Early fuel pump question...

[mrtzmd]

Hello everyone,
I began the disassembly of my early fuel pump for cleaning and possible rebuild. The pump spins freely but i found the chambers to be dirty with residue as well as the inlet filter which I cleaned. When I removed the bottom plate to inspect the impeller I noticed there was a small spring between the impeller and the endplate located in the center recess of the endplate where the shaft is located. Per the tech manual there is no spring mentioned? On a spare pump that I have, when I removed the endplate I found the small woodruff key between the impeller vanes hence it spun slowly, when I tested the pump it spun freely with the impeller removed, no spring found on this pump? Should I leave the spring upon reassembly?

[PeterPortugal]

I suggest you have a look at the technical manual fuel pump section. Somebody put a great set of instructions for disassembling an early fuel pump on there.

There should be no spring...unless you are referring to the mechanical seal (which is a bellows type).

Take note to remove the tabbed washer carefully to keep the integrity of the tab on the inside diameter....lots of posts on this recently !

[PeterPortugal]

Also be careful cleaning the residue.

Look at Kent Bergsma's "mercedes source" channel on youtube.

He has posted a video which covers cleaning of an early long style fuel pump.

[dirkbalter]

I also rebuild two recently and didn’t have springs in the described area. There should also be no woodruff key installed. The impeller and shaft are held by a regular (I believe 4mm) square key.
Check you brushes as well. Mine were worn down on both. 

[mrtzmd]

Thank you for the feedback. I realized that an incorrect diameter oring was installed on the endplate causing minor play between the impeller and endplate. I believe this is why a spring was placed to keep upward pressure on the impeller.

[mrtzmd]

  Upon removal of the impeller I realized that the pump had been "rebuilt" with an incorrect cclip and the tabbed washer is broken.. inside tab is broken off and washer essentially mangled in place. I understand that the tabbed washer is no longer available in the rebuild kits from the vendors and that these were reproduced some time ago (cannot find the thread here on the forum).  I guess I'm stuck for now with the rebuild. I understand the short fuel pump is the better option and replacement alternatives are available but I really wanted to use the original pump.
If there is any interest in having these washers reproduced please let me know as I would gladly assist in any effort to do so. Thanks

[mrfatboy]

This was just recently discussed here:

https://www.sl113.org/forums/index.php?topic=27281.0

You should be able to have them made if you can't find one.

[mrtzmd]

Thank you for the link. I posted there.
Mauricio

[Tom in seattle]

I have an early style pump out of the car due to leaking.  I read the section in the tech manual about the difficulty in disassembly.  I tested a screw and quickly determined that more torque would likely result in breaking the head off.  If I continue this project what sort of soaking material should I use to free the screws?  What is the likely result of applying heat with a propane torch? An explosion?

I can see no filter screen, do they come in the rebuild kit?

Is this effort worth trouble?  I see “new” short style pumps on eBay for $625.  Are they real Bosch pumps?  The seller says they are louder than original but work fine? 

Is there someone out there who reliably rebuilds tall pumps?

[mrfatboy]

Pay close attention to the short pumps.  There is a louder non Bosch one that will work but not desired.  Also you can get it for $100 on Amazon.  There was a thread about this 1-2 weeks ago here.

My early pump was rebuildable with the kit supplied  by authentic classics. Check their listing for parts in kit. YMMV😀

Soak bolts in PB blaster over night.

[Tom in seattle]

mrfatboy, thank you.  Had to research PB Blaster but found it.

[dirkbalter]

I soaked them in WD40 for a day or so. Still one of the bolts snapped and I had to drill it out and re-tap. Not to sure about heating the housing up to much, especially around the inlet and outlet ports as these have plastic components inside. 

[George Des]

Sometimes, no amount of soaking is going to get these screws to budge without snapping. What I do in this case is snap the heads off so that there is a stub left. The cover plates cannthen be carefully levered off by working around the perimeter of the side plate or bottom with a utility blade. This is dangerous work. Wear eye protection as you will probably snap a number of blades doing this. You may have to lever a small anount and then wedge another blade over the first. Eventually the plate will rise enough that you can get a screw driver blade inserted and be able to remove it to expose the screw stubs. Do not try to remove these stubs until you direct a propane torch flame onto them and then quench with oil or WD spray. The heating and quick cooling should shock them enough that they can be easily removed with a set of vise grips. Have done many, many this way. Just be careful!!!

[rgafitanu@gmail.com]

And if the screw stub is too short to grab it with a vise grip, you put a 1/4" nut on top of it and you weld it to the stub. Cover the impeller chamber with a wet rag. It works very well and the weld splatter doesn't stick to the pump body because it is a non ferrous alloy.

[George Des]

Yup. The last thing you want to have to do is drill out a stub. Unless you are really good, and I mean really good, it is very difficult to get a bit centered on a stub that small in diameter. The bit has a tendency to wander and if it does, it will chew into the soft aluminum alloy and make a mess of the pump housing.

[dirkbalter]

Agreed, this is not a hand drill and roughly aiming for the center kind of job. In my case, I didn’t have enough meat to grip the remaining stud. I like Radus description of welding a nut on top of the stud. That may be easier. However, I ground the remaining face of the stud flat in order to find the center. I marked the center with a center punch. Using a drill press, I clamped the housing to the (press) table. Also, instead of using a regular drill bit, I used a so called center drill to start the hole.  I work my way up, using different size drills. When I came close to the root diameter of the thread, the stud started to fall apart. With a little pick, a tap and some patience I was able to remove the remaining stud material.

[George Des]

Yeah, patience in doing a drill out is the key to this. It also takes some fiddling aroind to clamp the housing if it is a side plate stub you have to deal with. I have had to do it as you described but I hate having to resort to that for fear of ruining the housing with a slip up.