not running on all cylinders

[colonel1958]

oliver super 88. replaced coil, cleaned carb,new plugs, wires are one year old. i am getting spark to all cylinders,rev it up sounds like one cylinder isn't working doesn't have full power. motor idles fine. underload you can hear it running on 5 cylinders. any help greatly appreciated.

 

[Jim.ME]

oliver super 88. replaced coil, cleaned carb,new plugs, wires are one year old. i am getting spark to all cylinders,rev it up sounds like one cylinder isn't working doesn't have full power. motor idles fine. underload you can hear it running on 5 cylinders. any help greatly appreciated.

Time to do a compression test?

When was the last time you adjusted the valves?

 

[RedRamGT]

You might check the ignition timing, to see if the advance is not working right at higher RPM's.

 

[used red MN]

Maybe a worthless test for the non mechanically astute. Pull the coil wire and crank the engine. An engine with a cylinder down on compression will crank uneven as when the weak cylinder has its turn to build compression it puts less resistance against the crank throw and the starter speeds up. It really tells you nothing more than there is a likely problem in one of the cylinders that will be shown in a compression test.

 

[Charlie M]

Was it doing all stuff you say before the tune up or started after? I'd double check the spark plug wires are in the correct position and then the other stuff already mentioned. I's also check intake manifold for a suction leak due to a rust hole.

 

[T.R.K.]

If it was o.k. before the tune up, I would pull the spark plug wires one by one and see which cylinder was the one by noting which cylinder didn't cause a drop in rpm.
I had a Moline U once that did that, it turned out that a place on the valve seat had eroded. It is also not unheard of to get a bad spark plug-one that shorts rather than fires the electrodes.

 

[rustred]

oliver super 88. replaced coil, cleaned carb,new plugs, wires are one year old. i am getting spark to all cylinders,rev it up sounds like one cylinder isn't working doesn't have full power. motor idles fine. underload you can hear it running on 5 cylinders. any help greatly appreciated.

A Compression test will tell u
More than anyone here can. Check it and post back weigh your results. It’s part of a tune up.

 

[used red MN]

It is also not unheard of to get a bad spark plug-one that shorts rather than fires the electrodes.

Probably goes without saying, I would also recommend double checking the plugs for a proper gap.

 

[rustred]

Probably goes without saying, I would also recommend double checking the plugs for a proper gap.

And when he pulls them plugs out it will show which one is not firing.

 

[jimg.allentown]

You might check the ignition timing, to see if the advance is not working right at higher RPM's.

Timing problems will affect ALL cylinders - not just one.
In this case, missing on one, checking advance would be a waste of time. A compression test would be far more useful.

 

[colonel1958]

A Compression test will tell u
More than anyone here can. Check it and post back weigh your results. It’s part of a tune up.

compression, 145 -150 thru all cylinders

 

[colonel1958]

Was it doing all stuff you say before the tune up or started after? I'd double check the spark plug wires are in the correct position and then the other stuff already mentioned. I's also check intake manifold for a suction leak due to a rust hole.

 

[colonel1958]

did all the above

 

[BarnyardEngineering]

did all the above

Pull plug wires one at a time and listen for a change in how the tractor runs. When you pull the wire that doesn't change how it runs, you've found the cylinder that is not firing. Concentrate your efforts there.

If you cannot find one particular cylinder that is dead, check the shaft in your distributor. If the bushings are badly worn and the shaft is flopping around, it will misfire randomly.

 

[countryman]

Pull one plug wire at a time and notice a power drop, the one that has no change is the bad boy.

 

[560Dennis]

https://www.harborfreight.com/media/catalog/product/cache/c7f358f04aec81e7c5e0be4c56edf041/6/3/63985_W6.jpg?auto=webp&width=1200&height=1200&canvas=1200,1200&fit=bounds

These thermometer can give you the location of cold cylinders.

 

[jimg.allentown]

did all the above

My opinion would be that you have a bad plug that is breaking down under load. Maybe one has a cracked porcelain insulator that fires OK at low loading and gets worse as you apply load.

 

[used red MN]

compression, 145 -150 thru all cylinders

A weak valve spring can show good compression but drop the cylinders pumping ability at higher speeds.

 

[rrlund]

oliver super 88. replaced coil, cleaned carb,new plugs, wires are one year old. i am getting spark to all cylinders,rev it up sounds like one cylinder isn't working doesn't have full power. motor idles fine. underload you can hear it running on 5 cylinders. any help greatly appreciated.

Have you pulled the wires out of the cap? My 77 was acting up. When I pulled the wires out, one was corroded so bad that it pulled right apart, the end came right off. Spark could have been getting through it but jumped all over at higher rpms.

 

[560Dennis]

Checked the fuel flow ?

https://forums.yesterdaystractors.com/pages/artint13/

This is in resources articles help