Your system has some changes or I don't understand the discription.
Standard basic liftall on a SM with engine pump used a 1 inch hose with 1 inch pipe threads from reservoir under fuel tank to the pump inlet for suction. 3/4 hose with 3/4 pipe threads was used from pump to reservoir for pressure. Inside the reservoir is valves to pressure the 3 openings on rear of the reservoir and are operated by the lever on the side of unit. moving lever all the way to rear pressures the 3 ports. Moving lever forward lets fluid come back through the same ports to lower implement. Only pressure to one side of a hydraulic cylinder can be used with standard liftall unit. Also a relief valve is located inside the liftall unit to keep system from overpressure.
To operate double acting hydraulic cylinders IH installed a double acting valve at the fill pipe location of the original belley liftall. Valve doesn't go to anything below housing. You may have this and is confusing the discribtion of unit.
IH put a tee in the pressure line and tied other opening of the tee to double acting valve inlet. Also they put a tee in the suction line and return oil from the double acting valve was returned to the reservoir or suction of the pump.
Reason for teeing in to the pressure line was so the relief valve in the liftall would still protect the system when the double acting valve was used. When no levers are engaged the pump just pumps the oil in a circle with no or very little pressure. To use the double acting valve the liftall lever was locked to rear with the little latch. Then oil pressure just circle through the two way valve until it was used to pressure a cylinder. If the liftall lever wasn't latched and pressure deadheaded the pressure would still circle through the liftall without pressuring the 2 way valve. If the liftall unit was to be used the double acting valve had a latch on it to keep oil from passing through so pressure would build on cylinders operated by the liftall.
To use a double acting valve and retain the IH relief valve you can tee into the pressure line and lock lever back or use a opening on the back of reservoir with lever locked back. Return oil from 2 way valve can be tied into the suction line or to fill opening of the reservoir. Less problem with blowing oil out if connected to the suction line. Its close but a 1 inch tee can be installed at the liftall suction port. This is long and hope its understandable. You may have something different or something changed over the years from what I decribed.
This post was edited by D Slater at 15:00:18 08/16/11.
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