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Electric power steering pump

Discussion in 'Modified 1995-2001 Explorers' started by 2000StreetRod, April 30, 2012.

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    1. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      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.
      MR2SteeringPump.jpg

      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.
       
      Last edited: December 2, 2012
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    3. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      big and heavy

      The electric power steering pump/motor is bigger and heavier than I realized.
      MR2Pump.jpg
      It is about 11 inches tall and 6 inches wide. It weighs a little more than 11 pounds. It will be challenging to find a place to mount it. I'll pull my wheels to change my spark plugs soon and see how much space is under the battery support shelf.

      Even though I don't plan to use the ECU that controls the power steering pump I ended up with one because nobody outbid my $11 offer.
      MR2PumpECU.jpg
      I would need the associated driver module to use the ECU and I suspect a 100 amp motor speed controller might result in a simpler system to implement.
      100AmpControl.jpg
      I haven't found one from a U.S. supplier yet.
       
    4. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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      This is interesting since I didn't know that any vehicles used this set up at that time. Many years ago I fabricated my own electric steering set up in my 1988 van using a Dayton hydraulic pump, and several parts that I had to design myself. It has a magnetic reed switch near the steering column with magnets strapped to the column shaft. I had to design the control module since there wasn't anything readily available. The first module wasn't as good since the pump would run too much. The second module was very complicated, and took 5 months to design. The pump's brushes wear out occasionally, and the starter solenoid wears out often since the pump requires a lot of current to run. I had to install a second battery with an isolator, and a high current alternator to compensate.
       
    5. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      variable speed?

      I assume that the reed switches detect steering column movement to activate the pump motor. That's a good way to save energy consumption. Does the system respond quickly? Does your controller vary the motor speed?

      I plan to have my pump run continuously but eventually vary the pump speed based on vehicle speed. From what I've learned the motor start current is much larger than the running current. Also, the current draw is proportional to load. Hopefully, once the hydraulic system is pressurized the current draw will be less than 20 amps except for low speed turning.

      P=E*I (13v*20a= 260 watts) HP=260/745.7= 0.35

      What is the rating of your pump motor?
       
    6. CDW6212R

      CDW6212R Elite Explorer

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      Interesting Dale, I'm watching.

      I wonder how well an electric fan controller might function to power that pump. I'd contact Brian of DCC to ask for his input. I wonder if a pressure sensor in the PS line could be used to help to demand more current for the "system."

      Find out what kind of PS pressure there is in the OEM lines in various places, with and without the PS pump running. Maybe a simple sensor etc, may be used with a DCC device to power that electric PS pump.:scratch:
       
    7. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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      It only uses one reed switch, but it has several magnets on the shaft. The switch could trigger the controller by either opening the contact when the wheel is moved or closing the contact when the wheel is moved. The pump isn't variable speed. Since the magnets are powerful, and spaced very close to each other, it only requires a slight movement to activate the system. I bought it from Grainger in the early 1990s, and might have the box with the part number in my shed or basement somewhere. I tried using the original power steering pressure switch to trigger the pump, but was unsuccessful since it was wired to the computer. Ford uses a real ground, and a virtual ground for the sensors. The computer in the vehicle will get damaged if you try to make the virtual ground into a real ground. I had to replace the as a result, so I speak from experience. Since your model doesn't have the sensor or the PCM wiring, you could remove the factory plug, and connect a sensor from Autozone. They are around $7 or more.
       
    8. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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    9. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      no progress

      Thanks for the information and the interest. Unfortunately, family obligations (disposing of my mother's estate) has prevented me from pursuing any automotive activities (except the forum) and likely will continue for several more months. I'm beginning to experience automotive project withdrawal.
       
    10. CDW6212R

      CDW6212R Elite Explorer

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      Take care there Dale, I understand about the family issues. Stay warm etc, with this winter weather.
       
    11. Flash

      Flash Well-Known Member

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      I'm sorry to hear about your mother.

      I don't have any issues with the current steering set up in my Exp but this might be a good idea for my BMW.
      I've had an Eaton M90 sitting in the garage supercharging a shelf for a while now while I figure out how I'm going to fit to the engine and the spot that the steering pump occupies might worth looking at.
       
    12. CDW6212R

      CDW6212R Elite Explorer

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      I too wonder if it could run an Explorer rack, I want a turbo under the hood if it's possible.
       
    13. Hotrodmk8

      Hotrodmk8 New Member

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      Why don't you use the steering from a new ford truck or mustang gt500 they are both electric.
       
    14. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      integrated power steering

      I don't know specifically about the Mustang and Ford truck but most of the new electric steering systems designed to increase fuel economy use a small motor mounted below the steering wheel that is integrated into the steering column. Also, I think it is computer controlled. Incorporating that into my Explorer would involve replacing the entire steering column and possibly lower steering assembly as well as trying to kluge together an electronic interface to the PCM. I've heard that the integrated systems are nearly impossible to steer when the motor fails or electric power is lost. With the current Explorer steering if the pump fails steering is difficult but not impossible.
       
    15. Hotrodmk8

      Hotrodmk8 New Member

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      I don't think ford would make it impossible to steer if it lost power,but I have a buddy that has a new truck I will find out.
       
    16. R1dd1cK

      R1dd1cK Active Member

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    17. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      hydraulics

      Good find! From the photo I suspect the assist is via motor driven gearing instead of hydraulic pressure assist. Unless the gearing disengages when the motor fails it would be very difficult to overcome the mechanical advantage and steer the vehicle.
       
    18. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      looking for mounting space

      Today I removed the battery, battery tray and fender well to look for a possible mounting spot for the MR2 power steering pump. The photo below was taken looking down from the engine compartment.
      PSSpace1.jpg

      The next photo was taken from the wheel well.
      PSSpace2.jpg

      I didn't have time to take any measurements but stuffing the pump into that area would require relocating components and a modification to the fender well. I doubt it would be easy to accomplish and would reduce future maintainability by restricting access to components.
       
    19. CDW6212R

      CDW6212R Elite Explorer

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      How big is the pump? The area next to the battery above the body mount bolt is the only space in that area. Other than that I'm not sure if the other side under the air inlet tube is any larger.
       
    20. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      A/C line & VM valve

      If I relocate the A/C line and the vapor management valve there may be room for the pump. I was hoping that the V8 may have a different A/C line configuration but this photo by Joe Dirt of his 2000 V8 A/C line looks similar to mine.
      V8ACfitting2.jpg
       
    21. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      Fuel Vapor Management Valve

      It looks like the fuel vapor management valve (FVMV) could be relocated from the stock position:
      FVMV.jpg

      to behind the bumper below the horns and left headlight assembly:
      Horns.jpg
       
    22. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      A/C discharge manifold

      A significant problem will be relocating the A/C discharge manifold and hose.
      ACManifold.jpg

      One possibility is a custom bent and welded manifold with the refrigerant fitting located so it is accessed thru the existing round hole in the radiator support frame.
      ACManifold2.jpg
      However, that may be a possible location for a very small power steering reservoir. Another possibility is to locate a custom manifold at the rear of the A/C compressor. Either way, a longer and rerouted discharge hose will be needed.
      ACDischHose.jpg

      I will try to find a local A/C shop experienced in custom installations and discuss options.
       
    23. R1dd1cK

      R1dd1cK Active Member

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      Well since your going supercharged did you decide to give up on this idea?
       
    24. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      Still planned

      Absolutely not. Just later. The electric power steering pump possibility is part of the reason I'm upgrading my alternator (220 amp) and charge cable to 1/0 and installing new battery terminals with four wire connection capability. The alternator charge cable/starter/battery junction box/battery wiring harness is being reworked to provide more room for the electric pump and hoses. It's also part of the reason I removed the A/C manifold assembly and will have a custom one fabricated. And finally, it's part of the reason I'm locating the intercooler pump in the difficult to access location above the passenger side front body mount.
      Pump1a.jpg

      I'm hoping that by the time I actually complete the M90 installation a suitable 100 amp PWM controller will be available.
       
    25. R1dd1cK

      R1dd1cK Active Member

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      Good. I'm glad to hear this. I heard something some where that the power steering pump on the 5.0 uses about 50 hp to run.
       
    26. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      very doubtful

      I measured on the dyno the power required to drive the A/C compressor. I hard wired the compressor to run continuously and the peak horsepower dropped by 20 rwhp as I recall. I'm confident the power steering pump requires less power than the A/C compressor although I've never measured it. The max load on the engine probably occurs during parking.
       

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