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jbrooks

New to me AC 920 diesel

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jbrooks

New Guy,  just joined .

Can't down load the manuals yet.

I dug out a AC 920 from last week, after sitting in the trees after 20 years of being sidelined.  Brought it home and started going through it. Took off the mower deck, and power washed it to remove the moss and dirt.  It appears to be all there, 1006 hours on the clock. looks like the original belts and blades on the mower deck and hardly any rust.  some loose flaky paint but 95% still good.

Pulled the injectors and put mystery oil in the cylinders. took the injectors apart and cleaned them.  The went overnight in evaporust,  they 4 hours in carburetor  cleaner, then couple hours in the ultrasonic cleaner.  A thorough rinse with spray choke cleaner between each process,  finally got the high pressure needle out after the first cycle in the ultrasonic.  reassembled them, purged the fuel with the manual pump until I got new fuel out the top fuel line.

Connected the injector lines, dropped in a battery and it started after 20-30. runs well, no leaks so far.  Changed the oil, cleaned the filter, new fuel filter, at it runs and goes.

 

The 920 seems to be complete and everything works,  has some broken wire issues but that's pretty easy.

 

Anyone else have a 920  I have a ton of questions

 

John Brooks

 

 

 

 

 

AC 920 2.JPG

Edited by jbrooks
added photo
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Talntedmrgreen

Welcome!  Sounds like you really jumped in...that's a great save.  The 920 (and sister Simplicity 7790) have long been venerable models in the Simplicity and Allis world.  They are very reliable and have oodles of power for any of the tasks a guy could put these thractors through. 

I had a 920 ages ago, and a few 7790's, my favorite of which I finally let go of a year or two back.

Simplicity 7790 Diesel with options - AllisChalmers Forum

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tadams

Welcome to the group, a $10.00 membership will give you access to the Manuals , there's tons of information on this sight and guys that can answer your questions. Tom

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jbrooks

Saturday update on the 920.  Took the deck apart stripped and repainted it. The bearings were all dry so I pierced the seal with a #55 drill  and filled them with molly B grease, all spin freely and with out noise.  I was surprised how well the original paint held up. Used a needle-scaler to clean the inside after pressure wash. It looked like it was rusted, turns out just still dirty, 95% of the orange paint was good. Used formic acid to convert any remaining rust, then the Rustoelum implement primer, and AC orange enamel top coat from Tractor Supply. Has the original AC belts and the deck looks new. I will replace the belts but the goal for now is get it mowing.

Removed the battery and fuel tank, then needle scaled and wire brush to the shelf and mounting supports. Paint was flaky and some rust from battery acid, but over all good. Got the same treatment as the deck, looks new in there now.

Started on the wiring, had several broken or bare wires behind the ignition switch. Looks like the switch is bad, a couple contacts open. The circuits are good, after my dues are processed I can see what is supposed to be there. I have just been tracing each wire backwards.  Oil pressure, head lights, fuel heater, starter solenoid all meter OK

Changed the trans fluid to Dextron VI had now have a seep on the right axle seal, but it progresses

 

 

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PhanDad
41 minutes ago, jbrooks said:

Started on the wiring, had several broken or bare wires behind the ignition switch. Looks like the switch is bad, a couple contacts open. The circuits are good, after my dues are processed I can see what is supposed to be there. I have just been tracing each wire backwards. 

Here's the wiring diagram for the Simplicity 7790 from the 1990 Simplicity Electrics Manual:

image.thumb.png.d045ee8eb16327e4a91ea076103a22d1.png

Shown above is the charging circuit wires used in bold.  

 

This diagram shows the safety circuit in bold:

image.thumb.png.15514f8078efa304052cfd2a1e61ed2f.png

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jbrooks

Sunday update.  Well the schematic made the wires easy. Got that done, installed a GP48 battery. It was 3/8" too long do I chopped of the toe clamps and its a press fit.  I think wth wire harnes goes  behind the steering column Seem to have some interference between the tank and harnes.  Oil pressure bulb is bad but swapped the ground to the fuel heater and it works. 

Couple more photos, it will cut grass tomorrow if the smoke clears. But it fires right up, PTOs work, no surprises yet.  Very will made

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Edited by jbrooks
Added left side photo. I don't think this has power steering. Just the lift
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MikeES

WOW!  Can't believe a tractor sitting in the weeds for 20 years can look that good.  I would have guessed it was stored inside a climate controlled room all those years.   And power steering to boot!

 

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PhanDad
35 minutes ago, MikeES said:

And power steering to boot!

The 7790 tractor with the “new style” PS is Josh’s. 
No pic of the left side of the 720, so can’t tell if it has the “old style” PS; the steering wheel is “manual” so it’s not the “new style” PS.  

 

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jbrooks

Well guys  its pretty much done for now.  Back together everything works, fires right up if you give it full throttle. I think that may be a diesel thing. But it cuts grass. and does what it is supposed  to do.  Was a fun project, can't wait to get to the documents and see what I missed. Got to use several of my "off color Italian hand gestures" figuring out the Lambardini  Diesel engine. Injectors are easy to clean and overhaul, still need to look at the Diesel Pump and adjustments.  But the old belts held up so far, all the PTOs work and it drives fine.  Will need tires, these are cracked from sitting flat, but green slime fixed the leaks, and with 15 pounds they are round. 

The wires had rubbed on the steering column and there were 5 or 6  that were bare. Do not know much about the history, it came from a dealer in Maryland. The last owner died about 15 years ago.  I would assume it was sidelined because the battery would not hold a charge. The heavy wire to the Amp meter was bare to the steering column.  I repaired the wires and covered them with chaffing tubing and put piece on the shaft to there will be no more shorts.  I had an old group 45 battery, it was a little too large for the shelf.  But I cut off the toe clamps on the bottom and it is a press fit into the box.

But its done for now. May repaint the rest in the future but it looks OK and has a good patina for its age, Much easier than an old Porsche  Thanks for following this adventure

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jbrooks

Last photos, loading it up to take it to the other shop.  Cut my lawn in 4 minutes, so I don't need it here. Plus the people next door complained about the noise and smell. Go figure, you can't see 100 yards for the Forrest Fire smoke, and they can smell diesel. 

 

First big cut, works great, had the first failure,  fuel pump L brackes broke at the bolts. Easy weld all good

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Edited by jbrooks
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