Yet another early fuel pump question.

[dirtrack49]

Hi all,

I finally got back to working on my 66 230sl after being laid up for the last three months due to an accident.

Before my troubles, I had attempted to start the vehicle after it had sat for nearly 6 years. I went through the normal items such as changing all the fluids, draining the putrefied fuel that was still in the car and replacing all the hoses, plugs, cap and rotor etc. After which, when attempting to start the car,  I found that the early type fuel pump was now inoperative.

When the vehicle was sat up by my mother some 6 years ago, it was running fine. In fact, I was the one to take it out for a drive. Other than the difficulty starting it when cold, the car ran just fine.  

My question now, since I have taken the fuel pump off the car, is there anyone out there that has been successful in getting the impeller to release without disassembling the entire unit? If so, what did you do to accomplish the release of the impeller?

TIA,
Tom L.

[ja17]

These electric fuel pumps have  very little torque. They get stuck easily. Yes, just take the bottom cover off and clean and free-up the impeller.

[Jonny B]

Rubbing alcohol (correct Joe?) with some patience will do wonders on the gunk and sludge. Just use the usual precautions about something flammable.

[alchemist]

Johnny: I read many times about using rubbing alcohol on gasoline derived gunk, I even read Joe recommending using it to clean fuel level senders. Please be advised that the gung develops in tanks, pumps and so on are derived from gasoline. Gasoline and alcohol do not mix and therefore alcohol does not clean gasoline based products, because both have different nature. Alcohol is a polar compound while gasoline is a non-polar; there is no attraction between them. I know this as a chemist and I experimented by soaking my fuel level sender which was full of gunk in rubbing alcohol for few days, nothing was dissolved. In chemistry 101, there is a principle for using solvents, “like-like dissolve”. I hope this helps.

[George Des]

Be careful when freeing an impeller on an old style pump. Many times it is not the impeller that is stuck. The bellows seal also has a tendency to stick to the mating surface in the pump body. If you try to rotate the shaft, you will most likely break the driving tang on the small metal tab washer that sits atop the bellows seal. Once this tang is broken, the shaft will rotate independently of the seal and your pump will leak. If you pump is not running and it appears that you have a stuck impeller, the best thing to do is to completely remove the impeller by pulling straight off the shaft--do not twist it. Once it is off, try to rotate the shaft. If it does not rotate, the seal is the culprit and you will need to disassemble the pump as described in the Tech Manual in order to free it without damaging the tab washer. Tab washers are not available as a repair part so one will need to be sources from a donor pump or through one of the large style pump repair kits. Since the smaller, new style pump does not use the same sealing as the larger pump, this is not an issue with the new pumps and the impeller can be freed simply by cleaning it up and rotating it.  Hope this helps.

George Desiderio

[garymand]

Zalsaigh, what do you recommend?  I remember the 123 steps in solvents: water, alcohol, acetone.  Does that apply here?

[alchemist]

Gary: Acetone would not do the trick either because it is a polar compound. I would recommend non-polar solvents such as Gumout, mineral spirit, and brake cleaning fluid.

[dirtrack49]

Thanks to all of you for your input.

I am currently soaking the pancake screws in some PB Blaster. However, after reading the post from the chemist, I also seem to recall that like chemicals dissolve like chemicals. Therefore, I would guess, that one should use a petroleum product such as gasoline to dissolve any by products of the same?

If I am lucky enough to find that the impeller is the only culprit locking up the pump, can anyone tell me where I can purchase the bottom seal for these units?

Thanks again for everyone's input. I appreciate any and all help that comes my way.

Tom L.

[ja17]

I don't know the chemistry. I do know that I tried a wide variety of solvents, (carb cleaner, lacquer thinner, paint reducer, acetone, mineral spirits, brake clean, gasoline, injection cleaner.) Rubbing alcohol worked by far the best for me! Use what ever works, I'll keep using alcohol until I find something better. I just cleaned up a old fuel varnished fuel pump with it last night and it worked great. I guess my fuel varnish didn't go to  chemistry class either?  

[dirtrack49]

George and Joe, thanks for the further updates.

I will attempt to get the bottom of the fuel pump off tonight. I have been soaking the screws in PB Blaster and have tapped at them with a screwdriver and hammer.

If it ends up being the impeller, I will try some rubbing alcohol first.

Is there a part supplier for this unit?

Thanks again,
Tom L. 

[George Des]

Tom.

Ck through some of the posts. I think the bottom seal is a 70mm x 2mm or 70x 1.8 nitrile oring but ck through the posts to be sure. McMaster Carr has these.

[dirtrack49]

I guess I must of got lucky. All of the pancake screws came out of the bottom of the pump without any issues. I had soaked the screws for about five days and tapped on them daily. After removing the screws, I used a plastic handle of the screw driver to tap off the bottom cover.

The pump has been sitting idle so long that the impeller has made an impression of itself on the bottom pump cover. I can see that if this impeller runs with very close tolerances, the little bit of gunk buildup would most likely keep it from running freely.

One item that I find rather odd, there is a lot of play between the impeller and the shaft that it rides on. I am talking about 15 degrees or more movement of the impeller before the shaft begins to turn. Is this normal?

TIA,
Tom L.

[George Des]

Tom

That amount of play is normal.

[dirtrack49]

Cleaned out the pump with "Alcohol" and now it works just fine.

Went to NAPA auto parts and dug through their assortment of o rings and got a bottom o ring for 34 cents. Sure beats the ridiculous price from Mercedes and some of the other suppliers. Not only it was a nitrile o ring, the parts guy gave it to me for free since it would have cost him more to run up an invoice on it. What the hell is wrong with some of these totally out of control prices from some of our Mercedes parts suppliers???

So after testing the fuel pump, I decided to give it a go at starting the vehicle even though I figured the injection pump would be in need of attention. Much to my surprise, after several attempts, the car runs great!

After a test drive of a little over 7 miles, I put the car in park, brought up the hand brake and proceeded to open the garage. When pulling into the garage, all of a sudden, no more gears. The vehicle now moves forward no matter what gear I place it in. When the engine is off, I can push the car in any automatic transmission gear position.

Although I had not got to the transmission service yet with this awakening of this car, I have no idea what has taken place to cause the vehicle to stop changing gears.

Any thoughts? I may post this as a separate thread after I make a search on transmission difficulties.

TIA
Tom L.

[230slhouston]

The gear linkage bushing may be worn out. Crawl underneath and check the nylon bushing attaching the linkage. I had this issue.

MB

[Jonny B]

I would concur, the bushings can leave you stranded. You may also want to check the mount at the rear of the transmission. If you are going to be doing some other transmission work this would be a good candidate for pre-emptive replacement.

[rb6667]

A very common issue  

Take a look at     www.sl113.org/forums/index.php?topic=16728.0

[KevinC]

A very common issue  

Take a look at     www.sl113.org/forums/index.php?topic=16728.0

Yep...happened to me, too! The only time my car was thinking of leaving me stranded. However, my bushing fell off in my brother's driveway. He is a transmission shop owner (!) and knew exactly what to look for. I popped the old one back on to at least get me home. The local MB dealer had the bushings IN STOCK so I was able to correct the problem the next morning.