w123 280ce tank return pipe orifice clogged
 

My brother is resurrecting a euro 280ce. There is an orifice in the tank return pipe that is clogged. Any thoughts on how best to tackle this ? The tank is out.

Compressed air?

No joy on using either pressure or vacuum to clear the blockage. My brother has a good 240d tank, but it doesn't have the orifice. I can make something on my lathe -- anybody have any idea of the appropriate hole diameter ? Since were 500 miles apart, trial and error would be a slow process.

Geoffrey

gmb:

The opportunity to place ignorance on display cannot be passed up:
Why is there a restriction in the return line? Such has not been observed elsewhere.

This is for a different model, but the problem is the same --

Fuel Tank Strainer, Fuel Tank Insides, Swirl Pot, Return Line Venturi - Mercedes-Benz Forum

The venturi gets clogged -- in this case after sitting for several years. There's no direct access and it can be challenging to unclog.

case closed
 

Using a 2+ foot section of aircraft cable spinning in reverse with a drill succeeded in rooting out the blockage.

There are two holes really. The one in the jet and then the aperture around it. The return line jet causes fuel from bottom of tank to be sucked into the swirl pot. The jet can be cleaned as you described by rodding it out. But the aperture around it is hard to get at. When that is blocked, cars have been known to run out of fuel when level gets to below the top of the swirl pot.

This Pelican link is about the Porsche swirl pot which is similar, but not exactly same as those on Benzes. It has pics that show the fuel entry aperture adjacent to the return line, more clearly.

CIS Gas Tank - Pelican Parts Technical BBS

This thread prompts a question:
What chassis and engine combinations were fitted with tanks which included a swirl pot?

At least R/C107s and W123s. Probably most Benzes of that era? Gassers at any rate.

The OP indicated that an available 123 diesel tank did not have the "restriction" feature.
How about carbed gassers? Return flow is very small.

He didn't say what year, but if tank has a fuel return nozzle, it would likely be a Kjet. Presumably all kjets and djets had that system.

From my random reading on the subject I too think the swirl contraption is a petrol fuel injection addition (so I don't think carbs and diesels have it)

Yes, it seems one of it's functions is to mix the hot fuel returning from the engine bay with cooler fuel in the tank. Most of these early fuel injected cars had a hot start problem and this probably helped. Porsche and others used a similar set up.

I reckon it is a Bosch CIS thing - probably find a similar system on Ferraris and Lancias too!

And yet, what is probably the largest single marque installed base, Volkswagen w/K-jet, et. seq., seems not to use the device!