Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: BaronYoungman on July 04, 2020, 19:16:51
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Here's an illustration of the impeller situation.... Outside of the old gas eating away at the vanes see picture1 then there is the part just wearing out see picture #2 and #3 for someone definitely got their use of this impeller but you can see the steel shaft hitting into the aluminum impeller even with the extra hardness of the Chrome Center eventually just causes the impeller to totally round out making it useless as the shaft spins around it, or in this case pushes it into the housing and jams it , causing it to burn out. This is the reason I went to fabricating stainless steel impellers. Just my two cents Bob
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Hi Bob
since the impeller broke in my almost new pump, the subject of impellers and Bosch fuel pumps became close to me. I lost a lot of time to find a new pump for a reasonable price. I noticed that also the same situation you have in US regarding the prices.
Since this time I know how important issue is the impeller- in fact it is the heart of the fuel pump.
But as user may I ask you a question? I understand that stainless steel is much harder than I do not know if this is a pure aluminium or what material?
But is your impeller not to heavy? Did you made some stress tests?
I am asking as a potential customer.
Sebastian
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I've seen pumps with brass impellers. Anyone else seen that? It was in very good condition too.
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Did you have seen the brass impellers in the Bosch short fuel pump? Because to tall Bosch pump had the impeller made from brass- and as far I know this kind of pumps are more resistant, but not any more produced. The tall pump was build untill 1968 and than replaced by the short pump.
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Are your impellers available yet?
This is the reason I went to fabricating stainless steel impellers.
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To answer the questions yes it is slightly heavier.
But because the majority of the force is used up in pushing the gasoline the weight difference of 12 grams(58g stock vs 70g stainless) is negligible. With my testing gear I found no difference after 15 minutes of running in the volume.
As for selling the stainless steel impellers I sold out my 1st two runs ( I posted here and was sold out in 2 days)and just have a few I use for my pumps.
If I do another run I will be sure to announce here first. Bob
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Darn how did I miss that? Im here almost every day, and had expressed interest a year or so ago when you were kicking around the idea. Well if you make a "list" please include me, so I dont miss out again.
As for selling the stainless steel impellers I sold out my 1st two runs ( I posted here and was sold out in 2 days)and just have a few I use for my pumps.
If I do another run I will be sure to announce here first. Bob
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I am in the same boat, on here every day and also interested but must have missed the post by Bob.
Garry
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I see you gave up on the titanium version? Wasn't one of the originals some kind of hardened aluminum alloy?
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Michael I still have one of two prototype titanium set aside for you gratis for all your help. We just haven't run into each other for me to give it to you. I just found that the titanium version was almost twice the price of stainless steel and even with the titanium being lighter than the original aluminum there was no discernible difference in the flow and PSI. So it makes no sense to do impellers out of titanium when the same results could be achieved and solving all of the deterioration issues of the original with just using stainless steel. Bob
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Did you have seen the brass impellers in the Bosch short fuel pump? Because to tall Bosch pump had the impeller made from brass- and as far I know this kind of pumps are more resistant, but not any more produced. The tall pump was build untill 1968 and than replaced by the short pump.
I think it was a short pump but maybe someone changed the impeller.
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Dan I have never seen one in brass. And the two impellers ( long pump and short pump) are not interchangeable. But brass is stronger than most aluminum (depending on grade) so that would make for a good idea. Most brass contains some aluminum. Bob
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Hi Bob,
But what about the interaction of the stainless steel impeller with the aluminium housing. Did you made some tests for the durability of this combination? And if the stainless steel do not wipes the housing?
Thank you!
Sebastian
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...what about the interaction of the stainless steel impeller with the aluminium housing...
I cannot answer for Bob as to what he's done testing wise, but understand this project began in October 2017 so he's been at it for a long time.
There is a known interaction between stainless steel and aluminum, when in the presence of an electrolyte. An electrolyte is a compound containing
Sodium
Potassium
Chloride
Calcium
Magnesium
Phosphate
Bicarbonate
I'm not a chemist, but I don't believe that petroleum has this characteristic. Gasoline or petrol is a complex hydrocarbon. In our fuel pump, the impeller is bathed in petrol/gasoline.
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Hi Michael
I am asking about this all details because Bob is doing a great job. I am interested to have at least one such impeller on stock (just for any case) for my cars.
Sebastian
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+ 1 ....! :D
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I have two long pumps in pieces right now and both have brass impellors.
One of the failure signs is fuel coming from the small orifices in the side of the pump but I haven't yet worked out what it is internally that must fail in order for that to happen. Do you know Bob?
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Colin,
If you are talking about the little pipe stub that sticks out from the side of the pump body then that is what handles leakage from the mechanical seal. The seal keeps fuel out of the motor area. Any leakage past the seal (ideally there should be none) will be routed to the pipe.
Hope this helps.
Peter
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I have two long pumps in pieces right now and both have brass impellors.
One of the failure signs is fuel coming from the small orifices in the side of the pump but I haven't yet worked out what it is internally that must fail in order for that to happen. Do you know Bob?
When my long pump failed, indicated by fuel leaking out of the side pump the problem was a broken 20 cent o-ring on the shaft. Replaced o-ring and pump still is going strong 4 years later. I also had to replace it 20 years ago.
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MrFatboy,
You are right with that as the mechanical seal is a push fit over that o-ring.
Regards
Peter
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Colin,
If you are talking about the little pipe stub that sticks out from the side of the pump body then that is what handles leakage from the mechanical seal. The seal keeps fuel out of the motor area. Any leakage past the seal (ideally there should be none) will be routed to the pipe.
Hope this helps.
Peter
Not that stub Peter, the two small holes just below the joint between the motor body and the pump body.
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my long pump is brass, this one is original.
I had leakage out the vent holes and fixed it with the small O-ring on shaft.
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Colin,
I thought the pipe stub was an obvious question from a man with your experience but I have never noticed the two small holes close to it before.
They seem to be lined up with the two inserts inside the pump body.
Photo attached to show the inserts. The holes are on the adjacent exterior part of the pump body.
Hope this helps you find an answer from other posters Colin.
Cheers
Peter
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Colin,
Out of interest do you know anyone who can helicoil a pump body as I have made a mess of one trying to drill out sheared bolts?
Cheers
Peter
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I would do it here and use timecerts, not helicoil.
As for the leaks, yes it's coming via those two inserts. I've only had a cursory glance at it (this used to be a delegated task.....) but there only appears to be the O ring on the shaft to prevent the passage of fuel. I'm sure that can't be the case and I just need to get my specs on and have another look.
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OK, I've answered my own question.
There's a brass bellows that slides over the shaft which is locked to the shaft by a locking plate and circlip.
The "O" ring on the shaft seals inside that bellows to prevent the passage of fuel up the shaft, into the motor body and out through the two small vent holes.
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Colin,
Those two inserts, and the holes in the side of the casing, are above the hole which allows leakage out to the little pipe stub. To go back to your original question it is still not easy to understand why fuel would come out of the holes in preference to the pipe.
I will be real interested in the answer if anybody does come back with one.
Regards
Peter
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OK, I've answered my own question.
There's a brass bellows that slides over the shaft which is locked to the shaft by a locking plate and circlip.
The "O" ring on the shaft seals inside that bellows to prevent the passage of fuel up the shaft, into the motor body and out through the two small vent holes.
Correct. There is a write-up in the tech section with pictures
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I wish I could help regarding the long pumps. I have tried working on them in the past but I have been frustrated with the system, so I've just concentrated my efforts on the short pump, which due to its design and materials I can guarantee performance and tight seals. By applying more modern materials and Technology in both Viton gaskets and improved techniques / glues for Armature rewinding I have actually improved on the original designs. Although again I'm improving on a design that has lasted in some pumps 40 years plus which I'm always amazed by when I get them to rebuild. Some have never been taken apart since they left the factory. This just demonstrates a good and robust original design of the pump. Bob