Leaking fuel pump 350SL

Hello,

my fuel pump leaks just under the plastic ring on which the electricals are mounted. The leak is not strong and was even not visible when the pump was dirty. Is there a way how to fix it or do I need a new pump? I would appreciate any advise on this.
Thanks&Regards,

Dodi
1972 350SL

Hello Dodi,
Volker says they can be repaired.
I installed a new one
Hans-Jürgen

Hello Hans-Jurgen,

Where did you get it from? I contacted the SL shop but I am not convinced about the one they offered to me, it looks different than mine. I will ask them for parametres if it's not high a pressure k-jet.
But I would prefer to refurbish it if posssible. Maybe the seals could be replaced by other(which?) ones.

Hello Dodi,
please enter Benzinpumpe reparieren in the search field
In my car 1973 was a Bosch pump
Hans-Jürgen

Hello Dodi

When the pump is leaking on the electrical plug then it is the smaller O-Ring there that is dry and old and that is the reason for the leaking. In fact the pumps can be opened. It is quite complex as one has to have some tools and patience. The tool I used to open the pump is an kind of "expanding bearing puller" that I fixed with metal straps to the screws of the upper section an then gave puller shocks with the reverse hammering. But first one has to unbend the locking marks on the case. 
The wiring inside the Pump has to be cut to be able to change the ring on the plastic part that holds the electrical wires. You will have to solder them together afterwards when you will reassemble the pump - so mark them to solder the right ones together otherwise you pumps might turn the wrong way around .....
Having changed all the seals with petrol resistent o-rings. 
Don't forget to check the carbon brushes also and change them if they are worn out.
I have a box with different sizes of seals and this was helpful. The larger seal of the casing itself was given to me by the local hydraulic-repair shop. Unfortunately I have not written down the sizes of the seals as it was just for a trial and I did not really believe to get the operation done. Just wanted to play a bit...but it is a succes. The pump works fine now again and isn't leaking anymore.
All the best from France, Roland

Hello Roland,

thanks a lot for these information, I think it´s worth trying. Just one thing, if you say "unbend the locking marks on the case", can you provide me with more details to this? Thanks.
Dodi

The metal has been a little pressed in. This has to be undone with a flat screwdriver to be able to disassemble the pump in two.
Afterward you will have to give them again a gentle punch to secure the reassembly like on the photo. 

Thanks, it's clear. How did you reassemble that two parts after so that they keep firmly holding? Did you put there some sealant?

Hi Dodi

As written before in my description you'll need three o-rings to seal. One small one for the electrical part (that in your case is leaking) and then one bigger one for reassembling the casing (pressing again the two parts together with the larger O-ring placed and then gently putting down those locking marks to hold everything together. The third O-ring is for the pressure producing part.
You'll discover it just by doing. The only tricky thing is as said: undoing the casing using the reverse hammer fixed on the pumping unit screws (4 of it ) with metal bands with hole of the screw sitze. Place two of the band crosswise and place the puller. Then you just need  a good soldering iron to get the electrical wires inside the pump soldered together again with tin. As described earlier.  
And now: go for it. It's not so difficult. Just make sure you'll don't loose some tiny parts - I tend to use an old ofen - tray. 

Hi,

just a word of warning: Opening those noses by brute force will creat whole housing to loose roundness. Then even a renewed O-ring will not be able to seal again. You need force to open but you also need to ensure that the rest of the housing stays in shape.

Hello Roland and Volker. Thanks a lot for your help. I appreciate it.

Best Regards,
Dodi