Leaky fuel pump, help needed

[karmannghia60]

Hi
Need help with a leaky fuel pump on my '69 280sl. The outlet hose burst so I bought a new one. Had to remove the pump from the vehicle. After refitting the whole thing with the new hose, I noticed that the pump is leaking all over. On closer inspection, its leaking from where the top cover (where the pump motor is) and the pump housing. I pulled it off again and dismantled it. I found that the motor housing was full of petrol. That can't be good, can it? I would've thought this is a dry area. Having petrol around the motor has to be extremely bad. I don't know how the petrol is getting into the pump motor housing but I can see there is a verticl hole (from where the fuel inlet is) which lines up another hole at the bottom of the pump motor housing. Should this be blocked? Why on earth would Merc Benz do this? I must be missing something. Here are couple of pics showing the pump halves and the two holes as well as the pump in car and where the leak is. Help please, the car is off the road.
http://au.pg.photos.yahoo.com/ph/rafikdous/detail?.dir=f740&.dnm=d502.jpg&.src=ph
http://au.pg.photos.yahoo.com/ph/rafikdous/detail?.dir=f740&.dnm=4e8c.jpg&.src=ph
Thanks
Raf

[jeffc280sl]

The fuel pump is supposed to be immersed in petrol.  I remember being very surprised by this.  Do a search on "fuel pumps" and you should find a wealth of information.  Why not try a rebuild kit.

Jeff C.
1970 280SL 4-speed

[Naj ✝︎]

Hi, Raf,
You have a later type of fuel pump and the motor does indeed run in fuel! Keeps it cool.
You can buy a repair kit for the pump which includes 'O ring' seals for motor housing to base and another for base to bottom cover, and a pair of brushes. The motor housing should go back on the base in the same spot - if its turned round 180 degrees, it will run in reverse and not pump any fuel.
If you do a search on fuel pump, there are quite a few discussions about the pumps.

naj

p.s: Sorry Jeff, seems we posted simultaneously  :x

65 230SL
68 280SL

[karmannghia60]

Thanks for a quick and helpful response. Put my mind at easy

[hands_aus]

Hey Raf,
Go to a "bearing and seal" shop and buy the O-rings for about $2.50 total. Make sure you tell them it is for petrol and not water.
Check the brushes for length, they may not need replacing.
The bearings will be cheap to replace (if necessary) probably about $11.00 for both.
It is a job you can do yourself or take to a small engineering shop and have them do.

Much better than buying a new pump from MB for $900.00 + gst

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[George Des]

Raf/Bob,

No bearings in this pump needing to be replaced-- the large style pump is the one that has the ball bearings. This should be a fairly easy fix, but you'll have to take the pump apart to do it and that's where you can run into problems--the screws often times "weld" themselves to the pump body because they are steel and the pump is aluminum. Once you get it apart you should replace all the o-rings that have been disturbed--not just the offending one. Also a good time to clean out all that gunked up gasoline and do a good evaluation of the brushes as Bob said. Good luck


George Des

[mbzse]

quote:Originally posted by Bob; hands_aus

Go to a "bearing and seal" shop and buy the O-rings

For the 280SL electric fuel pump (small model) a rebuild kit is available. Kit has new brushes and three of the six needed O-rings. Small O-ring mounted inside of pump (8,5x13x2) is missing as well as the seal rings at the electrical connections (red and brown plastic parts). BTW, these O-rings should be a square cross section. To disconnect the electrical connections, these must be soldered off.
The large 71x2mm O-ring seal between upper and lower pump body halves is not in the kit either.
Repair kit No is A 000 586 0147. The large, 70mm dia O-ring for the flat lid at the bottom has part No A 010 997 5045 and is furnished with the kit. The separate order No for the pair of brushes is  A 000 548 0442.


/Hans in Stockholm

[bcjm]

Sorry to hijack this thread.  I have a leaky fuel pump (newer style) and have couple of questions after reading the messages.  
1. My fuel is leaking out of the + terminal.  Does the rebuild kit come with the terminal seal o-ring?  If not is the o-ring still available?
2. How is it possible that the motor is immersed in fuel?   Why doesn't short the circuit?

[erickmarciano]

I am also rebuilding my fuel pump , but did no not remember how I removd the motor bell . can I start it dry to see if there is any sucion from the inlet pipe?for  The large 71x2mm O-ring seal between upper and lower pump body halves I ordered an extra A 010 997 5045
any one know the part # for the little oring in the pump that is not included in the kit?
thanks and happy new year

thanks


1971 280sl
1962 VW
1954 Allstate vespa
1958 gs150 vespa
1962 gs160 vespa

[George Des]

Erik--there is an easier and less potentially damaging way to check that it is mountd correctly. Remove the bottom portion of the pump, connect the terminals observing the correct polarity and ensure the shaft rotates consistent with the arrow on the bottom of the pump cover. Your method of running the pump dry to check suction w/o liquid running through it will not work, because the way these pumps operate, the liquid provides the sealing action that creates the suction action. Though it is not as damaging to run dry as on the older style pumps with a mechanical shaft seal(There is no such seal on the newer pump), running the newer pumps dry is still not recommended because it can cause scoring on the vane contact surfaces on both the pump body and pump base cover.

George Des

[erickmarciano]

thanks Georges  before reading your post I say the arow on the bottom plate
thanks
Erick

1971 280sl
1962 VW
1954 Allstate vespa
1958 gs150 vespa
1962 gs160 vespa

[erickmarciano]

can I test the rebult fuel pump with a 5 gallon of parts washer I have?

1971 280sl
1962 VW
1954 Allstate vespa
1958 gs150 vespa
1962 gs160 vespa

[George Des]

Erick,

It depends on what kind of parts washer it is. I do know that some of the stuff out there that is sold as parts /carburetor cleaner in a 1 gallon can will play hell with the nitrile o-rings. To be safe, I would get some kerosene or diesel to check it out. This is what I do and I do it primarily because I don't like having an open source of gasoline vapors around any potential source of sparking that could cause an ignition of the vapors.

George Des

[erickmarciano]

no no the 1 gal stuff is way to strong it will melt anything , I am talking about the stuff for the red parts cleaner machines

1971 280sl
1962 VW
1954 Allstate vespa
1958 gs150 vespa
1962 gs160 vespa

[erickmarciano]

If I want to test the pump off the car should the pump be fed with gravity or will it suck up the liquid ?
thanks

1971 280sl
1962 VW
1954 Allstate vespa
1958 gs150 vespa
1962 gs160 vespa

[Naj ✝︎]

Erick,
There's hardly any vacuum with air but if you prime the pump up with fluid (or suck the air out by mouth  :twisted: ) it will work.

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naj