Hi,

So, I've been attempting to track down an intermittent fuel smell on my 1970 280se sedan with M130 engine. I climbed down under the car to look at the pump and while the pump didn't seem to be leaking at all, I noticed some weirdness with the fuel lines.

There is a tee in one of the fuel lines attached to the pump and the line that is tee'd off is plugged. I'm kind of baffled as to why this would be there. I took a (admittedly not amazing) photo.



Any ideas?

Also, any ideas on that fuel smell? It's not terribly strong, it seems to be happening while driving, it doesn't seem speed dependent. There is no obvious fuel smell under the hood or any wetness. There was some smell near the trunk and I noticed my locking fuel cap had no gasket, so I added one.

I don't know why that was blinded off. I once had a 280E that would not run until I blinded off one hose. I got a lot of pressure in the fuel tank but I was able to make it home (200 miles) where I just replaced everything.

As far as the smell: Those fabric wrapped hoses will crack inside and fuel will leak out in tiny amounts. But tiny or not the smell will still be there because the fabric covering will soak up the gas and not even appear wet.

As drastic as it sounds I would just replace all the fuel hoses back there. This might sound like a big job but the worst part would be draining the tank. There is really not that much hose to replace. You could also clean the screen and swap out your steel fuel line that runs from the tank to the engine.

And clean everything first at a car wash. By the time you drive home you might be able to see, once everything is clean, where the leak is. And if nothing else it will make the hose replacement easier.

I'd also check the expansion tank and corresponding hoses in the trunk.

Right. For reasons I have never figured out an expansion tank will crack. I guess there are a million things that could cause this.

And all it takes is a hairline crack you would never see. But you can removed the tank, plug all the holes but one with your fingers, and then blow into the remaining open hole. If the tank is not holding pressure you will know.

Could have been used to hook up a fuel pressure sensor; I have an inline tee hooked up to mine so I know if my engine cuts out, I can rule in/out fuel starvation.

It's for diagnostic purposes.

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Current:
1971 Mercedes Benz 250 (Euro Spec)
1972 Mercedes Benz 250 (US Spec)
Past:
1972 Mercedes Benz 280

Which one?

Without knowledge of which line is teed/plugged, it seems quite futile to speculate as to the purpose.

Thanks for the suggestions. I'm going to dig into the tank in the trunk this week. One thing that I'm curious about is where the lines from that tank go? I know that the purpose of the tank is to send fumes back up to be burnt in the intake, but where do they enter the intake tract? Is it a hard line or a soft line? I ask because I had an open vacuum nipple on my throttle body with part of white cloth covered hose on it and I'm thinking that maybe that's it?

Also, while I'm at it, there is a sensor of some kind screwed in on the spark plug side of the cylinder head right up near the firewall. Can anyone tell me what this is and what it does?

another remote possibility is the drain hose at your filler.
If damaged it can leak fumes etc into the trunk as mine did.

that tee looks like its on the fuel return. The v8 cars have a bypass there. I don't recall the straight-6 cars having one. But's been a while since I had one.

The sensor on the block should be a temperature controlled switch. It has two wires with two different size connections on it?

As opposed to the temperature guage's feeler that looks like its a tiny tube with a wire mesh around it.

-CTH

__________________
- cth350@gmail.com
http://www.111lakeside.com/