I'm doing an underbody restoration on my '94 500 and of course now my fuel pumps (two on this older car) look scrappy. If I convert to single pump you can do away with all the metal lines and banjo bolts. All being rubber hose connections.

However, having had two newer (99/2000 MY) R129's I think there has been an unusual vent pipe from the fuel filter.I think this little press-on (no clamps/unions) pipe joins the fuel vent system to the charcoal canister. However I don't know where it links in, and have also just appeared to discover that the newer cars don't have the plastic vent valve just below the tank vent outlet. I wonder if something else gauges fuel tank pressure/when to allow vapours out..

From what I gather, 500E's/124's that were converted to single pumps DON''T have this vent pipe from the fuel filter that 129's seem to have, hence my post.

So, I'm just wondering if anyone has done the conversion on an early R129 and is familiar with the above regarding this unusual vent pipe from the newer fuel filters.

Thanks

Here’s a parts image. Pipe 180 “from filter to breather line”

I’ve replaced my white plastic tank vent valve (just below tank) BUT as far as me linking a filter breather line in, it appears newer cars don’t have this plastic vent valve under the tank anyway (where you could join). But does breather pipe 180 still join in the same place beneath the tank?

So, why do late 129 cars seem to have the fuel filter breather but why would other single fuel pump cars not incorporate it? Maybe it’s just an M112/M113 thing?

Also it appears newer cars don’t have the white plastic vent valve just below the tank so how do they know when to vent pressure to the charcoal canister? (I could be wrong about this but a guy I know is working on a late silver arrow and he says he doesn’t have this valve)

If anyone can help shed light on it I’d be pleased to know, particularly if I want to convert to a single pump set up.

thanks

Pics to help/clarify. 1st diagram is older car.

newer cars don’t seem to have the (no 8) vent valve my older car does.

It does appear the fuel filter vent pipe joins the vent system under the tank (see T pipe no 30).

I’m confused because I thought the plastic vent valve (no 8) actually controlled fuel vapour to the charcoal canister, yet newer cars don’t seem to have one.I thought it opened to let fuel vapours out of the tank at a certain pressure.
Bottom line. I wonder why the fuel filter has a vent and whether it needs incorporated if changing to a single fuel pump.