Metal fuel line rusty?

[Scutch]

I keep finding little pieces of sediment and what seems to be copper colored metal fillings in the bowl of my Zenith Carbs. I have a fuel filter just before the mechanical fuel pump and when I change it, it never seems to be that dirty.

Is it possible that the metal fuel line from the pump to the carbs is the source of my contamination?

Does anyone have a clean one they would sell me? Are they expensive from Mercedes?

Thanks
Eddie

[Mike D]

What's the status on your mechanical fuel pump? New or old?

The only place brass/copper is used would be in the in-tank screen (any of those particles should be trapped by the in-line filter), the fuel pump itself (this would be my first choice of a suspect) or the fuel inlet fittings/needle-seat assemblies on the carbs themselves.

Have you noticed an increase in either oil consumption or oil full level?

Use a magnet on the filings. Rust is magnetic, copper is not.

[Scutch]

The fuel pump is a few years old. You think something is grinding in there and being spit out? Seems like there is just an in/out motion. Doesn't the fuel go right by any of the inner workings of the pump? It just contacts the diaphram, right?

Also the debris is a mix of stuff. the copper colored stuff is just easiest to see. Some is grey and some is black.

Does anyone have experience with that curved metal fuel line that wraps around the valve cover being rusty and producing contamination?

Is there any reason not to just replace it with rubber fuel line and connect the ends to the metal parts that need to fit into the carbs?

[Mike D]

No problem with replaceing the steel with rubber as long as you ensure the rubber is adequately protected from rubbing.

Diaphragms are rubber (black) with a large central disk (gray) which is held into place by a rivet (brass). The center shaft (gray) runs through a bronze bushing (copper colored) in a cast metal housing (gray). It may have one or two "one-way" valves (black) mounted in either a brass or metal (gray) fitting.

Use a magnet to determine the composition of the filings.

The black can also be from a rubber line breaking down internally.

[todds]

I had a similar problem, ended up coming from the tank. The bowls were full of a reddish sludge that turned into a reddish powder when it dried out. I guess it made it past my fuel filter/pump, strangely. Changing lines/pump/etc made no difference as my Webers sludged up after about two days of driving as well, the only cure was a tank refurb. Not cheap, but the problem went away for good and my gas is nice and clean.

If you don't want those metal lines, don't toss em! I'll take em!

[ctaylor738]

Don't the Zenith's have a brass filter in the carb where the fuel line attaches?

[Scutch]

There is no brass filter on the carbs anywhere. I have now put a filter on before the fuel pump and after, just at the carbs and still there is black stuff in the bowls. I think it is debris from the paper gaskets from taking the carbs apart so much. On another note. I just realized that all of the "carb" problems I thought I had was from a Bosch plug wire that went bad after 1 year. That was unlucky and cost me a lot of unnecessary suffering and contempt for those Zenith carbs. Turns out they aren't so bad after all.
What kept me on the false trail was that almost everytime I took the carbs apart. I saw debris in the bowls. When I cleaned them all out and put them back together they almost always ran with no problems for a day or two.
Why? I don't know.

[todds]

Hmm, could be just extra design tolerance making up for failures. It takes a few things happening together to cause them to stop running. I'm sure the fuel and ignition was built with some leeway in there. I know that my Zeniths were still running with over 1/2 inch of powdery sediment clogging god knows which passages. Took a big piece of missing gasket on the bowl and corresponding massive fuel leak into the carb throat to kill the engine's ability to idle. I guess one advantage to dual carbs is if one of them is compromised in some way the other one can make up for it to an extent.

Could be that you happened to move or shake the bad cable while working on the carbs too. An inline six can run surprisingly well on 5cyls if compression and fuel are perfect and especially if the miss is only occasional.