#fuelstrainer

In the last update, I ruined my W123 fuel tank.   Luckily, a friend in the Mercedes Club was able to find me a very good tank as a replacement.   The new tank is much better than what I had, and probably far better than a home resealed tank.   It was from a 280E, which means it is an 80 litre tank.   I will have excellent range on my 240D.

The main difference between a tank from a petrol W123 and a diesel is the petrol cars had the swirl pot at the bottom of the tank.   The swirl pot allows fuel to continue to flow even during hard cornering, as the return line not only keeps the pot filled, but draws fuel in from the rest of the tank.  Presumably the diesels don't need this as they flow a lot less fuel and are less likely to do hard cornering.   In addition, an algae outbreak could clog up the little hole in the bottom of the pot.   I'll be using the biocide additive on my car regularly, so I'm not concerned about this.

When the tank arrived, I was really impressed with how clean it was.  I couldn't see any rust at all in the tank. The petrol fuel strainer was also quite clean.  Since I don't want to do this job again, I gave it a clean and was able to get some of the normal residue out of the tank before installing it.   I used my pressure washer to clean inside the tank as best I could, then dried it with my cordless blower.   After that, I used some methylated spirits to make sure I got the last of the water out.

I came back the next day to prepare the tank for installation. I installed a new diesel fuel strainer.   The diesel strainer has a coarse mesh, to allow minor algae to get through and be caught in the pre-filter which is easier to change.   This is part 124 470 01 06.   I also re-installed my fuel sender.   Mercedes thoughtfully made both of these items use the same 46mm hex.   I also had to glue on the rubber 'foot' that sits around the strainer and between the tank and the body of the car.

Re-installing the tank was easier than getting it out.   The only slight hiccup was the rubber 'foot' had been somewhat dislodged and I had to use screwdrivers to reposition it from under the car. Once the tank was in place, it was a fairly simple matter to install a new fuel supply hose.  The car was using the fitting from the original hose, with a normal fuel hose clamped to it.  There probably isn't anything wrong with this, but I bought the proper cohline hose.  It is for multiple cars, so I had to trim a few cm off for the W123 diesel. Next was the return line and breather hoses.   The EPC states that these hoses are both 120mm.  I cut 120mm hoses, but I found the return hose was too long and I trimmed a few cm off it.   The breather hose was also thicker.   I didn't actually install the breather hose at first, I waited until I had the car running so I could move it to the hoist under its own power.   I had bought the proper hose clamps for the engine bay and the supply hose, but forgot these two, so had to use the regular hose clamps here. While I was at it, I also replaced all the hoses and filters in the engine bay.   The pre-filter was quite dirty, and needed replacement.   The main filter probably wasn't, but I replaced it anyway.  I also used the proper hose clamps that don't bite into the hoses.   According to the EPC, the hose from the supply line to the pre-filter is 140mm and the hose from the pre-filter to the lift pump is 40mm.

The EPC also lists a special return hose some people refer to as the 'Cigar' hose.   This is part number 000 997 51 52.  A lot of people don't seem to bother with it, but since I was ordering new parts I got one.  I found it to be very long, and I had to push it a long way onto the return hard line so it didn't kink. At this point I was ready to refuel the car.  I had 30 liters of diesel I had pumped out of the car through a filter, so I added this to the tank.   I was happy to see there were no leaks and I began to prime the system.

The primer pump felt very odd, and I couldn't work out why it didn't seem to be moving much fuel.   After about 30 minutes of trying various things, I noticed that one of my hose clamps was stopping it from going all the way in.   Simply rotating this clamp restored full travel to the primer and I was able to get quite a lot of fuel moving.   I think my issues priming the system last time were due to my blocked strainer, as I was now getting quite a lot of flow. It still took quite a few times of priming the system, trying to start the car, priming the system, and trying the start the car until it finally roared into life.   It ran well and seemed to be idling better than before.  I wonder if it wasn't getting enough fuel with the blocked strainer. A quick test drive around the factory complex showed no leaks and the car running well.   The downside was that the A/C had stopped working, which I will need to attend to. Since I was happy with how the car was running and there were no leaks. I re-installed the boot trim, and left an Easter egg for a future owner on the fuel tank.

Over the last few months, I have been dealing with the algae problem in my 240D.   I've been quite busy with my trip to Victoria and work, so the 240D has been on the backburner.   However, I am keen to get the 240D back on the road, so started work again in the last two weeks. Previously, I had determined that the fuel strainer was blocked and pumped out 40 liters of diesel into fuel cans.  I assumed there was not much left.   My next task was to see if I could remove the strainer. A couple of weeks ago, it was a rainy Sunday and my three kids were bored.  They were keen to come with me to my little warehouse unit and help me out on the cars.   The first step was to get the 240D out and up on the hoist.   The three of them were quite pleased that they were able to push the car out on its own.  Then I showed them how to use the positioning jacks to spin it and position it properly for the hoist lifting arms.

Next was to get the car up into the air and drain the remainder of the tank.  We used a tool to stop the flow of fuel as we disconnected the main fuel hose.  I wasn't sure how much diesel could flow through the blocked strainer, and didn't want a face full of it as I disconnected the hose.  It turns out I needn't have bothered, as only a thin trickle of fuel was able to get past.

We let the fuel drain slowly into a bucket.   We were seeing some debris come out as we drained the fuel, although not a lot at this stage.  I had previously purchased a 46mm socket online.  It required a 3/4" drive, and so I also purchased an adaptor.   Trouble is, I lost the adaptor and so my new socket was totally useless.  By then the kids were bored and we left the car to drain into the bucket.

A couple of days later, I went back and the bucket had just slightly overflowed.  There was more fuel than I figured in the tank, but I was lucky that it was only a tiny bit more, as there wasn't a very big puddle around the bucket.   There wasn't a whole lot of clearance around the strainer, so instead of buying another adaptor, I bought a different 46mm socket that could use a regular ratchet. Even with that and a wobble extension, it was hard to get enough grip on the strainer.  Even when I could, and using a long breaker bar, I was unable to get the strainer to move, the socket would just come off.   I spent (or wasted) two evenings trying various ways of getting the strainer to move. Eventually a friend told me that taking the fuel tank out of his W126 was surprisingly easy.   The W123 is quite similar to the W126 in that regard, so I decided that I would remove the tank. Yesterday I went and started that process.  It really wasn't so bad and I should have done this earlier.   I found this article from dieselgiant the best.   It is quite simple.  While the car was still up in the air, I removed the hoses for the return line and breather.  They were quite hard, so I will replace them.   according to the EPC, they are both supposed to be 120mm in length. Next with the car on the ground, the divider panel comes out with an 8mm socket.  There are four bolts.   There is no need to remove the carpet backing.   Most of the guides tell you that you need to remove the first aid box and disconnect the sender from the top.   I didn't, and it was quite easy to remove it from the boot. It looks like the tank will clear the vacuum reservoir that sits above it, but it won't.   It is held on by a plastic fastener that I removed with a trim removal tool.   There is enough slack in the vacuum line to put the reservoir to the side.   I also found it easier to remove the right hand side boot liner, which is moulded plastic.   There was one plastic fastener below the tail light. Its a bit fiddly to get the tank out due to the filler neck.  I found using a pry bar on the right hand side of the tank, as I pull it out from the left was the easiest thing to do. Once I got the tank out, I was able to use the breaker bar and my 46mm socket to get the strainer out.  It was not easy, I doubt I could have done it from below, had I kept trying.   The fuel sender unit was even harder.

It was also interesting to discover that a used fuel tank was installed some time after 2005.  The replacement tank was removed from a 300D 18/06/05.  It is in keeping with this being a fairly low mileage car that saw limited use.

On removal, it was clear why the car was not running well.   The strainer was coated in black gooey algae.   Its surprising it ran at all!   The sending unit on the other hand was very clean.  On inspection, the sides of the tank are also very clean, there is just a layer of gunk on the bottom.   I used a couple of small brushes I had on hand to clean around the area near the strainer, but I want to find something better before I re-install the tank.    I'm not too keen to use water, as I don't want to contaminate the fuel or cause rust issues in the tank.

My next steps will be cleaning the tank more, and then starting the re-installation. This will include cleaning up the area where the tank goes.