This is the first post in what will probably be a very slowly progressing project to replace the stock serpentine belt driven power steering pump with an electric motor driven power steering pump. I have done a fair amount of research on the internet regarding converting various vehicle's hydraulically assisted rack and pinion steering from a belt driven pump to an electric motor driven pump. Some conversions were to achieve space near the front of the engine for a supercharger. Others were to reduce engine loss for drag racing. Some were to improve the performance and handling for circle track or road coarse racing. Most were for gas to electric powered vehicle conversions. There are two types of electric motor power steering assist. One type is an electric motor with shaft and gearing integrated into the steering column that assists the driver in turning the steering shaft. This is the latest technology because it saves power and reduces fuel consumption. Unfortunately, when the system fails the vehicle is nearly impossible to drive. It would also be impractical to retrofit to my Explorer. The other type replaces the belt driven pump that pressurizes power steering fluid to the steering rack with an integrated electric motor driven pump to perform the same function. This configuration is much easier to retrofit and consequently used electro-hydraulic pumps are in high demand. The only electro-hydraulic pump I found suitable for retrofit on my Sport was used on the early 1991 thru 1995 Toyota MR2 - a mid engine sports car hence no belt driven pump. This particular series has no integrated power steering reservoir allowing it to be short enough (hopefully) to fit under the battery tray. I have seen these used units sold on eBay for $400 and new ones cost over $800. Last night one was advertised with a purchase now price of $90 and I bought it with no hesitation. I have an electronic copy of the 1991 MR2 wiring diagram which shows several other power steering related electrical components: ECU, relay, power driver module. These are also expensive to purchase and difficult to find. However, the pump will run at full speed continuously with just power applied to 2 pins. The other components reduce the power consumption (up to 80 amps at startup under load) and vary the pump rotation speed for more assist at slow vehicle speeds and less assist at fast vehicle speeds. Many of the later generations have a steering angle sensor (SAS) that increases pump speed when the steering wheel is turned faster. My Tahoe had variable assist power steering with an SAS on the steering column. As it aged the sliding contact surface became coated making the contact unreliable. On occassion when the wheel was turned at 30 mph the power assist would go to full eliminating all steering wheel turning resistance. If I was not quick to respond the vehicle would unsafely oversteer. After I figured out what was going on I periodically cleaned the contacts by spraying with electrical contact cleaner. I doubt I will purchase any of the other MR2 steering components. I will probably purchase or design and build a high current motor speed controller that uses the Explorer vehicle speed sensor output (same signal that controls radio volume) to vary the power steering motor speed. Instead of a fuse for the motor power I will use an automatically resetting circuit breaker. I will also need a small reservoir and space to locate it as well as a high pressure hose going from the pump output to the steering rack.