990 Selectamatic - Tipping trailer lifting but not lowering

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mattmorgans
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Joined: Thu Jan 29, 2015 11:01 am
Location: Bristol

990 Selectamatic - Tipping trailer lifting but not lowering

Post by mattmorgans » Wed Oct 07, 2015 8:45 pm

Hi All,

I have recently bought a 3 ton tipping trailer which I'm trying to use with my 990 Selectamatic. I've changed the hydraulic hose on the trailer from a screw on connector to a quick release in order to connect to the tractor. I'm not fully familiar with the hydraulic controls as it's been a bit trial and error to work everything out but there's a two way valve located to the left of the seat at elbow height which is connected to the rear hose for the trailer, a central hose runs to the four way selector below the two way valve and is set in position 2 (from the left). A further hose runs from the left of the two way valve to the loader control box on the right of the cab and is connected to one of the levers.

I am able to raise the trailer by pushing the lever on the two way valve to the forward position and when the lever is returned to the middle (neutral) position it stops but when I pull the lever to the rear position the trailer does not lower. I've tried all sorts of lever combinations but cannot get the trailer to lower.

Could anyone please offer any advice or help on what I'm missing or need to do to get the trailer to lower?

Many thanks in advance, Matt

JamesF
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Joined: Tue Mar 14, 2006 8:49 pm
Location: South Yorkshire

RE: 990 Selectamatic - Tipping trailer lifting but not lower

Post by JamesF » Wed Oct 07, 2015 9:44 pm

The trailer should tip when the lever is pulled back, hold in the middle and lower when pushed forwards

Guest

RE: 990 Selectamatic - Tipping trailer lifting but not lower

Post by Guest » Wed Oct 07, 2015 9:54 pm

By the description of the rather confusing plumbing it would seem that it would need to be returned to what it should be, the trailer tipping pipe plumbed into one of the side ports on the 3-way-valve, lever in position 2 from the left and the dial pointer to the right, 'external' position, it would then work. A few pictures of the current plumbing arrangement would help to see what's going on.

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erkki
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RE: 990 Selectamatic - Tipping trailer lifting but not lower

Post by erkki » Thu Oct 08, 2015 6:22 am

That kind of problem may occur because of un matching quick couplers. The spring in the trailers side is some stronger that on the tractors side and when tipping, oil pressure pushes the way open. When lowering, the pressure on the trailers side shuts down the way. That can happen when one side of the coupler is brand new and the other one old and tired or of another make. Just jumped into my mind.

W.B.R erkki

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DB780
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Post by DB780 » Thu Oct 08, 2015 8:32 am

erkki is correct but also not all male and female couplings are compatible with each other and has powerrabbit notes your description is confusing. Are you using the lever that operates the lift arms to tip the trailer or a double acting valve?

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mattmorgans
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Location: Bristol

Post by mattmorgans » Thu Oct 08, 2015 8:13 pm

Hi All,

Thanks for the input. I've added a few photos I've taken and annotated which hopefully will help. I've also replaced the hose from the two way valve to the female quick release for the trailer so they are both new couplers but have tested and trailer still only lifting and not lowering. Another thought is could I bypass the two way valve and connect the trailer up to the spare loader control...see pic?
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Guest

Post by Guest » Thu Oct 08, 2015 9:01 pm

Still a very confusing spider web of hoses. Seems to me like the valve with the handle/knob is not allowing the oil to return, you need to try and plumb a separate hose into the 3-way-valve in the top port, picture 3, connect the trailer tipping pipe to it, move the 3-way-valve handle to open this port, put the dial pointer in the 'external' position, pushing the lift lever back into 'select' at the same time and see if the trailer tips when pulling the lift lever back all the way against the spring in 'select' again, you have to hold the lever back for the trailer to tip, if it does, then lower the lift lever to two thirds the way forward in the quadrant and twist and pull up the dump valve, upright handle just behind the rear of the quadrant, the trailer should then down again. Try this and see if it does, if not then you will probably have to completely re-plumb everything and use the constant pump method.

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case-ih1594
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Location: Preston

Post by case-ih1594 » Thu Oct 08, 2015 10:57 pm

Hi, sorry I have just scanned tot he end, but I used to work at a farm where the DB 880 had a similar valve fitted because the Selectamtic control valve had broken (or bunged up) probably due to lack of servicing of any kind. A few months later their 885 did the same.

Anyway, the set up on this tractor MAY be the same. If this is the case, the operation of the main quadrant lever would have no effect. The pump was pumping fine, but it was an 'all or nothing' conversion.

John_Allen
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Location: Cumbria UK

Post by John_Allen » Thu Oct 08, 2015 11:50 pm

Just one point: the valve on the wing is a diverter valve, not a 2-way valve as such: it diverts the flow to either outlet and, when in the "neutral" position, stops flow altogether.

I would suggest that you have a "catch" on the lift lever (on RH side of the seat) and that the hydraulics are continuously pumping - this is so that the oil is always flowing through the loader valve: the loader wouldn't work otherwise. If you take the catch off the main lift lever, move the lever forwards, the trailer will lower.

The more sensible way of doing things would be to take the diverter valve off, connect the tipper pipe to port 1 of the 3-way valve and the loader pipe to port 2. This is the normal way of fitting a loader and tipper pipe.

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mattmorgans
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Location: Bristol

Post by mattmorgans » Fri Oct 09, 2015 5:16 pm

Update: I've just borrowed a hose from my local Lister Wilder guys and connected it to the spare port on the loader control and the other end to the trailer. It now lifts and lowers (lifting is a reasonable speed but lowering is a lot slower). So have bypassed that confusing two way valve and now working, thanks for all your input and now starting to get my head round some of the hydraulics.

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