Fuel Starvation and poor running

[c107]

Was talking to Syria today and he has been trying to get his gold 450SE driving again and was having a problem where it would start and run very poorly.

Thinking about this I was wondering if it might be a similar problem as one I had on my old 250SE Coupe.

When I bought the car, it would get to the point where it cut out and ran poorly, but not all the time. At first, I thought that I had a bad fuel pump that would not provide the necessary flow when hot. The fuel pumps on the old MFI motors are very expensive so I was keen to make sure the problem was elsewhere before I looked at the pump.

The car had sat for some years before I purchased it and it turned out the problem was a blocked hole in the fuel bowl inside the fuel tank.

if you have never looked inside one of those tanks, there is a plastic structure that looks somewhat like a flower pot. the purpose of it is to allow the car to corner and go up/down hills without the fuel sloshing around and causing fuel starvation.

The pickup for the fuel is inside the bowl (and goes through the fuel screener) and the return line swirls around the bowl. There is a small hole in the bottom of the bowl and due to the venturi effect, once the fuel level is below the level of the bowl, fuel transfers into it through this hole.

This small hole gets blocked on cars that sit for a while and even after cleaning the fuel screen and fuel filter, once the fuel level goes below the bowl, the fuel cannot easily get in and the car cannot get enough fuel.

To fix the problem, I dropped the tank and used a series of pipe cleaners, toothbrushes, clean fuel etc I was able to clean out the bottom of the bowl opening the hole again.

This also freed up some of the other gunk in the tank so despite the cleaning, after driving for a tank or so of fuel, I changed the fuel filter again and the car was fine after that.

The swirl pot is delicate so you can't just let any old radiator place use aggressive cleaners on the tank because if it is dissoved or damaged the fuel will slosh around - anyone cleaning the tank needs to do it in a way that preserves the pot.

Now I know this pot exists in all the fintails and derivatives (i.e 108,109,110,111,112,113 etc), and I hear from forums it existgs in the 107 so I assume it exists in 116s too.

 

[c107]

Confirmed W116's should have the swirl bowl.

 

[motec 6.9]

I have recently had to fix my C-10 fuel tanks for causing the same issues. Will load pictures after I finish work. After cleaning tanks need to reseal with POR15

 

[c107]

I have recently had to fix my C-10 fuel tanks for causing the same issues. Will load pictures after I finish work. After cleaning tanks need to reseal with POR15

at least on the Mercedes you need to be careful you don't seal the little openings in the swirl bowl with POR-15. A few people have found this out the hard way. O

ther cars have a simpler system and the POR-15 works well on those tanks. For example, by Jag has a 'sump' that screws into the bottom of the tank, and the fuel pickup with strainer is longer than the tank is high so goes down into this sump. It means the sump can be simply unscrewed from under the car (it actually sticks out through the sheet metal) cleaned and then put back in.

 

[Styria]

C107's thread can be associated with my futile attempts to get my 450SE running after a number of months of inactivity. Incidentally, Bryce's findings and experiences can in fact be quite common problems found in 108s and 109s, and I know of one instance with another 108 owner who had two fuuel tanks afflicted with the sort of problems Bryce has enumerated on. That owner's solution was to have the tank(s) cleaned with acid by a Company called Redi Strip located in Blacktown. Apparently that solved his problems, after he had tried new fuel, new filters etc. etc. and hours of stuffing about. I will get back to my 450SE in another post, and also have a short, but ever so frustrating story to relate to my Rover P5 3 litre Coupe.

In the meantime, a huge thank you to C107 for his thread -a must read if you're faced with cars that have not been used for a number of years. Regards Styria

 

[c107]

also have a short, but ever so frustrating story to relate to my Rover P5 3 litre Coupe.

Hope no major problems with your rovers!

 

[Styria]

Sorry to be a bit slow to respond. I have three Rover Coupes that I am presently restoring, and the last time I had done any serious work on the three cars was probably about twelve to fourteen years ago. The work at the time included: Rebuilding of engine, gearbox and differential.
Rebuilding of front and rear suspension
Re-upholstery in leather - Mark III and Mark IIC in Austrian
Schmitt Wallsdorf leather.
Mark IIA - the car referred to herein
Bridge of Weir Scottish Hide.
New carpets of course, not yet totally finished.
Full respray in 2-pack.
Webasto Sunroofs in Mark III and IIA - $2000.00 each car.
Plus, plus, plus - you name it. Those are just some details.
Anyway, I stopped using the car probably about 1976 - it was replaced by a Rover 3500S, and then, in 1979, the aforementioned MarkIII joined the stable. So, Petrol in the car was about forty years old - I mean there wasn't any except for the horrible smell of old petrol, and what turned out to be a ` black, crusty substance inside the tank.

Obviously, some serious remedial work became the order. I must have cleaned out the tank with huge quantities of Kerosene, Petrol, Kerosene, Petrol (not necessarily in that order), but really my efforts produced very little by way of satisfactory results. The black, sooty stuff just kept on coming, and coming.... In the end, I entrusted the work to Redi Strip at Blacktown, and they had three attempts to chemically clean the fuel tank with fairly good results - but, they had three goes at it, but luckily they only charged me for the initial clean - $200.00. I can recommend them, as they did not shirt the task of repeat cleans.

Presently, the tank is sitting on the bench, with twenty litres of oily Kerosene to stop any further development of rust. I only just had another clean out yesterday and, believe it or not, there are still slight amounts of black sediment that keeps coming out. I will probably have two more attempts at swilling out the tank before I re-install it in the car. What's the moral of the story ? Don't wait forty years before you attempt to restore a car. Regards Styria

N. B. I thought it might be a good idea to marry these two threads. There are some pertinent similarities.
http://www.topklasse.org/forums/showthread.php?t=4143

 

[Oversize]

Wouldn't it just be easier to cut a hole in the top of the tank large enough to clean it properly??? Obviously done by a professional to avoid fatal blow-ups....

 

[sean sherry]

On the ball Mark, much easier and cheaper to cut the top of the tank off. My 107 cost about $120 It turned out to be a waste of time to clean, as the tank was like new inside. Though I did stop an annoying noise as the tank ran low... a broken piece from a previous fuel sender unit rattling around.

 

[Styria]

Wouldn't it just be easier to cut a hole in the top of the tank large enough to clean it properly??? Obviously done by a professional to avoid fatal blow-ups....

Mark, I had given serious consideration to do just that - obviously, if one can get their mits into the tank, a successful clean may be the reward. However, I have been somewhat reluctant to do just that - I used to have a really experienced welder to carry out this work for me, but he passed away a couple of years ago, and the alternative guy I have is super cautious about doing this sort of work.

I wish I could look into the tank properly, as there are any number of baffles that are part of the inside workings. In an effort to try and come up with a satisfactory solution, I have purchased two additional tanks just the other day - at $50.00 each on the premise that they are in good condition. The first one, tackled today (of sorts), is probably no better than my tank when I started with it. Anyway, all this hassle with "old fuel" in the 450SE, and now the tank saga, made me take "Gleaming Beauty" for a 40 kms. drive (absolutely no issues), but I also completely ran the tank dry and refuelled with brand new 98 octane petrol. Regards Styria