Fuel Pumps

[George Des]

The discussion of fuel pumps comes up from time to time and usually the first question deals with whether it is an old style pump or new style. Believe there is still some confusion on this with some, so in order to show the differences I'll use my new found ability to post pictures to show the differences in pictures what we've tried to describe several times in words. Still plan to put togehter a detailed set of instructions on how to do the rebuilds on both, but never seem to get around to it!

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Download Attachment: oldstylepump 52.JPG
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[J. Huber]

Nice work George. You piqued my curiosity as to which pump I have. I understand that my original was the taller old-style, but I have had it replaced. So I just took a peek -- unfortunately the cover is in the way!. And, I'm not that curious...

I looked at my records and have a work order that describes the R&R. The part number is 001 091 5201 (177 bucks in 1985). There is also a note that says the mechanic "modified" the cover. Does any of this yield a clue? Thanks.

James
63 230SL

[Naj ✝︎]

Yes, James,
You have the later shorter pump.
You may be able to see the more vertical outlet if you look where the feed pipe to the engine comes out from the cover.

naj

65 230SL
68 280SL

[George Des]

James,
Naj is right--based on the numbers you give and the tiemframe you had the work done--it is a new style pump. There are actually several different Bosch numbers that cover the older,large style pump. The differences however are only apparent when you have the different numbered items side by side. The side plates that contain the inlet and outlet fittings come in a number of different varieties. One version of the pump also has a removable screw top where you can grease the top cover ball bearing. Have also detected some minor variations in the armature and brush setups and some pumps contain the radio supression .004 MF capacitor between the internal brush terminals while some don't. In spite of these differences, all versions of the older, large style pumps basically operate the same--same sealing-same bearing sizes-- and most if not all of the parts are interchangeable amongst all the old style pumps. The large style pump and the small style pump are both physically--as shown in the pictures-- and functionally different in every way except perhaps the inlet fitting.

George Des

[J. Huber]

Interesting. So when (if) the time comes to replace or rebuild it, I would be best served to stay with the newer style? Refresh my memory -- are the later ones the easier to refurbish? How about price & availability?


BTW, I have NO problem with mine not being the original style -- it gets the job done!!

James
63 230SL

[Naj ✝︎]

Hey, George,
 

quote:some pumps contain the radio supression .004 MF capacitor between the internal brush terminals

Is this it?

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Pump repaired with your and Bob (Australia)'s articles. Thanks

naj

65 230SL
68 280SL

[George Des]

Naj,

Exactly. This is the foil type capacitor. Some have a red plastic one of the same capacity. The capacitor minimizes the arching of the brushes and serves to suppress any static interference with the radio. James--the newer style pump functionally serves the same purpose as the older, large style pump and on our cars--113s- does so just as well. Many 113 ownwers opt for a rebuilt older,large style pump for originality and so they can use the protective pump shield that came on cars orginally equipped with the older pump. The newer pump uses a completely different mount and a modified protective shield because of the different placement of the inlet/outlet fittings. I've been told that output presssure and volume on the older pumps is somewhat higher than on the newer pumps and that this is a factor when providing fuel on the big 600s. Thus the recommendation to stick with these older style fuel feed pumps on the big Benz's.

George Des

[hands_aus]

Hey Naj and George,
Naj, I hope my article helped. It is a bit wordy but I wrote it for my own future reference when I become old and forgetful.
The How-to-info came from George who is a fountain of information and extremely generous with his time.
George did you ever receive the copy of that article I sent ages ago?

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