new W116 fuel hose, strainer and filter

I recently purchased a W116 280SE.   On arrival, it wasn’t running too well, and the symptoms pointed to the car not getting enough fuel.    A few weeks ago, I drained all the fuel in the tank and checked the main fuel filter and strainer.    After doing all this, the fuel filter and strainer were all that bad.   They certainly didn’t look bad enough to make the car run the way it did.

I figured I would be doing a fuel volume and pressure test next.   Before I got to that though, it seemed to make sense to install a new W116 fuel hose, strainer and filter.   These parts are all still available and not super expensive.   The hoses get very hard and brittle, and as they are cloth covered, it can be difficult to see their condition.

I probably could have just cleaned the strainer, but it was worth waiting a few weeks to change the part and do the job properly.    The Petrol strainer is different to the diesel one (finer mesh) and now carries a 201 part number.    This part comes with a new o-ring.   The old o-ring was almost non existent, another good reason to change this part.

The W116 fuel hose screws into the bottom of the strainer.    Its a W123 part number and actually the same part as required on my 1977 450SLC, so I had one on hand.   I’ve now ordered another one to have a spare for my 450SLC.   The new hose was nice and soft – the old one had become very hard.

After installing the W116 fuel hose, I replaced the main fuel filter.   The new filter helpfully came with some new copper washers.   These jobs are quite easy to do when the tank is empty.    Its also much easier to do with a hoist.   The first time I changed one of these fuel filters, I was using ramps and it was much more painful.   In particular the hoist allows the access to get everything tightened up properly first time.

After I put the car together, I bought 25 liters of new fuel.   I didn’t want to re-use the old fuel as I had a suspicion it wasn’t any good.   I couldn’t really explain why the car ran so much better when I added fuel to the tank previously.   The state of the fuel strainer, and the rate in which the tank drained made it clear the swirl pot wasn’t all blocked up.    One theory was that the old fuel was so bad that adding new fuel diluted the old and allowed the car to run properly.    It did pain me to discard $60 worth of fuel given current prices.

I started the car up and it ran the same as before.   That is, it would idle ok, but the car would stutter if I gave it any throttle.   It did seem pretty clear that the filters were not the cause as had it been a blockage here, it would have run a lot better from the outset.   I still wanted to rule out bad fuel, so I ran the car for a bit longer.   At this point I was pretty confident that I hadn’t fixed the problem, but felt I should rule out the bad fuel on the off chance.

I’m glad I did.   The car started running better and better.   I ended up taking the car for a 40 minute drive around the local roads.   By the end it was running pretty well.   Not perfectly, but quite well.   Idle was still a bit high, but this may be to do with the cracked exhaust y-piece.   I live in a very hilly area and I was soon able to drive up hills, kicking the car down and not having any stuttering or hesitation.   The throttle linkages and kick down are adjusted properly on this car.   Its quite common to find they are not.

I didn’t push the car too hard as it was raining, I don’t know the car yet, and the tyres are a bit old.  My test drive allowed me to drive on a couple of 80km/h roads to put the car through its paces.   I am going to have to fix the steering coupling before I drive this car too much, as its quite bad.   The exhaust leak is also something that will need attending to.    Next step though is to do an oil/filter change and change the shift bushings.

So far at least, It looks like the running issues for the car were caused by bad fuel.   I have two theories as to why that is.   First one is that the car had been filled up with e10 and then not driven much.   The ethanol attracts water and doesn’t store well.   The other is that somebody wanted to buy the car cheap at the auction and sabotaged it.    I’ve heard of this happening, although I think the first theory is the most likely.   E10 is pretty nasty stuff and has no place in anything but a rental car.

On the test drive, I noticed that the design of the W116 allows you to drive in the rain with the windows down, and have little to no water get into the car.   Its quite a nice feature that modern cars don’t have.