CA Hyd Pump Issue
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=18204
Printed Date: 06 Feb 2025 at 4:37pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: CA Hyd Pump Issue
Posted By: wkpoor
Subject: CA Hyd Pump Issue
Date Posted: 13 Sep 2010 at 7:21pm
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Something has been bugging me this summer ever since I got the tranny issue fixed in the real nice 52 CA. I don't remeber this when I first got it. Hard to explain but here goes:
In any mode if you leave the lever all the way back so pump will pressurize and send fluid to the rams, when it reaches approx 3400lbs ( I have a gauge plumbed in the remote) the system will unload like normal. Then if I stop momentarily with the foot clutch while leaving the lever back, and then release the clutch to move again I'm fighting the pump (which in some situations can actually keep the tractor from moving) to repressurize. Now here is the thing..... the gauge doesn't move but I suspect I'm only loosing 25-50lbs which won't show on a 5000lb gauge but just that little tiny bit is enough to try and force the pump to pressure the minute you start to release the clutch and thus fight the tractor to move. System is tight enough otherwise to hold plows or disc up all day in hold position or drawbar control. The problem is such that I often will disengage the PTO before I move again or put it in netrual to let out the clutch then emmediately put it in gear and go.
Is the check valve bad or is this normal ops? If it is bad then funny how it holds emplements. The reason I'm checking into this carefully is when I first got this (my first)CA I thought the pump was bad. The ratcheting pulses it makes when it pressurized made me think something was wrong. Everyone I talked to said they shouldn't do that. So I tore it down for a rebuild only to discover 4 pistons. Nothing was wrong at all! They have to do that because its a piston pump running at relatively low speed.
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Replies:
Posted By: Bill Long
Date Posted: 13 Sep 2010 at 9:09pm
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Just remember that the pump drive shaft turns at roughly pto speed 540 RPM. However, they put double cam lobes on it so the pump has two strokes per revolution.
May not help but that is one of the reasons I always told CA owners to let the pto stay in gear so the pump always ran. Otherwise, we would have stick plungers.
Good Luck!
Bill Long
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Posted By: CTuckerNWIL
Date Posted: 13 Sep 2010 at 9:19pm
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What you are describing is normal in my way of thinking. The pump unloads by making enough pressure to push a spring loaded plunger back enough to let oil seep by. As soon as you push the clutch in the bypass plunger closes with no leak down anywhere. When you let the clutch back out pressure in the pump most build up to move the bypass plunger back to the bypass position. That might only take a revolution of the pump cam shaft but is necessary and noticeable. I hope this is clearer than mud. Charlie ------------- http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF |
Posted By: wkpoor
Date Posted: 13 Sep 2010 at 10:44pm
Most of the time I'm not even close to enough engine RPM for 540 PTO cause I usually pull the throttle back before I disengage clutch. I don't like to sit still with the engine wound up. After I engage and get under way I throttle up for most tasks. The way I operate could be why its more noticeable to me.
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Bill Long wrote:Posted By: wkpoor
Date Posted: 13 Sep 2010 at 10:48pm
Tucker, I understand your theory and it makes sense. Before I go any further I'll try and drive another CA near me to settle in my mind this is normal ops. A freind of mine thinks it shouldn'd be normal as back when these were new no one would have settled for this quirk. Hard for me to say but there is some logic in his thinking also.
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Posted By: Brian Jasper co. Ia
Date Posted: 13 Sep 2010 at 10:49pm
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Normal operation, my CA does it too. Hydraulics/traction booster work fine on mine. I should add that I leave the pto in gear all the time so it stops the gears in the trans quickly for no grind shifts. ------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |