1750 Gasoline, Compression Check

[Jon Wescott]

Tractor is not running right. A couple hundred hours ago it started out stalling out when under load and has gotten progressively worse until now it stalls out just pulling itself on level ground in 2nd gear. Rebuilt carb. Installed new distributor, plugs and wires. Set timing. Hooked up a smaller auxiliary gas tank and bypassed the fuel pump. Engine had a complete overhaul about 1500 hours ago, ran good for 1300 hours, but I'm out of ideas so I did a compression check. On any other tractors that I have compression checked, when I spin the engine 5 or 6 times the compression in that cylinder reaches its maximin pressure. On the 1750, gasoline, with the choke and throttle wide open, I had to spin the engine over 15 to 18 times before the compression gage climbed to it's peak for that cylinder. All cylinders measured 145 to 180 PSI. Do you know any reason it would take 15 to 18 revolutions for the pressure to reach it's peak. Thanks in advance for reading this long-winded post.

 

[scootergmc]

Assuming you did a dry compression test without a wet follow up?

Just spitballing, but since it progressively got worse and you've been able to tell, it makes me think something in the valvetrain got progressively worse until you just didn't have power anymore, (plus you've already isolated ignition and fuel). It would still run on 5 cylinders if it was an isolated cylinder problem.

Also, you've checked the intake for mouse/rat nests? It wouldn't be the first time they kept building a nest until a tractor didn't run.

 

[Tramway Guy]

Have you tried changing the coil? Will also behave like that.

 

[J.Wondergem]

Did you by chance do a vacuum check?

 

[Jon Wescott]

Thank you all for your suggestions. J. Wondergem = Did not do a vacuum check. My Oliver parts supplier could not get a replacement distributor with vacuum so I took what I could get. Tramway Guy =I have tried 2 or 3 different coils with no change in performance. Scooter =The intake is all clear, not even a mud dobber. I think your first thought was the correct one, " makes me think something in the valvetrain got progressively worse until you just didn't have power anymore". I did not want to get this deep into it because of removing a bolt on loader, sheet metal, fuel tank and fuel rack, and raising the cab in order to get the sheet metal off, but I went ahead and adjusted the valve lash. Most of them were about .005 to .010. Now it starts right up and revs up tight. I'll do another compression check to see if the adjustment made any difference and I will have to do some tweaking on the timing and carb, but I think the valve adjustment fixed it. OfCourse, the real test will be when I put it under load. Thanks again to all for your help.