SMD compression

I"m still trying to figure out this miss and wondered what the compression should be on the gas side. I got a reading of 130, 105, 120, 115 with a somewhat questionable gauge. I got a reading of zero on all holes with the starting valves shut.

I read on here that if they were all above 80ish, they shouln"t be a problem. Does that sound about right?

My tractor has a fairly good miss/popping with whitish/blue puffs at anything above idle. I can"t tell if it is just on one cylinder, it sounds like it is random to me, but I"m not sure. This goes away going up a hill in 5th and becomes more pronounced going down a hill unloaded. I have moved the timing all around with no change.

Thanks for any help,
Dan

Why are you running it on the gas side? That's for starting only.

I was just checking the compression with the starter through the spark plug hole because I don"t have anything to check compression through the injector hole. I also wanted to verify the starting valve operation.

The miss/popping I am referring to is during diesel operation.

Thanks,
Dan

the second reading is a bit low. o reading with small valves closed is a good thing. diesel compression should be in neighbourhood of 450-500 psi. need a special adapter to check comp. through injector holes. may want to get injectors tested, to eliminate that department.

I would lay a dollar to a do nut that your miss is going to be something you do not want to find . If the miss is on the diesel side it will be either a cracked head of you have a crack in either 2 or 3 in the cylinder wall as this is where i have found most of the problems relating to misses on M D's thru 450 D's . If this is the case you can save your block by having it bored and a repair sleeve pressed in and rebored to take the standard sleeve . myself i love them old gas start diesels BUT HATE the cost of fixen them . They will run forever IF people would just learn not to shut them down HOT or stall them in the field and not be able to restart wright away . If ya want one to live ya warm them up slowly and when your done working them ya let them set and idle till the temp gauge is in the cold and shut them down ON DIESEL side not the gas side as the gas makes them hot again . Now it is possible that your miss could also come from the bushing in the injection pump being egg shaped as was the case with my 450 D as i learned a lot on that tractor many years ago . Back then i did not know much about repairing farm tractors and i bought this old tractor as is where is and it missed back fired and yes a diesel can back fire . BUt when ya put it under a load it ran fine when the load came off it started missing , Had a reg. I H mechanic come out one Saturday after noon and check it out and first words out of his mouth was cracked head . Back then a NEW bare head was 650 bucks from I H . My buddy and i tore into it and removed the head and set it off to be checked out and a valve job done . Well the head was GOOD and we put it back together and yep still missed . Next we swapped injectors from his 450 to mine and it still missed . Then we got brave and switched pumps now mine ran great and his missed , now we know it was the pump so off the pump went to be repaired . First guy wanted 650 bucks to rebuild as he told me that it needed this and that . Took it to the I H industrial dealer and he fixed it for 112.78 and made shell we say some IMPROVEMENTS to it like TD9 governor weights and spring cranked up the RPMs as far as he could installed a TD 14 plunger and showed me how to turn up or down the fuel for farming or pulling how to set the timing . From that day on that tractor never saw a stock pump setting and that was back in 69 . that 450 is still in my area and i have tried several times to get it back even tried to swap him out of it with a 706 D even up , all i get from the guy is Ain't noway as he clams it is the best tractor he has ever owned . And the only repairs done to it has been a injection pump rebuild For the same problem .So Check that out before taking the engine down first. Best place for getting that pump done is Progressive Diesel In New Castle Pa.

Sounds like timing, or injector not opening, if your getting lots of smoke on one cylinder it is very possible the starting valve in the head is not closing on that cylinder, you can take valve cover off to see if starting valves are closing all the way. I have seen this happen, and if valve is not warped, you can free up with kroil,pb blaster, they get carbon build up on stem, also check to see when you have compression lever in diesel mode that all starting valves are closing.

I have adjusted the timing from 16 BTDC to 4 degrees ATDC and the miss is still there. I think the starting valves are working correctly because I got a compression reading through the spark plug holes of 0 for all cylinders with the compression lever in diesel mode.

I cracked the injector bleeders and got squirts out of each one and each cylinder affected the idle. Not sure if they were all affected equally or not.

I did the same on my MD many years ago and got 110-120 as well. I did get a little pressure on one of my starting valves. That problem is probably resolved now after a complete head job this winter.