I am working on a Toyota 5HBE20 S/N 10518 that has low hydraulic pressure. The pressure on lift with a small load is @ 500psi and stops lifting @ just under 900 psi and will not lift past the free lift cyl.. With a heavy load (3190#) it will never leave the ground. The battery is up and the voltage @ the motor is 35v on lift and drops to about 33v when it stops lifting. The pump was changed with no effect. I know the relief valve should be set for 2490 psi but it never gets even close. Thanks for any help you may offer