Sprintshift Hydralic pump

Hi all, new to the forum and at the outset can I say that you folks have saved me from much anguish with your concise analysis and banter regarding the dreaded hydraulic pump issues...thank you!

I bought a 316CDI 2002 (I think its a T1N?) last year with 88K on the clock. It is an Aussie ex ambo converted camper and has performed flawlessly on many a journey. Then out of the blue no gear selection and an 'F' code on the display.

Thanks to the talk here, I found that the relay was the original Bosch and had welded contacts causing the pump armature to short out. The issue has been resolved by installing the new (diode protect relay) and I removed the pump assembly and replaced the electric drive motor with an after market high torque replacement.

I was not prepared to pay the exhorbitant price MB wanted for a new pump assembly so modified the pump to accept the motor. The assembly is working well and I am now in search of other damaged pump/motor units to convert as a back up and an inexpensive option for others in the same predicament. The new motor is a bearing type motor (improvement on bushes) and draws around five amps on load.

If anyone knows where I might procure damage pump units, I would appreciate the info. If I can get a hold of some of these I can offer the replacement at a fraction of the cost of a new pump. Additionally, I am looking at a solid state relay mod for the original Bosch unit as when these fail (rare) they fail open circuit.

Hi Chooqi,

Welcome to the forum, great first post & very interesting repair of the pump Others have had the motor rewound but modifying to accept a better quality motor is a very exciting development. Would you care to share more info on this modification & possibly some photos.
In regards to a solid state relay (SSR), I looked into this years ago & came to the conclusion it wasn't worth the effort because you still need to protect the SSR with a diode due to the inductive spike from the pump motor when the SSR opens & the replacement diode protected mechanical relay is proving to be very reliable, almost bullet proof.

Cheers,
Iggy

Re: Sprintshift Hydraulic pump

Thanks for the welcome Iggy. This initial modification was performed in order to get the vehicle home, however it seems to be robust and doing the job. The original pump took about eight seconds to build pressure whereas now it achieves working pressure in about three seconds.

The motor (model aircraft starter) is slightly longer than the original so I had to space it out from the mount, however am in the process of obtaining a shorter version. The price is right at $20 and supplied by Oatley Electronics who are now based on the central coast NSW. The motor is designated SC124 http://oatleyelectronics.com//product_info.php?cPath=53&products_id=190 and seems to measure up to fit the job. I had to fabricate a support strap for the motor as the original was spot welded to the motor housing.

If I can get my hands on some discarded (burnt out) pump assemblies I will post up a photo journal of the process and procedure. In the meantime here is photo of the hydralic pump in situ.

I love mods like this. Hopefully this motor mod, coupled with the proper relay, will make the sprintshift system more reliable long term. I wonder if a brushless setup might work even better. It sux having to avoid otherwise nice vans due to sprintshift, so hopefully newer technology can come to the rescue.

What would be really nice is some kind of manual override, that can drive the solenoids/relays with simple switches if the electronics fail/won't allow. But getting the pump sorted is fundamental to any further mods

owner said:

I love mods like this. Hopefully this motor mod, coupled with the proper relay, will make the sprintshift system more reliable long term. I wonder if a brushless setup might work even better. It sux having to avoid otherwise nice vans due to sprintshift, so hopefully newer technology can come to the rescue.

Click to expand...

Hi Owner,
On the same page as you , I've already checked the great range of powerful brushless motors available, still checking the controllers to see if it can all come together & work easily with the Sprinter electronics.
A brushless motor pump would go a long way to improving the reliability of the Sprintshift.

Chooqi,
The link to the Oatley electronics motor is a 24V motor, do you think it would be suitable with enough torque & speed working on 12v

There were three main reasons I decided to try this out. Desperation..to get the van off the side of the highway. Cheapness... I just cannot pay greed, when he is already bloated. Servicability... brushes will wear and must be replaced in time and the bearings and brushes can be replaced with a few tools, on the side of the road if necessary.

I agree that a brushless motor would be ultimate, however after researching the hydraulic shifter mech in the sprintshift box the required pressure is 57 Bar. I think that it would be grasping at straws to find a brushless motor with the capacity to run the pump considering the physical size restrictions faced in mounting both to the pump body and the gearbox. However I do not discourage the possibility that such a motor exists with advanced technology and miniturization, it just comes back to cost.

I think there is a typo on the Oatley page Iggy, look down further at nominal voltage, but you are right. If indeed it is a 24v motor then it would be inadequate at 12v. They had a good range of motors back in the day, unfortunately since moving to the central coast the range has diminished considerably. Can't blame the guy, I think he is aiming at retirement and he chose a beautiful part of the country, I am sure that you would agree.

Choogi.
Once you decide to go away from the original pump you have many options, There are 12volt pumps for a wide range of uses, one is for a hydraulic lift on an outboard motor. others for steps or doors on small buses the larger buses use air pressure. Eric.

It has been a strange day of coincidences. Thank you Eric for your suggestion, it is the same conclusion I myself came to while looking for suitable motors. Why not replace the complete assembly and save a lot of effort? At one point I was thinking along the lines of mounting a pump off the air con drive, then came to my senses.

The pressure transducer that operates the pump relay seems accurate and not prone to failure. This slightly larger motor builds pressure very quickly and cuts out within a few seconds. Another thing I have noticed and can't explain is that it holds pressure for much longer than the original pump. Admittedly, I dropped the fluid and replaced it with Penrite LDAS, so I don't know if that is a contributing factor. Either way I am happy in that the pump works less than it did in duration and frequency and that is a good thing.

Hi Chooqi, I may be able to help out with a pump. Mine failed a few years back & I believe I still have the original as I was going to look at an alternative also. (We do non-mainstream automotive design and engineering) Do you want to post or PM your addy & I'll dig it out and send down.

Ciao Mozz

Hi Chooqi,

Replacing the hydraulic fluid is why your system holds pressure for longer, I have also noticed the same effect after replacing fluid. The Penrite LDAS is from my experience a better fluid than the genuine Mercedes fluid which seems to really loose viscosity with time & of course it's much cheaper.

I'm thinking it's easier to keep the pump with all the standard connections & fit a better, more reliable motor. I've ordered this brushless motor to experiment with, I just need to decide on the best brushless ESC speed controller to go with it.
http://www.ebay.com.au/itm/361813384822

I have machining facilities so should be able to fit the new motor to the pump body without too much trouble, the 8mm shaft will also be a good match for the pump drive coupling.

Will keep you informed of my progress

Cheers, Iggy

Hey thanks Mozz, that would be very helpful. I will PM you.

I am envious of you guys having machining facilities, best I have is a vice and files. Necessity is the mother of invention however and fortunately this type of adaptation is not micron dependent.

That motor look the part Iggy and not overpriced. There must be a generic controller about that is matched to the motor, I will look around and see what turns up.

Further to this mod, I have sourced a supply of suitable (brushed) 12volt motors for a very reasonable price. The dimensions are ideal and the mounting plate lends itself well to adapting the original MB hydraulic pump.

https://www.motiondynamics.com.au/united-my6812-12v-dc-100w-2750-rpm-electric-motor-chain-en.html

Although the ultimate motor is a brushless design there are a few inherent problems associated with these types of motors. In the main, they are three wire devices and require a controller, adding further cost. However the need to either encase the controller (waterproof) and mount it near the pump so as to use existing cabling or mount it under the driver seat near the relay which would require two additional cables to be installed, limits the viability. So I have decided that a brushed (ball race) motor is the simplest option and lends itself to being fully serviceable.

Putting out another call for any pumps that are defunct. I am happy to purchase (up to $40) and pay for freight.

Hi chooqi,

Have you measured the Amp draw on a factory pump motor? Just to know the replacement motor will be up to the task.

Ive been on the lookout for a spare pump myself, but havent looked too hard . I love the sprintshift.

Having a full machine shop at home makes jobs like these fairly easy.

On using a brushless motor, only thing you are gaining is the absence of brushes. The controller is the weak point, and can only be repaired easily by replacement.

bmachining said:

On using a brushless motor, only thing you are gaining is the absence of brushes. The controller is the weak point, and can only be repaired easily by replacement.

Click to expand...

Hi Ken,

Agreed the brushless controller could be the weakest link but presently the brushes ARE the weakest link in the whole Sprintshift system. The motor has bronze bushings not bearings and undersized brushes which overheat & stick requiring the classic hammer tap to get the pump working again.

I'm working on an inexpensive plug & play brushless controller so if a problem arises it's a simple job to swap the controller & get going again.

The pump motor has to start under load so the current draw would be considerable, I haven't yet measured maximum current but the fuse is 40A so I'm thinking about 20A - 30A would be typical.

Cheers, Iggy

bmachining said:

Hi chooqi,

Have you measured the Amp draw on a factory pump motor? Just to know the replacement motor will be up to the task.

Ive been on the lookout for a spare pump myself, but havent looked too hard . I love the sprintshift.

Having a full machine shop at home makes jobs like these fairly easy.

Click to expand...

Hi Ken

I also love the sprintshift with the exception of the inherent pump motor problem and am not prepared to venture off without a spare unit at the ready. I agree with Iggy that the motor current draw at startup would be 20-30amps, which indicates the load is considerable.

This mod is currently working well and I am looking at photo blogging the next one from start to finish so that it is documented with easy to follow directions so that anyone can attempt an inexpensive fix.

I also look forward to Iggys development of a brushless motor and controller, please keep us updated on any developments Iggy. I envy you guys with precision machining tools, makes the job a dream.

Cheers
Lou

I checked the maximum current draw of my Sprintshift pump (fairly new, less than 60,000Km) & surprisingly the maximum recorded was 12.1Amps. So at 13V nominal that's 160Watts motor power including inefficiency's being used.

If you doubled that figure to say a 300W motor I'm sure that would leave plenty of over rating capacity for the motor & ensure a long life.

I think I might have over specified the brushless motor I've ordered, but at least I know it'll be working easily and the brushless controller rated at 20Amps should also be over rated for the job required.

Cheers, Iggy

Iggy, Thanks for the info!

Running a speed controller with double the ratings is a safe bet.
Only other thing is motor RPM. not critical, but if its too slow it wouldnt be great.

I was going to pull my pump unit off today and have a good look at the setup, but it was 43C , much nicer in the aircon workshop. Im going to replace the fluid anyway.

Not sure how others are, but my sprintshift is super smooth and fast with gear changes. Changes up and down when you would want to change gears, very well setup.

Iggy66 said:

I checked the maximum current draw of my Sprintshift pump (fairly new, less than 60,000Km) & surprisingly the maximum recorded was 12.1Amps. So at 13V nominal that's 160Watts motor power including inefficiency's being used.

If you doubled that figure to say a 300W motor I'm sure that would leave plenty of over rating capacity for the motor & ensure a long life.

I think I might have over specified the brushless motor I've ordered, but at least I know it'll be working easily and the brushless controller rated at 20Amps should also be over rated for the job required.

Cheers, Iggy

Click to expand...

Hi
It can be extremely hard to measure the maximum current draw at startup for something like this motor. You need a quality meter to catch it, most ordinary digital meters are tooo slow. So allowing for double the figure seem wise to me. Just a comment !
Jaahn

jaahn said:

Hi
It can be extremely hard to measure the maximum current draw at startup for something like this motor. You need a quality meter to catch it, most ordinary digital meters are tooo slow. So allowing for double the figure seem wise to me. Just a comment !
Jaahn

Click to expand...

Hi Jaahn,

I used a true RMS digital clamp meter to check the current draw because I was expecting over 20A, I understand what you mean by the initial current surge to start the motor especially under load may be missed by the meter if the sampling rate is too slow. I did notice the current draw increased as the pressure was building in the pump and the data logging of my multimeter recorded the maximum just as the motor stopped.

Cheers, Iggy