and ya say that the head has been redone then ya had best be looken for a crack in the sleeve along with a crack in the block, the crack will run up and down between three and four . Most of the ones that i have found have been between two and three but have found them on other cylinders. Drove me and a buddy plum nuts tryen to find the miss on his MD as we had two missen one bad miss on three and a slight miss on 2 . End up boring the block and pressen in repair sleeves and reboring for the std. sleeves . YA got to remember just how old these engines are and how many times that they have been heated up and cooled down and Stress cracks start . It is it's way of relieving it's self.

 

[Janicholson]

The others might be correct, I'll add a quick check of th e#4 start valve. Pull out the #4 sparkplug and pull the tractor in Diesel Mode (even with the fuel shut off) if the valve is stuck, that compression comming out of the spark plug hole will make a lot of racket. JimN

 

[Gerald Culverwell]

I checked about the starting valves and no problem there. I also put about a cup of diesel on the pistons when the head was off and was very little seeped by.