Friday, October 22, 2010

W116 Fuel system

I took the trunk panel out to take a look at the fuel tank. It looked brand new, like much of the inside of the car. I didn't get a good description of the problem from the owner or his mechanic, so I located the leak via the 'Pikey' method, which is pour some gas in, see where it comes out. Underneath there are a few fuel system components interconnected by rubber lines. All of these rubber lines were cracked, some broken. I think the life of these lines is somewhere in the 10 year area, so they all needed replacing. All screens, filters and any other consumables are to be replaced too, while I'm at it. The fuel damper, which is a very simple, but expensive piece, had a few pin holes in it from rust. It's supposed to be zinc coated, but I'm sure all that wore off years ago. A brand new damper costs around $90 USD.

The damper's purpose is to even out the fuel pump's surges. It costs as much as a fuel pump, so take good care of it. The accumulator, pump, filter and damper should all probably be replaced, along with all of the fitted hoses. This is not cheap! Its an easy job though, if you have the right tools.
Fuel injection systems generally have a high pressure side (feed to the injector distributor) and a low pressure side (return to the tank). If you are going to remove this system properly, you'll be wanting fuel line nut wrenches. A crow's foot line wrench set is probably the best idea, in 3/8" drive size. You may have to apply a lot of torque and penetrating oil to free the line nuts. I did both, and broke the fuel feed line anyway, so I'm going to replace the feed line entirely. This is what happens when you use vise grips instead of the right tool. Vise grips are a Pikey's tool.

Mercedes are bullet proof. Only rust can destroy them!
Most people who drive old Mercedes say "Oh I love it, it drives like a tank." I've never driven a tank, but I'm sure what they're talking about is the rigidity of the chassis. No cost is spared on the suspension or steering bits. There is only one problem, and that is the problem with all steel, and that is rust. Mercedes in particular have drainage systems that are probably intended for garage keeping and meticulous cleaning and detailing by your driver's assistants. The drains are intended to keep water away from the frame and body, and of course out of the interior. This all works great until the drain tubes become clogged. Just like the leaves that clog your downspouts, these things must be kept clear. If they are not, then water finds its way into places it shouldn't, like the trunk, tops of the wheel wells, lower door areas, etc. I have probably 6 months of welding, grinding and finishing to do on this car due to poor maintenance of drains and bad prior body work. Normally I'd stay away from body work, as it's just never good enough and can't be done right in a rush. That and all body men are miserable, humorless, violent ex-convicts, constantly covered with a toxic miasma of body filler dust, solvents, primer and paint wastes. No matter how good a car looks, once you start chipping at the rust you end up with big areas which need cutting out and replacing.