I'm at a loss so I don't know where to turn. I swapped in a 5.0 after my son blew the 2.9 that was in it. I took the engine and accessories from a 97 exploder. Everything went in ok, it runs with no issues. The only issue i'm having is the power steering doesn't work. The 97 pump was used since the accessories are bolted to one unit. The pump just doesn't seem to be pushing much fluid. I'm using the stock box on the ranger. Is there a pressure differential between the pump for a box and a pump for a rack? I've changed the pump twice, removed and disassembled the box to make sure that nothing was broken but still no PS. I'm about rdy to screw the whole thing and put a manual box on it and call it a day. Others whom have done the swap say they didn't have any problems but I'm stuck. It is really undriveable at this point. Any help would be appreciated. Thank you!

 

With the engine at idle, you should be able to hear/feel the load of the pump as you move the steering wheel from side to side a little bit. Almost like wiggling it back and forth.
If the pump doesn't load up, then either 1)the pump doesn't work or 2) the spool valve is not opening to put pressure on one side of the piston or 3)the box has a lot of leakage internally.
The pumps are pretty simple. If there was a blockage from the reservoir or return, you'd get some noise pretty quickly as the pump rollers ran dry.
The box you have had apart, so know what's inside. Did you check that the spool valve works in both directions, and opens up?
One last ignorant thought is does the pump rotate in the correct direction? I know some water pumps rotate counter to normal, and wonder if the exploder may have a ps pump rotation difference.
Last question, are the two hoses, high and low, made up with different size fittings at both ends such that they cannot get installed criss-crossed or backwards? Did have a Jeep that was equipped with a hydraulic fan motor run by the PS pump. Had intermittent power assist, and that only at high rpms. The fan motor was broken and allowed fluid to flow through freely, not turning the fan, and mis-directing all the pump output to circulating the fluid. Dealer finally found that one.
If you do not have access to gauges (who does?) you should be able to note the high side line 'flex' as the pressure rises and falls. If it does nothing, either there's no back pressure (the fluid should be flowing like crazy inside the reservoir) or there's no pressure being developed. Did the old box have any sort of 'morning sickness' that required it to get warm before having assist?
tom

 

No there was no morning sickness in the old box. The steering worked just fine until the engine blew. Ever since I did the swap I haven't had any PS. The worm gear in the box works. I have no idea where the valve is as I only had the big parts out and cleaned. The pump just doesn't seem to pump much fluid back into the pump res. My guess is, with the 4" lift and the Explorer tires I put on it, that pump just doesn't push enough fluid.

 

The gizzards of the box use a shaft that will twist for the first few degrees of travel before you get 'mechanical'(non-power) steering. The shaft being weak will not move the spool valve open until you have applied more force, as it will not twist enough strongly to open the spool valve. A stiffer shaft will twist the spool valve open sooner, thus applying power at the first motion of the steering wheel.
If you had good power assist before, did you have the same tires and lift installed? If so, swap in an equivalent pump. If not, you'll have to get one that produces more volume and/or pressure. Check the diameter of the pulley also as that will affect when the pump produces. If you have a large pulley, try swapping for a smaller diameter to bump the pump revolutions and in turn, output.
tom

 

I had a completely working PS system before the swap. I did a 4" lift and put 235/75x15 tires on it, it came with 205/75x14. I did this at the same time as the engine swap. Since the pump came off a rack, and a rack requires less flow/pressure to operate it, im going to get the old ranger pump or see if I can find a Saginaw pump. The trick is then to find the correct spacing.