124 fuel tank sender and strainer - PeachParts Mercedes-Benz Forum

dieselmania · #1 11-15-2012, 08:16 PM

Is there a write up somewhere on this? Any special tools I will need?

El ZORO · #2 11-15-2012, 10:45 PM

Quote:

Originally Posted by dieselmania

Is there a write up somewhere on this? Any special tools I will need?

Both the strainer and the sender use a 46 mm or 1 13/16" tool. The sender you can usually get a wrench onto the nut and turn it, the strainer you usually need a socket as there is no way to swing a wrench because of where it's located.

When pulling the strainer you should have a new replacement gasket handy or available. True Value hardware stores carry large O-rings that will work. The old one will be hard and might break as you remove it. It's hard enough to torque it back into place without having to reseat an old O-ring.

After running down the tank as much as possible drain as much as you can (the best way to accomplish that is to use a cheapo drill powered pump to suck the fuel from the fuel feed line in the engine compartment into a fuel can or use an extended section of hose attached to the fuel return at the secondary filter head and redirect the returning fuel into a fuel can, just pay attention that you stop the engine as soon as you see air entering the primary filter, you don't want to run the IP and fuel loop at the engine dry, that will just make starting the engine a problem once you get everything back together after dealing with the strainer issue). Then at the tank, under the car, above the axle, on the passenger side clamp the flex line with vice grips or something similar to prevent diesel from constantly dribbling out, remove the hose clamp that secures the flex hose to the steel line, separate the lines (be ready to have any remaining fuel in the steel line run out, have rags ready). Then you can peel back and disconnect the rubber boot that covers the opening in the underbody sheet metal that allows access to the strainer itself, loosen the boot and slide the boot down the flex line a couple inches, hold your thumb over the hose end, unclamp the vice grips that are below the now loose boot, and reclamp them above the lowered boot, catch the diesel that comes out of the hose when you remove your thumb with a rag. Then you need a 19 mm crowsfoot to remove the flex line's fitting from the strainer. Sometimes the entire strainer will uncrew as you try to remove the flex line fitting, if it does great. Have a couple containers ready to catch the diesel that will come out, make sure they are close at hand and that they will fit under the car! Could be a quart of diesel could be a couple gallons! Be ready for either.

With the flex line removed you can get the 46 mm socket onto the strainer, you'll need a couple reducers (a socket that large is usually 3/4" drive at least) and a couple extentions to reach up to the strainer, and a large ratchet or a breaker bar. It can be a challenge to hold the socket on the strainer and apply torque to the breaker bar, you want the breaker bar below the axle so you can get the swing you need and a good pull. Break the strainer free and then you can unscrew it by hand usually, be prepared for more diesel to drain down when you finally remove the strainer. Have a couple rags ready so that once the diesel stops draining you can stick a rag or two up into the space that is between the fuel tank and the steel underbody, it's maybe 1/2", because a little bit of diesel will drip out of the opening and sometimes rather than falling straight down it will run off to the side a bit. If that happens it will get into the space between the tank and the chassis and your trunk will smell like diesel for a long time afterwards.

Clean the strainer with gasoline or carb cleaner, if there is obvious scum in the tank, you can get a couple gallons of fuel and pour it into the tank from the filler and hopefully flush much of it out that way, use a couple buckets and a funnel underneath. Then once you pour the fuel through, let it settle, then pour the clear clean fuel on the top back through again until you don't have scum particles coming out any more.

Assemble the strainer with a new O-ring, lightly oil the O-ring so it doesn't stick and deform out of position as you retorque it into place. If your flex line is intact you can reuse it, or you can replace it, or you can cut the old hose off the fitting and attach a new section of hose to the bibb on the fitting and secure it at that end with a hose clamp. Put the rubber boot over the line and manuver it into position with its edges secured over the opening's surrounding lip, make sure it's in place and not twisted, its purpose is to seal the chassis opening from water and grime getting into the trunk/tank area. Reattach the flex line to the steel line with a hose clamp and the job is done. You can then grab your bottle of Dawn and hit the shower to stop the diesel fuel burning in your armpits!

The sender can be carefully disassembled and then you can soak the bottom section in gasoline to disolve any sediment/slime that has accumulated inside it over the years. Be careful of the wires, better to not touch them just use soaking or maybe a spray can of carb cleaner. If you have a hesitant reading fuel gage or a funky reserve light function cleaning the sender will usually correct those things.

dieselmania · #3 11-15-2012, 11:19 PM

Wow thanks for the detailed reply! Now all I got to do is burn 3/4 of a tank. Will get parts together and post back once I am finished.

charmalu · #4 11-15-2012, 11:26 PM

DIY w/pix -- W124 fuel sender disassembly/cleaning/testing

Charlie

dieselmania · #5 11-16-2012, 08:29 AM

Many thanks to both of you

dieselmania · #6 12-26-2012, 08:12 PM

Well driving to work and back it took my wife over 5 weeks to run the tank to empty. I changed the strainer out today, it was black but no scum or particles in it. I reached around up in the tank with my finger and could feel no scum, but my glove did come out very slightly black. I did have an algae problem about 10 years ago which I cleared up with Diesel Doctor, and other than changing the filters a couple of times had no problems after that.

Next I removed the electrical connector from the sender. I had noticed some stains on the outside oif the tank where fuel had run down from the sender area. When I removed the connector, it was dripping wet. I have not gone any furthur, wanted to check here first to see if this means I will need another sender. Don't want to waste time trying to fix the old one if I am going to need a new one anyway.

charmalu · #7 12-26-2012, 10:45 PM

If the connector is wet and there has been fuel leakage down the side of the tank, either the seal is bad or the sending unit is loose and needs to be tightened.

There could be a crack in the plastic connection piece on the sending unit as I posted in the link in the above post..

Charlie

dieselmania · #8 12-27-2012, 06:30 PM

I am going to see if I can fix it, maybe some JB weld if it is cracked, or some oil resistant epoxy. The weather turned nasty this afternoon so I've got nothing better to do but diddle around in the garage.

wheatfield83 · #9 12-27-2012, 07:04 PM

Right stuff from NAPA is pretty good at sealing stuff like that too. It is a very heavy duty gasket maker.

charmalu · #10 12-27-2012, 11:37 PM

A replacement sending unit from PNP is about $25.00

Charlie

dieselmania · #11 12-28-2012, 10:21 AM

Quote:

Originally Posted by charmalu

A replacement sending unit from PNP is about $25.00

Charlie

I have not been able to find any used parts for my 124 here in Tucson

charmalu · #12 12-28-2012, 01:44 PM

The gasser and Diesel sender is the same part # 124 542 00 04.
so don`t pass on the Gasser 124 when you see them in the yards.

we seem to have a lot of the w124 bodies in our yards out here on the west coast. don`t see the Diesels all that often.

Charlie