Converting SLS mechanical pump to electric
 

I know it's been done. Does anyone have any information on the procedure?

- Can anyone recommend a suitable pump for the job?
- What sort of volume does the new electric pump have to move?
- How much pressure should the pump be able to handle?
- Where is the best place to wire it into the electrical system of the car?

I'm looking at dropping a 300D motor into my 300TD, the way I seem to go through them it would be a hell of a lot easier to be able to drop the ever so plentiful 300D motors in when I need to rather than hunting forever for 300TD motors. Plus I can almost always get the 300D motor for about 1/3 that of a 300TD!

It's been discussed on here in the past, but to my knowledge no one on the forum has done it. I remember someone claiming that it would not be possible to get the kind of horsepower electric motor necessary to produce the high pressures of the system operating on 12 volts. (or something similar to that)
I've always wondered why MB didn't use the power steering pump to power the system.

On my 87 300TD they use whats called the 'tandem pump'... that piggy backs on the power steering pump. 2 for 1 kinda thing. They are still separate oil circuits though.

There is a thread somewhere where somebody had an electric pump mounted on the passenger side fenderwell up under the hood. I'll do a little searching while I have some time.....

Can that pump be retrofitted to a 123TD?? Seems better than an electric one.

that would be awesome if there were a way to retrofit a 124 sls/ps pump onto a 300d motor, but some how I think it sounds too good to be true.:(

I found this photo of an electrical conversion, but can't seem to get any info out of the car owner about the pump, voltage/pressure/volume/manufacture/etc... it's not that he's not willing to communicate, just that he bought the car with the pump installed and doesn't know anything about it really.
However it is a very inspiring photo!

THAT is the pic/setup that I was talking about......

I know this is an old post but anyone every find that pump?

Or convert a 124 ps/sls pump to a 123?

so i have the same type pump now and it KINDA works not too sure how well bu it does....can anyone else help out?

Help out how?? You haven't given us any information really......;)

I would think most any 12v hydraulic power unit would work, provided it's small enough to mount where you need it to. Trouble is that they're usually pretty expensive. Try looking at ebay for man-lift power units, snow plow pumps or lift gate pumps. You may also check out power tilt/trim units from boats.

They would also need to be rated for the always-working SLS. Many 12V pumps only have a duty cycle of a few minutes to an hour.

I didn't realize it runs all the time. I would think a SLS would only adjust to maintain an "average" ride height so that it's not constantly adjusting every time you go over a bump.

Its always pumping fluid. Crawl under one and play with the level arm, it will respond to any up and down movement.

Princess auto carries a lot of hydraulic equipment and accessories and TSC stores as well.your looking for a continuous duty 12v unit with appropriate output pressure.not sure what your car will need but perhaps someone else will chime in:)

The one i have was from a toyota convertable.

It pumps for a while then turns off then starts again almost like its saving its self.

A couple years ago I had a Euro TD that I was going to make into a 240TD so I had to come up with another SLS pump. I used a "convertible top" pump. I had new hosed made up and the pump mounted then abandoned the project. The guy that bought the TD got it going and said it worked fine, only thing is, he had to use a different filter. I found a "generic' convertible top pump on eBay.

Those are power hungry little pumps, no way I'd let one run all the time. A one way hydraulic solenoid valve could be added to the hydraulic fluid circuit (on the return line), it would then become a manually controlled system, power up and gravity down, at the drivers discretion... I'm wrestling w/ this now... heres my pump, its mounted in the spare tire well.

http://rbk3.com/mbz/83td/hyd1.jpg

http://rbk3.com/mbz/83td/hyd5.jpg

so i read somewhere you have to get rid of the MB oil tank and filter ...anyone know this ?

This is how someone else did it.

So i guess you have to kill the oil canister and filter.

http://www.benzworld.org/forums/w123-e-ce-d-cd-td-te-class/1344008-electric-sls-success.html?highlight=Electric+SLS

no one?

why not get a small belt driven pump- like maybe even a power steering gear pump, and use that?

I imagine it would work fine. if you didnt care about the AC, you could mount it there.
or up by the cc actuator? how many peeps have functioning ac/cc??


I also would imagine that you could replace the leveling valve w/ an electric switch to run only when needed, or add a switch to an arm on the rear torsion bar.

What about the hydraulic pumps that are found in "low riders"? Those use some very high powered pumps but I think they also use more than one battery.

boat autopilot pump sounds like a good bet to me, 12volt,reversible built to be used in almost continius duty constantly switching directions and available in different pumping volumes.What else would you need? My $.02 Don

I bought the hydraulic system from a VW Cabriolet, looks like it or something similar would be a suitable pump provided it is not running continuously.

I'm guessing with some thought an Accumulator Sphere from a Citroen Xantia or BX could be used as a pressure store.:)
--Dont think you could use a sphere from the M.B. as this has the bump/rebound valves inside as far as I know.

The Citroen Accumulator Sphere is made for this very job as a pressure reservoir, running at about 50-100 bar, as I recall and has no valves in the sphere itself....

A sensor switch would then cycle the pump as needed to give a pressure within the normal range for the SLS system....

. . .if those spheres were ever to make their way across the North Atlantic.;)

True true - but you guys are the home of this:-

http://en.wikipedia.org/wiki/Lowrider

There must be something similar where you are - and I guess these days you don't even have to drive downtown!

Why not just use an extra TD sphere?

Isnt the 'Bump and Rebound' valves (That form the 'shock-absorber' in connection with the actuator on the trailing-arm) in the entrance to the M.B. SLS Sphere?

The Citroen one--The actual Accumulator-- is made for just that job. They are pretty cheap and wouldnt be much to send overseas....:)

Here you go--

https://secure.gsfcarparts.com/shop/results.asp

Bugger, Cant link to the page, Anyway they are 23 quid each, do a search on that site for Citroen Xantia Sphere, it'll bring up all the various ones used on that model--There's loads, but its the accumulator that would be needed.

I defo know the bump-rebound valves are in the spheres on Citroens....

With MB accumulator spheres, the opening to the sphere is without any valving that I'm aware of, in fact a suitably diametered screw driver or similar object can be inserted until it makes contact with the fitting on the rubber bladder. With that done sufficient pressure can be applied to push against the bladder and roughly access the state of the nitrogen charge contained by the bladder or in the alternative determinr that the bladder has failed and it contains no nitrogen charge.

I'd suspect any hydraulic damping valves would be part of the struts themselves, the accumulators act as pneumatic springs not dampers. The FSM should show a cut-away view of the accumulator construction somewhere, that would definatively answer the question. And somewhere there is a thread where someone dissected an MB accumulator showing its internal construction also.

Billybob-

You're prob right. I just suspected that those valves maybe in there as thats where the Citroen's valves live, and Ive not had my 'balls' off.:eek:

Only real difference between the Citroen system and the M.B. SLS is that the Citroen has no road-spring at all. The entire suspension is on the actuator, (Strut) Sphere and Hydraulic pump.

--On the Citroen, The Brake-System is also supplied with pressure from the suspension system hydraulics, one reason why its important the accumulator is good on a Citroen!
--Lose the hyd. pump with buggered Accumulator and you have only the hyd. pressure in the suspension left to operate the brakes!!:eek:

If there's no valves in an M.B Suspension Sphere, then it would be an ideal candidate as an Accumulator, as its pressure-range is 'correct' for the SLS system pressure....

The way we used to test Citroen Spheres should also work on the M.B. ones too....

Hitch them up to an Injector Pop Tester.

Pump it up, and a good Sphere will rise in pressure until a point where pumping doesnt seem to increase the pressure any more, or if you look carefully, the pressure rise is much slower per stroke (Around 50-70 bar for the Citroen)--This is the actual pressure Inside the Nitrogen side of the Sphere....
--Whats happening is the Nitrogen and the diaphragm are compressing slightly with the pumping and as such you can read the actual pressure of the Nitrogen side, without messing round.....:)