I think this power steer system comprises of a p.s activator unit, an optical encoder, power steer contactor, and a pressure switch, optical encoder located just under steer wheel covers, activator unit located on bracket beside steering orbitrol unit, but from what you say that when ps contact pushed in the power steer motor runs it would sugest a lack of pressure being developed by pump or oil being returned to tank,
Test 1 system won't switch on,.With the key switch on short terminal 4 on activator to terminal 2 power steer contactor should run continually, this checks,
Line. 13 from activator to battery
Line3
Fuse 1
Key switch
Line10 power steer coil
Power steer coil
Contactor

Let me know how you get on. It dose say on my notes E/J 1.25 -3.00 XL

Regards Titus