Electric power steering

jeep

#1

I have a 1955 Willys CJ5 that I?m rebuilding. The problem is the steering. I have bad shoulders and even if I didn?t, this Jeep?s steering would create them. So I plan to add power steering to my rebuild. This Jeep was not designed for PS, so for normal hydraulic PS I would have to fabricate a pump bracket, mount a PS gear box, change the steering shaft, and change the steering linkage. Can be done, but a lot of messing around.



So I?m considering in a electric power steering unit form an 2007 Cobalt. Everything stays the same except the shaft and column. So here?s the problem.

The EPS has the PSCM attached. The normal power wires are there, but there are also 4 wires that are for serial data. These supply information to the PSCM about speed, Temp and also mode (there are supposedly six modes the PSCM can take depending on the model of the vehicle and its accessories) Two wires go to the BCM, two to the DLC.

My question: Is there a way to bypass the need for this input? If not, can I create a false signal to these inputs that will allow the EPS to function? I don?t know what type of data signal that the PSCM is looking for. The Willys will be used off road and at low speed, so a higher torque setting would be desirable.

I contacted GM and they referred me to the local dealer. (their default mode) When I explained that I didn?t think the dealer had the knowledge to help, I was again referred to the dealer. I posted on the GM High Tech Performance website. The editor responded that he had also thought of doing this and to let him know how it turned out.

Thanks,


#2

I think you’ll need a lot more pieces off of that Cobalt. Maybe find a wreck and strip it.

I also think you need to find a forum with engineers, not car enthusiasts.


#3

The voltage and polarity of the assist motor will be controlled by the sensor on the power steering module, but only as modified by the speed and temperature signals fed to the PSCM by the appropriate VSS and temp sensor. You’ll need to get the schamatics and the signal voltages (specs) for the power steering unit. My guess is that as speed increases the voltage to the motor will decrease up to a certain speed where it drops to zero or near zero, and it’ll probably decrease as a function of temperature also, since more power is needed for cold weather (the gears are probably in a thick lubricant).

In short, get the schematics and signal levels or bring the PSCM and temp sensor from the donor vehicle and see how it runs withuot the VSS signal.


#4

Thanks,
The PSCM is made by KOYO. Not really sure where I can find the schematics for the PSCM, since it’s not a dealer repairable part. The only voltages I’ve seen listed are from the torque sensors, which are part of the steering assembly. If I could find out the voltage range and type, I could try to reproduce it.


#5

You may not be able to get the schematic, but perhaps the requirements are printed on the label or molded into the case.

determining the voltage requirements of the steering assembly on the bench may be just a matter of ohms testing to determine the ground lead and the + and - leads and then using a variable DC voltage generator to test the assembly. Mind you, most things in life are more difficult than they seem like they’ll be, but that’s where I’d start. It’s logical to assume the motor will be DC and the polarity will be in one sirection for right turns and the other direction for left turns, probably both connecting to the same ground lead.


#6

That does make sense. The main power to the unit is a simple 60A DC connection. No question the motor is DC. Two of the four PSCM input wires are labeled +. The question is if the input is just a simple dc voltage change. It could be a modulated pulse or a digital signal. If I blow out the PSCM I’m screwed.


#7

Are you sure that you can’t drive without power steering? The vast majority of cars and trucks on the road prior to 1960 had no power steering. Even 2 1/2 ton trucks were manual steering. I taught 3 boys to drive in a 1953 Jeep and even weighing less than 100 lbs they were able to drive with no problem. Maybe it’s worth giving it a try. Once moving, turning the wheel is quite easy. It’s just a matter of anticipating the next move.


#8

I drove it prior to rebuilding it. Steering was a chore not only for myself but others also complained. Before I bought it, a smaller steering wheel was installed. The older steering wheels were a lot larger and gave more leverage. The drivers seat doesn’t move because the gas tank is under it. I can manage with the smaller wheel as far as getting in goes. I would be smashed by the larger wheel. The jeep is being used on a farm, so its speed is slow, which also makes steering harder.


#9

It sounds like getting a Cobalt unit to function properly in your CJ5 means getting into a nightmare of wiring, codes, and sensors–very much getting away from the desirability of the simplicity of a Willys Jeep. That said, it looks like there are a variety of aftermarket companies that make individual parts or even kits that can be implemented into your rebuild. I have no experience here, but doing a google search for “electric power steering” returns a bunch of options including a manufacturer that specializes in just this. You’ll get into additional cost, because presumably you can get a Cobalt pump from a junkyard cheaply, but by the time you incorporate all the peripherals and electronics you might be better off going this route.


#10

www.flamingriver.com has a unit for 6K. Not in my budget. Your right, things get complicated. I thought, if I was to do this, now was the time when I had the Willys apart. If things get too squirrelly, I’ll just punt and put it back together the way it was built.


#11

Yikes! 6k should be out of anyone’s budget for that! I had found a couple of kits that started around 900-1k (e.g., http://electricpowersteering.net), but again, I have no experience with any of them so I don’t really know what I’m looking at and if they’re really suitable for your application.

Not to steer you away (pun intended) from the electric system, but given the challenges of retrofitting an electric system, a traditional hydraulic system might not be as tough as you think. Most of the old Jeep motors were used in a variety of vehicles, so is it possible that they used it in another model that had PS, thus providing a source for the pump and bracketry? I know later Jeeps much better, so it may be different on your (early) CJ5, but a PS gearbox might even be somewhat interchangeable with your non-PS shaft and linkage. Again, I’m speculating here but you might even be able to retrofit a newer CJ5 gearbox and column.


#12

That outfit is a lot more reasonable than the flamingriver. The idea behind this was that I can get the whole electric steering assembly for about $100. If I could easily( key word: easily) get it to work in the Willys I’d go for it.
The Jeeps of this vintage were F-134’s. So F-heads with 134 ci’s. In the low 40’s in HP. There was an option for a HY-LO pump to power a snowplow. It was banded on top of the generator. With no seperate bracket. The exhaust manifold is tight to the frame rail on the drivers side and doesn’t leave much room for a power steering gear back there. The steering gear that it does have is very small. Rock climbers will run the steering shaft to the front of the radiator and have the gear in front of the linkage and just behind the front bumper. Again, more than I wanted to do.


#13

What do you mean by “rebuilding”?


#14

Body off, lots of patch welding. Engine: I was ready for a rebuild, but only needed to do the top end. So if I was going to change anything, now was the time.