Another fuel pump problem

[georgem]

I removed the fuel pump from my  car because of a leak (its a short pump).

I have stripped it down and now have to separate the motor from the pump body as I believe the seal that stops fuel getting from the pump body to the motor has failed. My question is re the brushes - to get the motor off, I need to remove the brushes - do I just undo the screw that holds the two plastic terminal housings and just pull them out - is there a trick to this. I have undone them and the copper wire from the terminal to the brush looks to be coiled into a spring shape - does this hold them on to the commutator? or is there a separate spring?

BTW this is one of the few jobs that can be done without jacking the car. The only sad thing is a seal kit is avail from SLS for about 17euros which is pretty reasonable BUT unfortunately they want about 2.5 times this for postage - ouch!

[hkollan]

George,

The coiled cooper wire is not holding the brushes to the commutator, two separate springs do that. To get the motor out you need to remove the top cover/housing and it will be evident how to proceed.. Also to replace the two o-rings inside the plastic terminals, the wires need to be unsoldered from the terminal pins. One of the most common leaks occur there in my experience.

I have bought a few seal kits from this guy, maybe he can give you a better deal on shipping than SLS.

http://www.ebay.de/itm/Dichtsatz-fur-BOSCH-Benzinpumpe-spat-Mercedes-Benz-Oldtimer-W108-W111-und-W113-/201027931032?pt=DE_Autoteile&hash=item2ece32cb98

Hans

[George Des]

The plastic terminal pieces do not need to be removed and if the leak is not coming from there, do not disturb them. The orings under there are a square cross section and difficult to source. Most repair kits do not include them. You can remove the brushes by desoldering them but you will need to make sure that the replacement brushes have a small relief cut where the shunt is attached. Otherwise, you will have a problem placing the new brushes in the brush holder. This is described in detail in the Tech Manual. I have used the OEM Kit supplied by MB and have found it lacking. First, it contains a minimum of the seals required and second, the brushes supplied did not have this relief cut making installation very difficult. Be very careful working around that brush plate. It is riveted to the body and fiddling with the brass brush holders while trying to install the wrong type brushes runs the risk of loosening the holder attachments to the point where they will no longer hold tight to the brush plate. I took a look at the kit supplied by the source in the above post and it looks like it does not contain the brushes. There is a US supplier that has the kit that will include everything you need except the terminal orings to do this rebuild--ck on ebay. Hope this helps.

George

[George Des]

One more point on this small pump. The armature area of the pump is designed to run with fuel in it unlike the large style pump. there is no positive internal seal between the motor and the pump body. Unless fuel is leaking from the outside of the pump, you do not have a sealing issue.

[georgem]

George and Hans - great info and thanks for the replies.

If I can summarise, there are five seals for the pump:

Two about 7.5cm in dia (quite thin) for the body of the pump,
Two for the electrical terminals (sq cross section)
One about 2 cm dia for the pump body to the motor housing.
There is nothing that fits tightly around the motor shaft to try and stop fuel getting from the pump to the motor.

Correct?

BTW the thought of fuel sloshing around inside the motor with all that sparking and arcing is, to a non electrical person, a tad scary.....


cheers

[hkollan]

The kit I linked to has everything you need except for the brushes. Just had two pumps leaking through the electircal terminals, so I am a little
cautious regarding  that issue. One of the terminal leaks was actually on a  NOS pump, where probably the extemsive shelf life caused the o-rings to harden...

Hans

[WRe]

Hi,
have you looked in the technical manual here: http://www.sl113.org/wiki/Fuel/FuelPumpRebuildLater

"The following parts are replaced:
2 metallic graphite brushes
2 copper inlet/outlet fitting seals
1 motor “can” to brush section o-ring seal
1 brush section to pump housing o-ring seal
1 pump vane cover o-ring seal
1 “nose” section o-ring
3 M4x12mm Cheese Head screws w/ lock washers
6 M4x16mm Cheese Head screws w/ lock washers
2 M4 nuts w/washers"

...WRe

[georgem]

Thanks Wre, and George, your tech manual post is fantastic.

In my enthusiasm, I have loosened the plastic terminals - to see whats there -  which means I have disturbed the two seals - could I get away with putting them back on using some fuel resistant silicon gasket to help the gaskets? I don`t want to de solder the terminals if possible?

The other gaskets and copper washers I hope to be able to buy individually from a local gasket/seal supplier.

[George Des]

George,

There are a number of good sealants and gasket type compounds you can use in that area to help the orings re-seal better but do not use silicone based sealer. Gasoline will swell and jellify the silicone making it useless. Also, just abou all modern fuel pumps operate similar to the small style pump with the fuel circulating through the motor section. It not only cools the motor but also cleans and lubricates the motor internals. The early version larges style pump did have a positive internal seal between the motor section and the pump body. The sliding ring seal is the primary cause of pump leaks and subsequent failure. My hunch is that MB got tired of providing warrantef service and eventually went to the smaller pump. IMO though the large style pump is a fine example of German engineerin and will give long reliable service provided clean fuel is usedand he car is not allowed to sit idle for extended periods.

[georgem]

George,

The brush holders are loose from the Bakelite(?) baseplate that they both seemed to be attached to - looks like they were held on by two tiny ears of metal poked through the baseplate and bent over. Also the brushed don`t seem to have any indent on them - how does the indent work - I can see the "challenge of getting the motor back together - holding the brushes apart to allow the commutator to slide between them without being able to get at them. Hmmm................................

[georgem]

Just to finish this one off....

George, your explanations were beaut however I just wasn`t confident that I had the workshop gear  (and perhaps skill) to make a permanent repair - I feared that I would always have in the back of my mind that the fuel pump was a bit dodgy - so, I ordered one from Buds - reasonable price and delivered to Brisbane in 7 days.

The saga doesn`t end however. The new pump arrived with a new bracket - donut with a segment cut out with three legs attached and three mounting rubbers. When I took my old one off, it had an additional bracket attached to the top of the "donut" which in turn bolted to the chassis cross member. When I looked at that bracket - it didn`t look very Mercedes- ish.  So, can anybody help with a photo of a short pump mounted showing the brackets and how its held to the chassis.

BTW, I now have a perfectly good pump body, with no frozen screws but stuffed brushes. Easier if an Aussie wants it but happy to post anywhere for a very small consideration.

cheers

[George Des]

When a conversion is made from long to short, the small pump circular bracket is simply attached to the three-legged cross mount that was used with the long pump. I've also seen some retrofits where the short pump bracket is attached directly to the chassis. For cars originally equipped with the short pump, I'm not sure how the attachments was made, but I'm sure someone here can help.

George

[sandcrab59]

Hans
I just looked at the website for the rebuild kits and it is all in German.
How does one find out in English which kit to purchase.
Tom

[georgem]

Ahhhhh George - its now clear.

Mine has obviously been converted from long to short and as you say, they attached the circular plate of the new short pump to the three pronged bracked on the long.

I don`t have a cover, so if I can do away with the old bracket, that will tuck it up closer to the chassis and out of the way.

Thanks

[georgem]

Tom,

If you are looking at the SLS site, up in the top right hand corner of the home page they have the option to switch between German and English (click on a flag)

Many other sites have a similar arrangement.

Cheers

[sandcrab59]

I was looking for that flag.
It was not there. I have seen that on other sires.
The one you listed was Ebay not sls.
So could you show the sls site.
Thanks
Tom

[georgem]

Hi Tom,

Here is the link to the SLS site that gets me the English option


http://www.sls-hh-shop.de/#cat_66_position_36_prod_0


cheers

George

[sandcrab59]

George
Thanks for that site.
Now I have to figure out how to see the details and possibly place an order.
Thanks
Tom