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jdlx173
Join Date: Nov 2004
Posts: 12 western ny
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2004-11-05          99880

I have a question for you guys. My brother in law has a Ford 3000, 3 cylinder tractor. What's the compression supposed to be? I did a compression test on it and got about 25 pounds per cylinder. I know my John Deere 420 gets about 100 pds. I can't get the Ford started. I rebuilt the carb and all the electical and to no avail. It still doesn't start. I think there's somthing wrong in the engine but my brother in law doesn't think so. So any imput would be appreciated. Sorry for bringing a Ford into the John Deere forum.

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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2004-11-05          99881

Bare minumum to get that engine running would be more then double then what you are saying you have. I figure that it is a gas engine, and they will often run with lower compression then the 120 to 130 that they are supposed to have but you will have little power. ....

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jdlx173
Join Date: Nov 2004
Posts: 12 western ny
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2004-11-05          99884

Yes it's a gas engine, I should of clarified that. What would be the minimum comp. be for it to start? ....

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denwood
Join Date: Jul 2004
Posts: 542 Quarryville PA
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2004-11-05          99885

I was told near 100 psi is necessary to run. you may try adding a little oil to moisten cylinders and boost it, rings may be stuck and dry. I doubt oil will boost the numbers you are getting enough to run. ....

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Billy
Join Date: Oct 1999
Posts: 975 Southeast Oklahoma
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2004-11-05          99886

You ain't gonna get it started with that amount of compression. If this is the gas engine, you need at the very least 50 lbs of compression. Even at that, you'd have to spin the engine pretty fast to get it started. Then you won't have much power.

Sounds like this tractor has set a long while? If so, sounds like the rings are stuck. ....

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2004-11-05          99887

JD, as Art stated, I doubt you could get an engine to light up with anything less than 50 psi as a bare minimum.

Any clue as to the background of that beast? I can't believe it got worn to the point of 25 psi in all 3 cylinders. In fact with compresssion that low I'd be wondering about a mechanical problem, any chance it got frozen and that opened the cylinders or something like that?

Best of luck. ....

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jdlx173
Join Date: Nov 2004
Posts: 12 western ny
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2004-11-05          99888

Thanks for the imfo. I'll try it and see what happens. What would be the next thing to do if that doesn't work . I thought about popping the head to see if the head gasket is blown but than wouldn't I get more compression on one of the other cylinders? ....

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jdlx173
Join Date: Nov 2004
Posts: 12 western ny
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2004-11-05          99889

Yes the tractor does sit outside during the winter, But I been getting it to run for the past several years un til this year. so maybe you guys have a point that there's a intermal problem. ....

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Billy
Join Date: Oct 1999
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2004-11-05          99892

Since all 3 cylinders have the same reading, I'd go with stuck rings. Course it could be valves not seating but pouring oil in the cylinders (if the compression comes up drastically) would rule the valve problem out.

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jdlx173
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Posts: 12 western ny
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2004-11-05          99894

Thanks for the heads up. I'll try it and see what happens. ....

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BillMullens
Join Date: Jun 2000
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2004-11-05          99903

In my experience, even stuck rings wouldn't lower the compression that much. Remember that each piston has 2-3 compression rings plus an oil control ring; to get compression that low, you'd just about have to have all of them broken or stuck.

I think stuck valves are much more common; as the engines get older, they burn more oil, and carbon creeps up the exhaust valve until it interferes with the valve guide and the valve is stuck open. No solution but to remove the head and fix it. Now, sometimes valves will get a piece of carbon or rust stuck on the stem, and you can take the valve cover off and work the valve up and down manually to get it freed up. My Farmall A did that when it set for a few months when it was being restored.

Billy, I think it is the other way around on a compression test; if a tablespoon of oil raises compression dramatically, it points to the rings being the culprit.

Good luck,

Bill

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Billy
Join Date: Oct 1999
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2004-11-05          99929

Bill

"Billy, I think it is the other way around on a compression test; if a tablespoon of oil raises compression dramatically, it points to the rings being the culprit."

I thought that's what I said. :)

"Since all 3 cylinders have the same reading, I'd go with stuck rings. Course it could be valves not seating but pouring oil in the cylinders (if the compression comes up drastically) would rule the valve problem out."

Either the rings or valves but either way, it's hard to imagine all 3 cylinders having the same low compression.
....

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Art White
Join Date: Jan 2000
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2004-11-05          99931

Take the compresion again only this time have a oil can with any oil you would like. The thicker the better, just a few squirts about five at max. Take the copmpresion right after oil is put in. If it raises the compression then it is the rings. If it doesn't change then it would be he valves. ....

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drh1983
Join Date: Feb 2004
Posts: 20 Cedar Rapids Ia
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2004-11-05          99933

A jumped timing chain or gear could also give low compression, you can check that with a timing light.
Also double check your compression tester. One time
I replaced the valve core in my compression tester with
a core from a tire valve stem, compression would only
read 25psi (core spring too strong) I bought the correct
valve core from the Snap-On tool man... ....

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jdlx173
Join Date: Nov 2004
Posts: 12 western ny
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2004-11-06          99942

Thanx guys for the help. I will give it a try. Thanks again. JD. ....

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BillMullens
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2004-11-06          99976

Ooops. Sorry Billy. I read that wrong the first time.

The likely scenario for a high hour tractor is one cylinder gets worn, has broken, worn or stuck rings, or stuck valves, and although it isn't running right, the engine will still run and the user doesn't notice because it is a gradual progression (or digression). As the hours pile up, another cylinder starts to go, at this point it still may start and run and still be useful. Finally the last cylinder gets bad enough that the tractor either smokes excessively, uses a lot of oil, won't pull what it is supposed to, or won't start. Then it seems to the user that it got bad all of a sudden when it really had been coming for a while.

I'm rebuilding a '52 Super C. Just today, I bolted the head back on and noticed one of the valves wasn't closing completely. Even then, it was showing about 50 psi on that cylinder (cranking by hand). I'm not sure how an engine could show as low as 25 psi. Make sure the throttle is open completely and crank until the gauge doesn't progress.

Just my thoughts.

Good luck,
Bill

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